long-term trends and gleissberg cycles in aurora borealis records

Solar PhysicsDOI: 10.1007/----

Long-term trends and Gleissberg cycles in aurora

borealis records (16002015)

M. Vazquez1,2 J.M. Vaquero3

M.C. Gallego4 T. Roca Cortes1,2

P.L. Palle1,2

c Springer

Abstract The long-term spatial and temporal variation of aurora borealis eventsfrom 1600 to the present were studied using catalogues and other records ofthese phenomena. Geographic and geomagnetic coordinates were assigned toapproximately 45 000 auroral events with more than 160 000 observations. Theywere analysed separately for three large-scale areas: (i) Europe and North Africa,(ii) North America, and (iii) Asia. Variations in the cumulative numbers ofauroral events with latitude (in both geographic and geomagnetic coordinates)were used to discriminate between the two main solar sources: coronal massejections and high-speed streams from coronal holes. We find significant long-term variations in the space-time distribution of auroras. We mainly identifythese with four Gleissberg solar activity cycles whose overall characteristics weexamine. The Asian observations are crucial in this context, and therefore meritfurther studies and verifications.

Keywords: Solar activity, Solar cycles, Geomagnetic storm, Aurora borealis

1. Introduction

During the last few decades a network of ground- and space-based instrumentshas monitored in detail the interaction (compression and magnetic reconnection)between the solar wind and the Earths magnetosphere (see Saiz et al., 2013).Especial care has been devoted to the transient events (geomagnetic storms),that configure the space weather. The process behind these events has threemain phases: (i) the solar sources of energetic particles flares, coronal mass

1 Instituto de Astrofsica de Canarias, 38200 La Laguna,Spain. email: [email protected] Departamento de Astrofsica, Universidad de La Laguna,38205 La Laguna, Spain.3 Departamento de Fsica, Universidad de Extremadura,Avda. Santa Teresa de Jornet 38, 06800, Merida, Spain.email: [email protected] Departamento de Fsica, Universidad de Extremadura,06071 Badajoz, Spain. email: [email protected]

SOLA: VVGTP2015v8.tex; 6 January 2016; 14:42; p. 1

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ejections (CMEs) and coronal holes; (ii) the interplanetary magnetic field (IMF)configuring the heliosphere; and (iii) the consequences of the impact on theterrestrial magnetosphere and atmosphere which may give rise to a geomagneticsolar storm, generally favoured by a southward polarity of the IMF. Close cor-relations between the three phases have been found (e.g., Tsurutani et al., 1997;Kamide and Maltsev, 2007; Richardson and Cane, 2012; Lockwood and Owens,2014). Auroras are a manifestation of this process in the Earths atmosphere.Since they are easily visible without instruments and occupy a large angularextent of the sky, their occurrence can be tracked over several centuries on thebasis of not only scientific observations but also popular reports. See Chapman(1970), Siscoe (1980), Silverman (1992), Feldstein et al. (2014), and Akasofu(2015) for reviews, and the monographs of Eather (1980), Akasofu (2009), andVaquero and Vazquez (2009).

Frequency of aurora occurrence can be used as a proxy to study the past be-haviour of solar activity. These proxies have a longer coverage than sunspots andgeomagnetic indices, and a better time resolution than provided by cosmogenicisotopes (14C, 10Be). The main disadvantage of using auroras as a proxy of solaractivity is their dependence on the conditions of the IMF and the inhomogenityof the records, both in space and time. One must also take into account thewarning of Riley et al. (2015) that if no aurora was reported, it may or may notmean that none occurred. The same applies to sunspots, meaning that theseparameters lead to underestimates of the geomagnetic activity.

The visibility of auroras is limited to ring-shaped regions around the geomag-netic poles the auroral ovals centred at around 65 degrees magnetic latitudein each hemisphere (Feldstein, 1963). Viewed from space, auroras are diffuseoval rings of light around the geomagnetic poles. Under the impact of a solarstorm, the auroral ovals undergo broadening, particularly on the night side. Allof the great auroral expansions have been associated with intense values of theinterplanetary magnetic field (Sheeley and Howard, 1980). The variation of theradius of the auroral oval in response to solar wind changes has been studied byMilan et al. (2009).

Low-latitude auroras are very rare, and are clearly associated with stronggeomagnetic storms produced by solar coronal mass ejections. They are generallyred and diffuse, resulting primarily from an enhancement of the 630.0 nm [O i]emission due to bombardment by soft electrons (

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compiled 42 Chinese and Japanese auroral observations during the period 1840 1911, and found that at least 29 of the 42 observations (i.e., 69%) occurred attimes of weak to moderate geomagnetic activity. See also Vaquero, Trigo andGallego (2007) and Vaquero, Gallego and Dominguez-Castro (2013) for recordsfrom the Iberian Peninsula and Mexico, respectively.

The visual sensitivity thresholds of the green and red radiation of the aurorasare between one and ten kilorayleighs, which means that only those auroras com-ing from moderate and strong geomagnetic storms will be visible and thereforecome to form part of our sample (Schroder, Shefov, and Treder, 2004). It is clearthat the meteorological conditions also play a role, although a cloud-free sky isnot necessary.

Fritz (1873) produced the first graph showing the geographical distributionof auroral frequencies, measured in nights per year. The values ranged froma minimum in the Mediterranean area to a maximum at a magnetic latitudeof 67 degrees. According to Livesey (1991), the zone with the greatest auroraborealis probability passes across northern Norway, over to Iceland, south ofGreenland, and over to the south of Hudson Bay in North America. In previ-ous articles (Vazquez, Vaquero and Curto, 2006; Vazquez and Vaquero, 2010;Vazquez, Vaquero and Gallego, 2014), we started with studies of low-latitudeevents available in the Spanish documentary sources. In Vazquez, Vaquero andGallego (2014), we began on the task of constructing a global catalogue showingthe results for the period 1705 1905. We applied a method to discriminatebetween the solar sources of the auroras based on the variation with latitude.Low- and mid-latitude auroras are well correlated with the solar cycle, indicatinga CME source. On the contrary, high-latitude auroras are anticorrelated with the11-yr cycle, pointing to a source in the high-speed streams coming from coronalholes. The critical geomagnetic latitude separating these two sources was foundto be located at around 61 degrees.

In the present communication, our intention is to update this catalogue andto extend the coverage to the period 1600 2015, thus including several dis-continuities in solar activity. Our main challenge now is to provide a 3D map(geographic/geomagnetic coordinates plus time) of the auroral activity in thepast, when auroral observations constitute the only information available aboutheliospheric activity. So far as we know, it is the first time that this task hasbeen attempted, because previous work has mainly been based on the numberof auroras and/or on limited regions of the Northern Hemisphere. Our finalchallenge will be to investigate the main characteristics of the last Gleissbergcycles of auroral activity, including the Maunder Minimum. In short, we areinterested in the space climate during the last 415 years.

2. The auroral catalogue: general characteristics

For the present work, we selected the geographical coordinates of every siteat which an aurora had been visible. This allowed geographic coordinates to beascribed to each observation. If necessary, a selection was made from the existingsample to give the broadest coverage in both longitude and latitude. When more


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data were available for an auroral event, all of them were included, combining thedifferent sources, except that very close sites were only represented by one record.Indeed, in general, we tried to exclude from our catalogue any multiplicity dueto sites that are near together, say, differing by less than one degree in position.Figure 1 shows the histogram of the number of observations per auroral event.Broadly speaking, the more powerful the event, the more observing sites therewere per day.

0 2 4 6 8Number of Sites per Day

0.0

0.1

0.2

0.3

0.4

0.5

Rel

ativ

e F

requ

ency

Figure 1. Histogram of the number of available observations per auroral event. Those eventswith more than seven observations are included together under the number 7. Blue: Europeand North Africa. Red: North America.

The number of nights in the period studied (1600 2015) was approximately125 000 (400 years)1. Therefore we have a coverage of approximately 35% of theavailable nights. The available data for the Northern Hemisphere were dividedinto three continental domains corresponding to Europe (and North Africa),North America, and Asia. Table 1 lists the numbers of observations and auroralevents for each of these continental domains.

The first sources of data for the earliest centuries of our sample were the cat-alogue of Fritz (1873) and the archives of S. Silverman2. Fritzs North Americandata are mainly based on the earlier catalogues of Lovering (1866) and Loomis

1We have excluded those summer days in high latitudes, where the aurora borealis cannot beseen.2These include: (i) the Catalog of Ancient Auroral Observations, 666 BCE to 1951; (ii) theAuroral Notations from the Canadian Monthly Weather Review; (iii) the New England Auroral


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Table 1. Total number of auroral events and observations in thethree domains of our sample.

ZONE Auroral events Number of observations

EUROPE 39 612 80 132

NORTH AMERICA 32 600 79 752

ASIA 1 195 2 321

(1860, 1861). They are complemented for the later phase of the 19th centurywith data from Greeley (1881).

For Europe, the Fritz data were complemented with additional values for highlatitudes from Rubenson (1882) and Tromholt3 (1898). Particularly relevant arethe Greenland observations contained in the Fritz catalogue and the Silvermanarchives (see Stauning, 2011). For the rare low latitude observations, we alsoincluded data for the Iberian Peninsula4 and the Canary Islands (Vazquez andVaquero, 2010).

Some of the early Arctic expeditions in Canada and Alaska did not keep anappropriate record of the aurorae boreales that were observed5. On the contrary,only a few cases of low-latitude events have escaped detection, and events of thattype have often been described in historical reports and/or scientific papers.

The data sample is clearly inhomogeneous in both space and time. This re-flects not only meteorological variations but also the difficulties of access to someregions with the consequent low population density. This is especially notablefor Asia, where large areas are practically unpopulated. For North America,there are many temporal gaps up to 1746, and, after that, no data are availablefor the years 1754, 1755, 1756, 1766, 1799, 1810, or 1812. There is a remark-able contribution for the entire period studied from numerous forts (more than60) located along the borders of the expanding settlement of the western andnorthern territories. Therefore, we assume that an aggregated data set, as is thepresent case, would give the same result as an integrated data set (see Silverman,1985). Indeed, this is an approach that we have to take in order to handle theextended period of time we are trying to cover.

For the 20th and 21st centuries, we have included many other sources (seeTables 2 and 3). A non-negligible part of our data comes from popular media ofdifferent types, such as newspapers and, in the last decades, internet resources.

Observations (1720 1998); and (iv) the Daily Auroral Reports Southeastern Canada andNortheastern US (1848 1853).3For a biography of S. Tromholt see Moss and Stauning (2012).4These include published data from Vaquero, Gallego, and Garca (2003), Vaquero and Trigo(2005), Aragones Valls and Orgaz Gargallo (2010), and Vaquero et al. (2010).5This phenomenon having been described by many authors, some of whom have exhaustedthe powers of language in the elegance of their representations, renders it unnecessary for me toattempt any general description of this interesting spectacle. W. Scoresby (1820) The ArcticRegions, Vol. I p.416. See also C.I. Jackson (2013) The Voyage of David Craigie to Davis Straitand Baffin Bay (1818), The Journal of the Hakluyt Society.


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Table 2. Catalogues used for the auroras observed in Europe. BAA stands forBritish Astronomical Association, and WDCA for World Data Center for Aurora,Japan. The Observatories Year Books, containing auroral observations, were pub-lished by the Meteorological Office. The archives of S. Silverman are available athttp://spdf.sci.gsfc.nasa.gov/pub/data/aaa historical aurora/

Reference Start-End Observations

CONTINENTAL

Fritz (1873) 16001874

Link (1964) 16001700

Angot (1897)

BAA 19702008

WDCA, Japan 19571974

Space Weather 2000

REGIONAL

Sweden Rubenson (1882) 17161877

Norway Tromholt (1898)

Finland (all-sky) Nevanlinna and Pulkkinen (2001) 19731997

Finland Finnish Aurora Observers 2000

Denmark Lassen and Laursen (1968) 19601966

Netherlands Visser (1942) 17321940

Hungary Rethly and Berkes (1963) 15231960

Croatia Lisac and Marki (1998) 17371991

Iberia Aragones Valls and Orgaz Gargallo (2010) 1700

Germany Schroder (1966) 18821956

Polarlicht Archive 1938

United Kingdom Obs. Year Book 19231964

LOCAL

Berlin Kassner (1941) 17071770

Sunderland, UK N/A (1902) 18601900

Stroud, UK Harrison (2005) 17711805

Canary Islands Vazquez and Vaquero (2010) 17702003

For publications with an especial emphasis on low-latitude aurora observations,see Gartlein and Moore (1951), Tinsley et al. (1986), Vallance Jones (1992), andShiokawa, Ogawa and Kamide (2005).

Figure 2 shows the locations of auroral observations, on a Mercator pro-jection, of the Northern Hemisphere. The map clearly mimics the distributionof the human population in the Northern Hemisphere6. Tables 4 and 5 list theregions where most auroral events were reported for Europe and North America,respectively. The number of sites is clearly low for Eastern Europe, as it also wasfor Asia.

For the Asian data we used data from the sources listed in Table 6. We shalldiscuss these events in detail later in the paper.

6See one of the pictures of Earth at Night.


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Table 3. Catalogues used for the auroras observed in North America. BAA stands for BritishAstronomical Association and WDCA for World Data Center for Aurora, Japan.


CONTINENTAL

Fritz (1873) 16001874

Greeley (1881) 18731879

Silverman

BAA 19702008

WDCA 1957

Different Reports 16002015

Space Weather 2000

REGIONAL

Canada Broughton (2002) 17691821

THEMIS/GAIA Keograms Mende et al. (2008) 19972015

Polar Years Vestine (1944) 19321933

LOCAL

Washburn Observatory Lueders (1984) 18591884

Harvard Observatory Bond et al. (1889) 18401888

Yerkes Observatory Barnard (1902) 18971902

Barnard (1909) 19021909

Blue Hill Stetson and Brooks (1942) 18851940

Jericho, Vermont Silverman and Blanchard (1983) 18831931

Edmonton Milton (1969) 19531961

Milton (1962)

Table 4. Regions and countries where auroras were most frequentlyobserved in Europe. Balkans includes the following present countries:Slovenia, Croatia, Bosnia-Herzegovina, Serbia, and Montenegro. Cen-tral Europe: Austria, Czech Republic, Slovakia, and Hungary. BlackSea: Bulgaria, Romania, and Turkey. Finally, Macaronesia includes thearchipelagos of the Azores, Madeira, and the Canary Islands.

Greenland 9589 Scotland and North Sea Islands 9047

Fennoscandia 9079 Southern Scandinavia 8487

Iceland 4787 England and Wales 2956

Germany 2643 European Russia 1825

BeNeLux 1710 France 1244

Central Europe 655 Ireland 516

Poland 523 Italy 481

Arctic Islands 342 Switzerland 215

Iberian Peninsula 155 West Atlantic (ships) 134

Baltic States 54 Greece 49

Balkans 52 Black Sea 26

Macaronesia 14 North Africa 13

Malta 3


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Table 5. States (US), provinces and territories (Canada) in whichauroras were most frequently observed in North America. NewEngland includes Massachusetts, Maine, New Hampshire, Vermont,Connecticut, and Rhode Island.

New England 6818 Ontario 5882

Quebec and Eastern Canada 4896 North Dakota 4900

Manitoba 4191 Alaska 4106

Alberta 3926 Montana 3043

New York 2575 Wisconsin 2437

Saskatchewan 2343 Minnesota 2196

Northwest Territories 2155 British Columbia 1474

Nunavut 1220 South Dakota 1134

Michigan 1043 Iowa 951

Ohio 898 Pennsylvania 763

Virginia 727 Washington State 552

Wyoming 544 Nebraska 526

Illinois 516 Missouri 523

Indiana 449 Idaho 309

Colorado 278 Kansas 266

California 194 Oregon 104

North Carolina 109 Nevada 95

Texas 94 Tennessee 91

Kentucky 57 Arkansas 53

South Carolina 50 Utah 41

New Mexico 39 Alabama 36

Arizona 37 Oklahoma 33

Eastern Atlantic 32 Western Pacific 10

Florida 32 Caribbean Sea 24

Mexico 16 Hawaii 2

Table 6. Catalogues used for the auroras observed in Asia. WDCA stands for World DataCenter for Aurora, Japan.


CONTINENTAL

Fritz (1873) 16001874

Silverman

Different Reports 16002015

REGIONAL

Korea Xu, Pankenier and Jiang (2000) 16001662

Korea Lee et al. (2004) 11051779

Arab Countries Basurah (2004)

China, Korea, and Japan Yau, Stephenson and Willis (1995) 1770

China and Japan Willis, Stephenson and Fang (2007) 18401911

Willis, Henwood, Stephenson (2009) 19572004

Willis et al. (2005) 1910

Siberia WDCA 19571962


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Figure 2. Sites, indicated by black bullets, where auroras were visible at least once inthe Northern Hemisphere during the period studied: 1600 2015. The Mercator projectionexaggerates the areas close to the geographic pole.

The histograms of the latitude distributions for Europe and North America(Figure 3) both suggest a bimodal distribution, with the maxima at middle or athigh latitudes for North America and Europe, respectively. The expected trendwould be more auroral events observed at high latitudes, but in the case ofNorth America the histograms clearly reflect the slowly progressing settlementof the northern areas. Examples are the northern US states of Oregon and Idahowhich present relatively few reports due to this population effect. Also, access tosouthern data was delayed until these regions (Louisiana, Florida, Texas, NewMexico) were annexed by the USA. A search of 18th century sources in Spanishdocuments would therefore be interesting for this region.

The latitude distribution of the European records shows more discontinuities,reflecting the existence of interior seas (North, Baltic, Mediterranean, etc.).

We checked the relationship between the auroral observations in these cata-logues and moonlight, since an aurora should be easier to observe when there islittle moonlight during the night. In particular, the light of the full Moon wouldimpede the observation of weak auroras. Therefore, we expected relatively more(fewer) reported auroras when there was a new (full) Moon. Indeed, we foundthat there was a clear decline in observed events with increasing brightness ofthe Moon.

3. Latitudinal Variation: Solar Source of the Auroras

As stated in the introduction, the IMF (also called Heliospheric Magnetic Field,HMF) forms a link between the magnetic flux at the top of the solar atmosphere(open magnetic flux, OMF) and the Earths environment (Owens and Forsyth,2013; Lockwood, 2013). This connection can be distorted temporally mainly bytwo agents, giving rise to auroras, among other effects.

i) Coronal mass ejections, CME: They are transient phenomena linked tolarge-scale reorganizations, reconnection, of the magnetic field in closed configu-rations (active regions). They consist of a massive burst of solar ionized particles


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Figure 3. Histograms (independently normalized) of geographic latitudes for Europe, NorthAmerica, and Asia using the different catalogues.

threaded with magnetic field lines, ejected from the Sun over the course of a fewhours. The CME rate closely follows the solar cycle, expressed by the sunspotnumber (Webb and Howard, 1994; Robbrecht, Berghmans and Van der Linden,2009) and the Gnevyshev double peak (Gnevyshev, 1967; Feminella and Storini,1997), but the main physical parameters of CMEs lag the sunspot number by12 years (Gonzalez et al., 1990; Du, 2012).

ii) High-speed streams: Large-scale magnetic regions in the solar atmospherehave field lines open outwards to the interplanetary medium, the so-called coro-nal holes (CH). Long-lived coronal holes are sources of high-speed streans in thesolar wind, and are related to recurrent geomagnetic activity (Krieger, Timothyand Roelof, 1973). Low-latitude CHs occur more frequently in the decliningphase of the sunspot cycle (Verbanac et al., 2011).

Figure 4 shows the temporal variation of estimates of the sunspot number(Clette et al., 2014) and open magnetic field (Solanki, Schussler and Fligge,2000). Usoskin et al. (2002) carried out simulations of the variations of the OMFwith a model based on the emergence and decay rates of active regions (Solanki,Schussler, and Fligge, 2002). That model fits other proxies of solar activity, suchas the 10Be records in ice cores, reasonably well. There is a clear maximum at


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the beginning of 17th century, followed by the Maunder Minimum (no yearlydata are available; see however Owens, Usoskin and Lockwood, 2012), and therapid increase in the 18th century (Alanko-Huotari et al., 2007). This behaviourwill be studied in the next section in detail with our auroral observations.

Figure 4. Temporal variation of the open magnetic field (solid lines) and the Sunspot Number(courtesy: M. Schussler). The Sunspot Number values before the Maunder Minimum are fromUsoskin, Mursula and Kovaltsov (2003) and Vaquero et al. (2011).

Siscoe (1980) discriminated between auroras that are visible north and southof 54 degrees using Scandinavian records, noting that the southern data trackedthe 11-year solar cycle more clearly. The Greenland observations confirmed that,at high latitudes, the aurora maximum coincides with the sunspot cycle min-imum7, and confirmed in many later publications. Bravo and Otaola (1990)studied the location of solar coronal holes and their influence on the auroralrecords. They found that the number of auroras is positively correlated withpolar coronal holes that reach solar latitudes below 60 degrees. Verbanac et al.(2011) found that high-speed streams originating in equatorial coronal holes arethe main driver of geomagnetic activity in the declining phase of the solar cycle.

In order to differentiate between the distinct solar sources, we plotted thecumulative values, NLat,j, of the number of auroras visible for each 1.5 degreewide latitude band. These values were computed using the formula

NLat,i =

nLat,j. (1)

The increase found is almost exponential. We took the resulting curve toconsist of three segments, to each of which we made straight-line fits. The inter-section of the three segments could represent the boundaries between differentsolar sources of the auroral event. The three pairs of plots of Figure 5 show theresults for Europe, North America, and Asia, respectively.

7This is based on calculations made by S. Tromholt analysing the observations made inGreenland by M. Kleinsmidt at Godthaab (cited in Lemstrom, 1886, pp. 40-41).


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The low-latitude segment would represent the auroras produced by strongsolar storms, with the northern limit at 49 degrees in Europe and 39 degreesin North America. This would define the so-called low-latitude auroras. Themiddle segment corresponds to auroral events produced by CMEs of mediumstrength. In the upper latitude segment, the predominant role is played by thefast streams from coronal holes. In this case, the variation of the geographiclatitude plays only a minor role. The limits are approximately 66 degrees forEurope and 44 degrees for North America. One must take into account thathigh-latitude auroras also occur when CMEs hit the Earth during an episode ofnorthward polarity of the IMF (Cumnock, 2005; Cumnock et al., 2009).

Figure 5. Cumulative values of the number of auroras visible per 1.5 degrees latitude bin (seethe text for explanation). Top panel: Europe and North Africa. Middle panel: North America.Bottom panel: Asia. The panels on the right are plots on a logarithmic scale.

The latitude distribution is flat-topped at high latitudes (low activity) andwith a linear decrease towards low-latitude auroras (high activity). Hapgood(2011) reported a similar behaviour for the occurrence frequency of the ge-omagnetic index aa, typical of a power-law distribution. A parabolic shape


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gives a suitable fit to the data, with most of the shoulder being avoided inthe calculation:

logN = (6.0 0.3) + (0.29 0.01) (0.0019 0.0001)2 EUROPE (2)

logN = (8.6 1.1) + (0.48 0.05) (0.004 0.0006)2 NORTHAMERICA(3)

logN = (0.9 0.5) + (0.10 0.02) (0.0007 0.0002)2 ASIA (4)

where is the geographic latitude in degrees.

4. Temporal Variation

The 11-yr cycle was the first hint of solar variability of magnetic origin (Schwabe,1844). There followed the suggestion that longer cycles might exist (Gleissberg,1939, 1944, 1967) with quasi-periodicities in the range 80120 years.

In the present study, we are mainly interested in time scales longer than the11-yr solar cycle. The existence of variability of the solar activity at these scales(1001000 yr) has been interpreted in terms of chaotic fluctuations of the solardynamo, and is identified as a phase catastrophe of the 11-yr cycle in the records(Kremliovsky, 1994; Choudhuri and Karak, 2012; Pipin, 2014).

Different proxies have been used to study the past solar activity. The SunspotNumber has clearly been the most often used. Another is based on the anti-correlation of solar activity with the galactic cosmic ray flux, and thus with theabundance of cosmogenic isotopes stored in different terrestrial reservoirs. Forreviews concerning the long-term variation of solar activity, see Usoskin (2013).

Using different proxies, Peristykh and Damon (2003) and Ma (2009) havefound a persistence of the Gleissberg cycle over 7000 and 12 000 years, re-spectively. Usoskin et al. (2004) have reconstructed the Sunspot Number from10Be records, finding a 600 yr periodicity together with the Gleissberg cycle.Hanslmeier et al. (2013) found that various solar proxies are affected by differentnon-solar factors, and reflect only the solar activity at long-term scales (> 80yr). Following estimations of cosmic ray intensities based on 10Be measurements,McCracken et al. (2013a) suggested the existence of great stability in the Gleiss-berg cycles (87 yr and multiples). In a later paper (McCracken et al., 2013b),they determined the timing of 26 Grand Minima with an average duration of50-100 years (see also Usoskin, Solanki and Kovaltsov, 2007).

The following are some of the recent findings that particularly stand out.McCracken (2007) shows that the level of the HMF has increased from 1500 tothe onset of the present century, with maxima occurring in 1735, 1780, 1850,and 1950. Based on nitrate concentrations measured in ice cores, McCracken etal. (2001) indicate the existence of well-defined maxima of solar proton events


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reaching the Earth for the years 1610, 1710, 1790, 1870, and 1950. And Traversiet al. (2012) detected Gleissberg cycles in their measurements of nitrate contentsin an Antarctic ice core to study the solar variability during the Holocene, thusproviding an independent test of their long-term existence. However, this resulthas been disputed by several authors (Wolff et al., 2012; Duderstadt et al.,2014), who showed that nitrate cannot be a reliable tracer of solar energeticparticle (SEP) events. On the other hand, Traversi et al. (2012) have indicatedthat the use of nitrate is useful to trace the variability of Galactic Cosmic Rays(GCR), detecting Gleissberg cycles in their measurements of nitrate contentsin an Antarctic ice core and studying the solar variability during the Holocene.Therefore, they provide an independent test of their long-term existence.

The solar equatorial rotation rate and its latitude variation are related to thelevel of magnetic activity (Balthasar, Vazquez, Wohl, 1986; Casas, Vaquero andVazquez, 2006). For past times, it has been determined from sunspot drawingsmade in different epochs. Javaraiah, Bertello and Ulrich (2005) have detectedchanges in the latitudinal rotation gradient with a periodicity close to 80 years,similar to the length of a Gleissberg cycle. Mouradian (2013) has suggestedthat the sunspot rotation rates show a 54.7 yr periodicity, putting forward theview that this should be the parameter that defines a long-term cycle, with theGleissberg cycle being just a harmonic (109.4 years).

The analysis of different auroral catalogues shows a quasi-80-year periodicity the Gleissberg cycle (Hansteen, 1831; Siscoe, 1980; Feynman and Fougere,1984). Feynman and Ruzmaikin (2014) confirm that the extremes of the au-roral distribution are consistent with a Gleissberg cycle, also reflected in theSunspot Number but differing in phase. Riley (2012) has studied the problemfrom another perspective, estimating that a Carrington-like event has a 10 per-cent chance to occur in a decade, and implying a 100-yr periodicity in the lowlatitude records. Yermolaev et al. (2013) suggests that a Carrington-1859 stormis observed only once every 500 years.

Figure 6 gives an overview of the temporal and latitudinal variation of theauroral observations recorded in our sample. Additional information is providedby Figure 7 with plots of the yearly number of auroras in our catalogue. Bothfigures reflect the population effects commented on in previous sections. However,our main interest lies in the long-term variation of solar activity, and for thispurpose we divide our sample into the seven subperiods discussed in the followingsubsections.

4.1. The Maunder Minimum (1645-1715)

Some decades after the discovery of the 11-yr cycle in sunspot records (Schwabe,1844), Sporer (1889) and Maunder (1894) reported the existence of a period inthe second half of the 17th century when sunspot activity was markedly reduced the Maunder Minimum (hereafter, MM). Eighty years later, in a seminal paper,Eddy (1976) revived the topic, bringing new proofs and associating the episodewith the Little Ice Age.

Gleissberg, Dambolt and Schove (1979), Schroder (1988), and Schlamminger(1990) reported auroral observations which confirmed that the heliosphere during


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Figure 6. Temporal and latitudinal variation of aurora borealis events visible during the lastfour centuries as reported in different archives (see Table 2) in (top) Europe and North Africa,(middle) North America, and (bottom) Asia.

this period presented the 11-yr periodicity. The same behaviour was found by

Nesme-Ribes and Ribes (1993) based on sunspot observations for 1660-1719,

although they detected a strong north-south asymmetry in the sunspot loca-

tions (see also Vaquero, Nogales and Sanchez-Bajo, 2015). Other studies have

discussed the 11-yr period during the MM (Beer, Tobias andWeis, 1998; Usoskin,

Mursula and Kovaltsov, 2001). Recently, Vaquero et al. (2015) have proposed

that the solar cycle was shorter during the MM (approximately 9 years).


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Figure 7. Annual aurora borealis number.

Auroral events occurred during this period when no sunspots were presenton the solar disk (Leftus, 2000). Owens and Lockwood (2012) calculated thatthe CME rate during this episode was similar to that of the two recent solarminima. More recently, Zolotova and Ponyavin (2015) proposed on the basis ofsunspot data that the MM seems to be an ordinary Gleissberg Minimum with adepressed 11-yr periodicity. This was contested however by Usoskin et al. (2015)arguing that solar activity during the MM was very low, although the exact levelis still unclear.

The presence of a strong red flash during two eclipses in 1706 and 1715 thatoccurred in the MM would require a substantially high solar magnetic fieldstrength (Foukal and Eddy, 2007). Riley et al. (2015) used a magnetohydro-dynamics model with the pertinent observational constraints, finding that theconfiguration of the corona at the recovery after the deep Maunder minimumwas not typical of Schwabe or Gleissberg Minima. In an analysis of sunspotdrawings, Casas, Vaquero and Vazquez (2006) found an anomaly in the solarrotation during the deep MM compared to determinations made before andafter this episode.

According to Sokoloff (2004), the transition to the deep minimum was abrupt,while the end was fairly gradual. However, Vaquero et al. (2011) revised thesunspot numbers around 1640 and found that the transition to the deep mini-mum was also gradual. For the period before the MM, Leftus (2000) found thatthere were peaks in the sunspot number in 1614, 1624, and 1639 (see Figure 4).A recent analysis of historical sunspot data by Vaquero et al. (2015) indicates


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the existence of sunspot number peaks also in the deep minimum, namely in16551657, possibly 1666, 1675, 1684, and 1705. In the auroral records of thepresent study (Figure 8), one can see relatively strong activity in the first decadesof the 17th century, followed by the Maunder episode which presents a 20-yearquasi-periodicity until its end, similar to the dominant cycle that Usoskin et al.(2001) found with clusters of sunspot occurrences.

Figure 8. Annual aurora borealis numbers during the 17th century in our records. Europeand North America (dashed line) and the total of Europe, North America, and Asia (solidline).

The lack of auroras visible at high and low latitudes in our data, does notallow any clear statement to be made about the consideration of the MM as aGrand Minimum or just a Gleissberg Minimum. In this context, the Asian dataare essential, but, as will be seen below, they are still highly controversial withregard to their reliability.

4.2. The 18th century rise in solar activity (1715-1800)

4.2.1. The rise in solar activity

After the MM, with the clear rise in solar activity, the works of Halley (1716)and Mairan (1733) marked the beginning of modern studies of auroras, in whichthere was a dramatic increase in the number of aurora reports.

The middle panel of Figure 6 reflects the paucity of North American dataduring the 18th century, especially at high latitudes. As the settlement of thewestern regions progressed, there was a concomitant increase in the number ofreports. The New England records are, however, relatively frequent over the


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whole period. The bottom panel of that figure reflects how few data we wereable to find for auroral observations in Asia.

The strongest auroral event during this interval occurred on 18 January 1770(Vazquez, Vaquero and Curto, 2006; Schroder, 2010). It was visible in NorthAfrica. Also remarkable in the same year were the events of 16-18 September(Willis and Stephenson, 1996), observed in China and Japan and also visible atlow latitudes in Europe (Vazquez and Vaquero, 2010).

4.2.2. The lost cycle

A 15-yr cycle (Schwabe Cycle Number 4) took place at the end of this periodof rise in solar activity (1790 approximately). Usoskin, Mursula and Kovaltsov(2001) proposed that in fact there existed two cycles in this period. Later,Usoskin et al. (2009) constructed butterfly diagrams for the period, finding thathigh-latitude sunspots were present in 1793, an indicator of the start of a newcycle. A recent Bayesian analysis of 10Be records (Karoff et al., 2015) seems tosupport this hypothesis. Our records (Figure 9) show first the standard Cycle4 and then an extended decay tail with a hint of a secondary maximum (seealso the records of Krivsky and Pejml, 1988, and Legrand and Simon, 1987).However, it is still unclear whether it was a new cycle or just a burst of activity(Zolotova and Ponyavin, 2011).

Other factors could also have played a role in the decrease of observations.For example, the eruption of the Laki volcano in Iceland (17831784) emittedmuch dust into the European (Thordarson and Self, 2003) and South American(Trigo, Vaquero and Stothers, 2010) skies.

4.3. The Dalton Minimum (17901830)

Named after John Dalton (17661844) who kept a meteorological journal for 57years, including aurora borealis observations (Dalton, 1873), the Dalton Min-imum in sunspot numbers also corresponded to a reduction in the numberof auroras observed (Silverman, 1992; Broughton, 2002; Vaquero, Gallego andGarcia, 2003), as is clearly confirmed in our European data. (We remedied thelack of high-latitude records in the Fritz catalogue by including the Scandinavianobservations of Tromholt and Rubenson.) The auroras observed in Barcelona in1811 and 1812 are remarkable, and call for detailed confirmation.

4.4. The new 19th century rise in solar activity

The 19th century period of a rise in solar activity is full of strong auroralevents, including the famous Carrington aurora (1859, 28 August and 2 Septem-ber), a paradigm of solar-terrestrial relationships (Kimpball, 1960; Cliver andSvalgaard, 2004; Silverman, 2006; Cliver and Dietrich, 2013). Some years later,there occurred the events of 24 January 1870 and 4 February 1872 (Silverman,2008). Taken together, these represent the highest peak of auroral activity inour sample.

Observations of high-latitude auroras were favoured by the organization ofthe first International Polar Year campaign (from 1881 to 1884), producing


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Figure 9. Annual aurora borealis number at the end of the 18th century in Europe and NorthAfrica.

an accumulation of recorded high-latitude events that is visible in our plots.See Raspopov, Kuzmin, and Kharin (2007) and Barr and Ludecke (2010) fordescriptions of the various International Years that are related in some way withauroral observations.

Uberoi (2011) reports an auroral observation of the 1872 event in Aden, at12 degrees north geographic latitude8. That this would imply a geomagneticlatitude of only 2 degrees raises severe doubts about the observations reliability.We have therefore excluded it from our records9.

4.5. The Gleissberg Minimum of solar activity (18801910)

At around the turn of the 19th to the 20th century, the level of auroral activityagain decreased, a fact that has already been remarked on in previous studies.The records of the geomagnetic index aa show a clear minimum at around 1901.Brown (1976) detected a minimum of the Gleissberg cycle at the end of Cycle13, around 1902.

Since Solar Cycle 14 (1902 1913), the geomagnetic activity has lagged behindthe sunspot number, but before that date the lag seems to have been less notable(Love, 2011). Lockwood and Owens (2014) found that, during the minima of

8Published in the Times of India with the remark The aurora was brilliant in the extreme.9The same attitude was taken to an observation of the 1859 event at St George of Mina (nowin Ghana) at 5 degrees north geographic latitude, contained in the Fritz catalogue.


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11-year Schwabe cycles at around 1879 and 1901, the average solar wind wasexceptionally low, implying that the Earth remained within the streamer belt ofslow solar wind flow for extended periods.

Balthasar, Vazquez and Wohl (1986) in analysing sunspot records detected adecline in the solar rotation in around 1902 between Schwabe Cycles 13 and 14,bringing to mind the recent proposal by Mouradian (2013) of the importance ofthis parameter for the long-term behaviour of the solar dynamo.

4.6. The 20th century

Particularly remarkable is the marked drop in the quantity of data for the period1960-1980 in all three samples. An explanation could be the changing way thattheories about auroras were developed. For many centuries, auroras were mainlyregarded as an atmospheric phenomenon, with reports by laymen being laterincorporated into the meteorological record. There was a gradual growth ofawareness of their connection with solar activity and geomagnetic perturbations(Maunder, 1905). Routine observations were abandoned, and interest in themshifted to geophysicists studying the physics of isolated events (Legrand andSimon, 1987). Odenwald (2007) studied the yearly number of aurora reportsappearing in newspapers. He found a sharp reduction after 1960, probably aresult of the coming of the space age and the popularization of television.Nonetheless, this effect was partially compensated by the various auroral obser-vation campaigns organized in the framework of the International GeophysicalYear (IGY). These campaigns mostly affected the period 19571960, and theyhad a certain clear bias towards high-latitude sites10.

In the 1990s the diffusion of digital images over the Internet led to a newincrease in observations. Moreover, all-sky imaging programs were started, suchas those corresponding the GAIA and THEMIS consortia (Mende et al., 2008).In order to allow a certain normalization with older data, we have taken especialcare to select only strong events so as to make the digital images comparablewith the photographic and visual observations of the past.

The start of this period is marked by the strong auroral events of 25 September1909 (Silverman, 1995) and 14-15 May 1921 (Silverman and Cliver, 2001). Alater outstanding event is that of 25 January 1938 which was widely reportedin the press (Barlow, 1938). Also remarkable is the strong activity of Cycle 19,peaking as the maximum of a long-term cycle in 1957, just at the start of theaforementioned IGY campaigns,

The CME of 4 August 1972 also merits particular comment because it hadthe appropriate parameters for it to become a superstorm similar to that of theCarrington 1859 event (see Gonzalez et al., 2011, for references), but in auroralrecords of our catalogue it was only visible as a moderate event. The polarityof the IMF was directed northwards, thus avoiding a massive input of particlestowards low-latitude sites. This is a good illustration of why many parametersmust combine to produce a super-event.

10These data are stored at the World Scientific Center for Aurora, Japan.


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The aurora of 13 March 1989 (Shirochkov et al., 2015) marked an inflectionpoint in public interest in space weather studies and their technological influ-ences. The well-known blackout of Quebec and nearby areas has been studied indetail (Boteler, 2001; Hapgood, 2011) and popularised in the press.

More recently, in Schwabe Cycle 23, there occurred the so-called Halloweenperiod of strong solar activity, with two phases of activity in October and Novem-ber of 2003 (Kane, 2005). The first phase was concentrated in the days between19 October and 12 November. Spacecraft as distant as Ulysses, Cassini andVoyager 2, were able to detect the enhancements of solar particles, correspondingto distinct CMEs, at different heliocentric distances (Burlaga et al., 2005; Larioet al., 2005). In the second phase, an event on 20 November was associated with alarge geomagnetic storm (Karavaev et al., 2009) produced by a halo CME. Whatmade this event special, however, was the high IMF and its strong southwardcomponent (Gopalswamy et al., 2005; Srivastava et al., 2009). The duration ofthe solar windmagnetosphere interaction was very long 13 hours (Srivastava,2005). The corresponding aurora was observed at very low latitudes (Vazquezand Vaquero, 2010). For mid-latitude observations in Asia see Mikhalev et al.(2004).

4.7. The recent minimum (20062009)

The last minimum of solar activity, between Cycles 23 and 24, has attracted theattention of solar astronomers due to its extended duration and the low valuesof solar irradiance measured during this interval (Frohlich, 2013) .

According to McCracken and Beer (2014), the measured levels of cosmic raysare incompatible with the existence of a Grand Minimum in the present times.Rather, they reflect a minimum of the Gleissberg cycle. Echer, Tsurutani andGonzalez (2011) showed that the low levels of solar and geomagnetic activityare similar to the previous Gleissberg minimum at the beginning of the 20thcentury.

The present Cycle 24 is characterized by a small amplitude, typical of theextended phase of a Gleissberg Minimum. However, strong auroral events couldyet occur in this cycle. Indeed, the weak sunspot activity for Cycle 24 is not seenin the CME occurrence of the same period (Jian, Russell and Luhmann, 2011).Gibson et al. (2011) remark that during this episode the Earth was periodicallyimpacted by high-speed streams originating from long-lived coronal holes, whichsuggests an unusual configuration of the large-scale solar magnetic field, at leastcompared with the previous cycle. Based on an analysis of nitrate records in icecores, Barnard et al. (2012) suggest that a return to low levels of solar activitywill indeed lead to a decrease in the auroral frequency, but also to an increase inthe average fluence per auroral event. This calls to mind the sporadic low-latitudeauroras occurring in relatively quiet periods.

Helioseismic measurements with different ground- and space-based instru-ments (Broomhall et al., 2009; Salabert et al., 2011; Jain, Tripathy and Hill,2011) indicate changes in the frequencies of acoustic p-modes during the ex-tended minimum, interpreted as changes in the magnetic field deep in the con-vection zone, including a possible role for a deep-seated relic magnetic field inthe solar interior.


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Auroral records of our catalogue show some features typical of a GleissbergMinimum. However, it would be premature to reach any conclusion in thisrespect given the duration of these episodes. One needs to wait and continueobserving, keeping in mind that the geomagnetic effects of solar activity usuallylag the sunspot number.

In summary, our sample can be divided into four long-term Gleissberg cycles.We cannot conclude whether or not the MM corresponds to one of them due tothe scarcity of low-latitude auroras in the first part of the 17th century. Figure10 plots the values of the annual minimum latitudes for the auroral events forEurope and North Africa regions with a better observational coverage.

Figure 10. Annual values of the minimum geographic latitudes of auroral events for Europeand North Africa (solid lines) and North America (dashed lines).

5. The Geomagnetic Latitude

Since the frequency of auroras is related to distance from the magnetic pole, itis more appropriate to plot the observations vs. magnetic latitude.

5.1. Model of the geomagnetic field

We computed the temporal evolution of the geomagnetic latitude for every ob-serving location during the entire period of our study. It is common to definewithin the main geomagnetic field the geomagnetic latitude according to the


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expression tan = (tan I)/2 (see Buforn, Pro, and Udas, 2012). We obtained

the magnetic inclination (I) from the global geomagnetic model gufm1 (Jackson,

Jonkers, and Walker, 2000). This model is based on observational data of the

intensity of the geomagnetic field during the last centuries. The validity of this

model for the last four centuries has been verified by Pavon-Carrasco et al. (2014)

by comparison with archaeomagnetic data.

As an example, Figure 11 represents the pairs of geomagnetic and geographic

latitudes for all the available data. In the plots, we have differentiated the results

calculated with the well-known IGRF (International Geomagnetic Reference

Field) model, valid for the period from 1900 to the present (De Santis, 2007).

Figure 11. Plots of geographic vs. geomagnetic latitudes for all the available data, subdividedinto the three subsamples. Black asterisks: gufm1 model (1600-1989). Red asterisks: the IGRFmodel (1989-2015).


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5.2. Latitude variation

Figure 12 shows the results of the geomagnetic latitude of auroral occurrence forEurope, North America, and Asia. One observes the Dalton Minimum betweenthe two high-activity episodes. However, the low geomagnetic latitudes duringthe 18th century are mainly covered by Asian data. Two episodes with high-latitude auroras occur in 1820 and 1840 close to the minimum phase of thecorresponding solar cycles. An unusual aurora was visible close to the geomag-netic North Pole (Fort Conger) on 17 November 1882. These observations weremade by the expedition commanded by A.W. Greeley from July 1882 to August1883 in the framework of the activities of the First Polar Year (Taylor, 1981).In this context, Singh et al. (2012) have recently studied the characteristics ofhigh-latitude storms above the classical auroral oval.

Figure 12. Temporal and geomagnetic latitude distribution of the auroral event observations:(black diamonds) Europe and North Africa; (red squares) North America; (red triangles) Asia.

Figure 13 shows the histograms of the geomagnetic latitudes for the threecontinental areas. There stands out the major contribution of the otherwisesparse Asian data to the low geomagnetic latitudes. These observations mainlycorrespond to a group of exceptionally strong aurora events occurring aroundthe maximum of one of the strongest cycles of the 19th century, 1872 (see Figure8).

We repeated the calculation of the cumulative number of auroral events, butnow for the geomagnetic latitudes. The results (Figure 14) show the behaviour tobe similar for the two continents of Europe plus North Africa and North America,although there are relatively few high geomagnetic latitude observations in theNorth American sample (Canada and Alaska). Liritzis and Petropoulos (1987)


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Figure 13. Histogram of the geomagnetic latitudes. (Top) Europe and North Africa; (middle)North America; (bottom) Asia.

already noted that there is a marked change at a geomagnetic latitude of 57 58 degrees. Although there are too few Asian data to be significant, they areincluded for the sake of comparison, especially in the low-latitude range.

As with the geographic latitudes, we fitted parabolas to the three subsamples.For Europe, the results were practically identical to those for the geographiclatitudes. They differed slightly for North America. We excluded the Asian datadue to the relatively smaller number of observations.

logN = (4.6 0.7) + (0.23 0.03)mag (0.0013 0.0003)2mag Europe (5)

logN = (3.1 1.1) + (0.16 0.02)mag (0.0007 0.0002)2mag NorthAmerica

(6)where mag is the geomagnetic latitude.

5.3. The Gleissberg cycles

Schove (1955) was probably the first to date the extremes of the last Gleiss-berg cycles, confirming the existence of a 78-yr periodicity at least since 200BCE. Feynman and Silverman (1980), using only records from Sweden and NewEngland, also detected low values of auroral activity during the different Gleiss-berg Minima. Garcia and Mouradian (1998) calculated the maxima and minimaof Gleissberg cycles after 1750 using sunspot records, and following the samemethod as Gleissberg (1960). They were able to study a complete Gleissberg


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Figure 14. Cumulative values of the number of auroras below a certain minimum geomagneticlatitude. () European and N. African sample; () North American sample; () Asian data.Left panel: normal scale. Right panel: logarithmic scale.

cycle (from the Dalton Minimum to the 20th century Minimum), the decay ofthe previous cycle, and the peak of the present cycle with the maximum ataround 1957.

Figure 15 shows the annual variation of the minimum latitude reached byauroral events. The Gleissberg cycle also presents a double peak. The dates ofthe secondary maxima have been studied by Hoyt and Schatten (1997). Gonzalezet al. (2011) suggested that extreme events can be expected to occur at the rateof about one per century, with a tendency to appear close to the secondarymaximum in the descending phase of the Gleissberg cycle. Table 7 summarizesthe main parameters of these cycles based on our records. We could also haveincluded a Gleissberg Cycle number 0, elapsing from the Sporer Minimum (year1570) to the MM, but the auroral data are very limited both spatially andtemporally.

In principle, one might explain the 1848-1872 interval as the maximum of anapproximately 200-year cycle (so-called Suess cycle) of auroral activity (Suess,1980). Silverman (1995) set a minimum geomagnetic latitude of 15 degrees atwhich auroras can be observed. This is surpassed by the observations during thissupermaximum.

Ogurtsov et al. (2002) studied two proxies of solar activity sunspot numberand cosmogenic isotopes and found that the Gleissberg cycle has a frequencyband with a double structure consisting of periods of 5080 yr and 90140 yr,whereas the Suess (or de Vries) cycle only presents one period of approximately210 yr.


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Figure 15. Annual variation of the minimum geomagnetic latitude of auroral events. Solidline, absolute minimum values for North America and Europe plus North Africa. Triangles,values for Asia.

Table 7. Overall characteristics of the four Gleissberg cycles (GC) in our sample. The datesare taken from Gonzalez et al (2011). SMAX stands for secondary maximum and GMLminfor the minimum value of the geomagnetic latitude during the corresponding period. SNMAxindicates the maximum value of the annual sunspot number, and N is the number of aurorasin the corresponding Gleissberg cycle for Europe and North Africa.

GC Start Maximum SMAX End GMLmin (time) SNMax (time) N

I 1700 1770 1809 15 154.4 (1778) 8516

II 1810 1839 1870 1909 8 (1859) 139.0 (1870) 13 765

III 1910 1958 1980 2009 18 190.2 (1957) 15 085

IV 2009 34 ..

Figure 16 displays variations of the cumulative numbers of auroras as a func-tion of geographic and geomagnetic latitude of three Gleissberg cycles. Due tothe different amounts of data available in each cycle, we have normalized thenumber N of auroras to the maximum value of each cycle.

6. Conclusions

We have presented here the first analysis of a catalogue that aims to summarizemost of the available visual aurora borealis observations from 1600 to the presentday. To this end, latitudes were assigned to more than 160000 auroral observa-tions. For the analysis, we divided the Northern Hemisphere into three large


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Figure 16. Global Variation with the geographic (upper plot) and geomagnetic (bottomplot) latitudes of the cumulative number of auroras for the Gleissberg Cycles I (solid lines), II(dashed lines), and III (dashed-dotted lines). Data: Europe and North Africa.

continental areas corresponding to Europe (plus North Africa), North America,

and Asia. The sample had numerous spatial and temporal gaps. This was par-

ticularly evident in the North American data due to the progressive European

occupation of large areas beyond the original New England states.

There are some evident gaps in our catalogue. We have commented on them

throughout this communication. The gaps correspondmainly to high and low lat-

itudes in North America for the 17th and 18th centuries, and to many practically

uninhabited places in Asia.

Trying to fill these gaps would therefore be unlikely, apart from finding and

adding some isolated data. In this respect, one can say in synthesis that the

spatial and temporal distribution of auroral observation data is affected at least

as much by the population effect as by the purely geomagnetic effect.

We re-applied a method developed in Vazquez, Vaquero and Gallego (2014)

to separate the contribution of the different solar sources of auroral events. It is

based on the different slopes of the cumulative numbers of auroral events per lat-

itude bin. The low-latitude segment mainly corresponded to strong CMEs taking

place around the solar cycle maxima. The mid-latitude segment corresponded to

standard CMEs, and the high-latitude segment to high-speed streams of solar

wind originating from coronal holes. The limit between these last two sources

lies in a narrow belt between 64 and 67 degrees geomagnetic latitude. One must

bear in mind that the geoeffectiveness of such transitory solar events depends


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critically on the level of the IMF and its orientation with respect to the Earthsmagnetosphere.

The three subsamples of our catalogue presented the same trend in the cu-mulative number of auroral events vs. geomagnetic latitude. Only a few eventsdeviated from this behaviour. They corresponded to Gleissberg cycle maxima.

As indicated above, the spatial distribution of the available data is clearlydetermined by the populations living at high-latitude sites. These populationswere clearly greater in Europe than in North America. The same may apply tothe low-latitude sites in the two continents. The result may have been to maskthe expected better correlation of the auroral parameters with the geomagneticthan with the geographic latitude.

Apart from the population effect, the occurrence of specific auroral events ofgreat strength is driven by chance (see the different cases discussed in Section 4),but with a notable dependence on the amplitude of the corresponding 11-yr cycle.However, the long-term behaviour of the auroral activity is clearly driven by adeterministic process (whether chaotic or not), and particularly by the phaseof the Gleissberg cycle. In other words, there are some short extreme eventsinserted into a slowly varying background, and these events are attributable tohigh-speed streams from coronal holes. The geomagnetic component due to theslow solar wind (see Legrand and Simon, 1987, for a classification) is not reflectedin our sample, because any auroras it might produce are very faint.

The observations of low-latitude auroras in Asia are very puzzling. They canbe divided into two groups. First , there are the MM observations at relativelylow geomagnetic latitudes (Willis and Stephenson, 2000). Zhang (1985) notedthat 23 times more auroral observations were reported in Korea during the 1507-1749 period than in China. The author proposed that they were Stable AuroralRed Arcs, visible at the edge of the auroral oval, although Kozyra, Nagy andSlater (1997) argue to the contrary. Nonetheless, by itself, this assumption cannotexplain the southward extension of the Korean observations, especially duringthe MM. More recently, Willis and Davis (2015) have presented new evidence forrecurrent auroral activity in 1625 and 1626, a time prior to the MM, evidencethat is fully compatible with other activity indicators (see Figure 4). Whateverthe case, the very low latitude observations in India and Arabia for the 1872super-event are well documented. A possible factor to consider is the geomagneticmodel we have been using because it is at the edge of its range of reliability forthe 17th century. Even so, any errors that result cannot be so large. Willis andStephenson (2000) give a range of geomagnetic latitudes for Asia of 25-38 degrees,similar to our determinations. In this regard, those same authors (Willis andStephenson, 2002) report that the Korean observations during the 17th centurywere seen in a southerly direction. Oguti and Egeland (1995) commented that,given its low geomagnetic latitude, Korea should not have seen auroral activityin the last 1000 years. Second , there are observations at very low geomagneticlatitudes during the 19th century super-events, visible as a separate group inthe overall histogram. In this case, however, the observations seem to be veryreliable.

The aim with this first communication using the whole catalogue has been topresent the long-term characteristics of the last Gleissberg cycles really crucial


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to understanding the space climate. It will be followed by others analysing indetail the spatial and temporal oscillatory patterns, and the potential of suchanalyses to contribute to the reconstruction of past heliospheric activity.

Finally, we would like to invite readers to contact the authors in a casethat they have information on auroral observations at sites and/or at timesnot included in this paper. The complete catalogue is still in progress and willbe stored in a World Data Center at the end of the project, including alsodata of aurora australis. Colleagues interested in this preliminary version of ourcatalogue are invited to contact the lead author.

Acknowledgements The authors wish to express their gratitude to Sam Silverman whoundertook the immense task of collecting thousands of auroral reports around the world andmaking them available to the scientific community. Some well-known auroral catalogues (Fritz,Angot) used for this study are from Jack Eddys Compilation of Auroral Catalogues and wereobtained from the Research Data Archive (RDA), which is maintained by the Computationaland Information Systems Laboratory (CISL) at the National Center for Atmospheric Research(NCAR). NCAR is sponsored by the National Science Foundation (NSF). The original dataare available from the RDA (dss.ucar.edu) with dataset number ds836.0. The following personsprovided information and/or data of auroral events: A. Kadokura (WDCA, Japan), M. Connors(GAIA program, Canada), and K. Erhardi (DMI, Denmark). Support from the Junta de Ex-tremadura (Research Group Grants) and from the Ministerio de Economia y Competitividad ofthe Spanish Government (AYA2011-25945 and AYA2014-57556-P) is gratefully acknowledged.

References

Akasofu, S.I.: 2015, History of Geo and Space Sciences 6, 23.Alanko-Huotari, K., Usoskin, I.G., Mursula, K., Kovaltsov, G.A.: 2007, J. Geophys. Res. 112,

A08101.Angot, A.: 1897, The Aurora Borealis, D. Appleton & Co., New York (translation of the

original French version published in 1895).Aragones Valls, E., Orgaz Gargallo, J.: 2010, Treb. Mus. Geol. Barcelona 17, 45.Balthasar, H., Vazquez, M., Wohl, H.: 1986, Astron. Astrophys. 155, 87.Barlow, E.W.: 1938, Q. J. Royal Meteorol. Soc. 63, 215.Barnard, E.E.: 1902, Astrophys. J. 16, 135.Barnard, E.E.: 1909, Astrophys. J. 31, 208.Barnard, L., Lockwood, M., Owens, M.J., Davis, C.J., Hapgood, M.A., Steinhilber, F.: 2012,

EGU General Assembly, Vienna.Barr, S., Ludecke, C. (Eds): 2010, The History of the International Polar Years. Springer.Basurah, H.M.: 2004, Solar Phys. 225, 209.Beer, J., Tobias, S., Weiss, N.: 1998, Solar Phys. 181, 237.Bernard, F.: 1837, Am. J. Sci. Arts 34, 267.Brekke, P., Broms, F.: 2013, Northern Lights. A Guide, Forlaget Press.Bond, W.C., Bond, G.P., Winlock, J., Pickering, E.C.: 1889, Annals of Harvard College

Observatory 19, 50.Boteler, D.H.: 2001, Geophysical Monograph Series 125, pp.347352, P. Song, H.J. Singer,

G.L. Siscoe (eds), AGU Washington.Bravo, S., Otaola, J.A.: 1990, Ann. Geophysicae 8, 315.Broomhall, A.M., Chaplin, W.J., Elsworth, Y., Fletcher, S.T., New, R.: 2009, Astrophys. J.

700, L162.Broughton, P.: 2002, J. Geophys. Res. 107, 1152.Brown, G.M.: 1976, Mon. Not. Roy. Astron. Soc. 174, 185.Buforn, E., Pro, C., Udas, A.: 2012, Solved Problems in Geophysics, Cambridge University

Press, Cambridge.Burlaga, L.F., Ness, N.F., Stone, E.C., Mc Donald, F.B., Richardson, J.B.: 2005, Geophys.

Res. Lett. 32, L03S05.Casas, R., Vaquero, J.M., Vazquez, M.: 2006, Solar Phys. 234, 379.


Aurora Borealis

Chapman, S.: 1970, Annual Review of Astronomy and Astrophysics 8, 61.Choudhuri, A.R., Karak, B.: 2012, Phys. Rev. Lett. 109, 965.Clette, F., Svalgaard, L., Vaquero, J.M., Cliver, E.W.: 2014, Spa. Sci. Rev. 186, 35.Cliver, E.W., Dietrich, W.F.: 2013, Journal of Space Weather and Space Climate 3, A31.Cliver, E.W., Svalgaard, L.: 2004, Solar Phys. 224, 407.Cumnock, J.A.: 2005, J. Geophys. Res. 110, 2304.Cumnock, J.A., Blomberg, L.G., Kullen, A., Karlsson,T., Sundberg, K.A.T.: 2009, Ann.

Geophysicae 27, 3335.Dalton, J.: 1873, Meteorological Observations and Essays, London.De Santis, A.: 2007, Physics of the Earth and Planetary Interiors, 162, 217.Du, Z.: 2012, Solar Phys. 278, 203.Duderstadt, K.A., Dibb, J.E., Jackman, C.H., et al.: 2014, J. Geophys. Res. 119, 6938.Echer, E., Tsuratani, B.T., Gonzalez, W.D.: 2011, Extremely low geomagnetic activity during

the recent deep solar cycle minimum, in IAU Symposium 286, C.H. MAndrini and D.F.Webb (Eds), pp. 200-210.

Eddy, J.A.: 1976, Science 192, 1189.Feldstein, Y.I.: 1963, Geomag. Aeronomy 3, 183.Feldstein, Y.I., Vorobjev, V.G., Zverev, V.L., Forster, M.: 2014, History of Geo and Space

Sciences 5, 81.Feminella, F., Storini, M.: 1996, Cool Stars, Stellar Systems, and the Sun 109, 127.Feynman, J., Fougere, P.F.: 1984, J. Geophys. Res. 89, 3023.Feynman, J., Ruzmaikin, A.: 2014, J. Geophys. Res. 119, A8, 6027.Feynman, J., Silverman, S.: 1980, J. Geophys. Res. 85, A6, 299.Foukal, P., Eddy, J.A.: 2007, Solar Phys. 245, 247.Fritz, H.: 1873, Verzeichniss Beobachteter Polarlichter, C. Gerolds Sohn, Wien.Frohlich, C.: 2013, Spa. Sci. Rev. 176, 237.Garcia, A., Mouradian, Z.: 1998, Solar Phys. 180, 495.Gartlein, C.W., Moore, R.K.: 1951, J. Geophys. Res. 56, 85.Gibson, S.E., De Toma, G., Emery, B., Riley, P., Zhao, L.,Elsworth, Y.,Leamon, R.J.,Lei, J.,

McIntosh, S., Mewalt, R.A., Thompson, B.J., Webb, D.: 2011, Solar Phys. 274, 5.Gleissberg, W.: 1939, Observatory 62, 158.Gleissberg, W.: 1944, Terr. Mag. Atmos. Elec. 49, 243.Gleissberg, W.: 1960, Zeitschrift fur Astrophysik 49, 25.Gleissberg, W.: 1967, Solar Phys. 2, 231.Gleissberg, W., Dambolt, T., Schove, D.J.: 1979, Journal of the British Astronomical

Association 89, 440.Gnevyshev, M.N.: 1967, Solar Phys. 1, 107.Gonzalez, W.D., Echer, E., Clua de Gonzalez, A.L., Tsuratani, B.T., Lakhina, G.S.: 2011, J.

Atmos. Solar-Terr. Phys. 73, 1447.Gonzalez, W.D., Gonzalez, A.L.C., Tsurutani, B.T.: 1990, Planetary and Space Science 38,

181.Gopalswamy, N., Yashiro, S., Michalek, G., Xie, H., Lepping, R.P., Howard, R.A.: 2005,

Geophys. Res. Lett. 32, L12S09.Greeley: 1881, Chronological List of Auroras observed from 1870 to 1879, Prof. Pap. of the

Signal Service, Government Printing Office, Washington.Halley, E.: 1716, Phil. Trans. Roy. Soc. London 24, 406.Hanslmeier, A., Brajsa, R., Calogovic, J., Vrsnak, B.,Ruzdjak, D.,Steinhilber, F., Mac Leod,

C.L., Ivezic, Z.,Skokic, I.: 2013, Astron. Astrophys. 550, 2059.Hansteen, C.: 1831, Poggendorffs Annalen XXII, 536.Hapgood, M.A.: 2011, Adv. Spa. Res. 47, 2059.Harrison, G.: 2005, Astronomy and Geophysics 46(4), 31.Hoyt, D.V., Schatten, K.H.: 1997, The Role of the Sun in Climate Change, Oxford University

Press, Oxford.Jackson, A., Jonkers, A.R.T., Walker, M.R.: 2000, Phil. Trans. Roy. Soc. London A 358, 957.Jain, K., Tripathy, S.C.,Hill, F.: 2011, Astrophys. J. 739, 957.Javaraiah, K., Bertello, L., Ulrich, R.K.: 2005, Solar Phys. 232, 25.Jian, L.K., Russell, C.T., Luhmann, J.G.: 2011, Solar Phys. 274, 321.Kamide, Y., Maltsev, Y.: 2007, Geomagnectic Storms, in Handbook of the Solar Terrestrial

Environment, Springer Verlag, 355.Kane, R.P.: 2005, J. Geophys. Res. 110, A02213.


Vazquez et al.

Karavaev, Yu.A., Sapronova, L.A., Bazarzhapov, A.D., Saifudinova, T.I., Kuzminykh, Yu.V.:2009, Geomag. Aeron. 49, 961.

Karoff, C., Inceoglu,F., Knudsen, M.F.,Olsen, J., Fogtmann-Schultz, A.: 2015, Astron.Astrophys. 575, A77.

Kassner, C.: 1941, Meteor. Zeitschrift 58, 243.Kimpball, D.S.: 1960, Scientific Report No. 6, Geophysical Institute, University of Alaska.Kozyra, J.U., Nagy, A.F., Slater, D.W.: 1997, Rev. Geophys. 35, 155.Kremliovsky, M.N.: 1994, Solar Phys. 151, 351.Krieger, A.S., Timothy, A.F., Roelof, A.C.: 1973, Solar Phys. 29, 505.Krivsky, L., Pejml, K.: 1988, Publ. Astron. Inst. Czechosl. Acad. Sci. 84.Lario, D., Decker, R.B., Livi, S., Krimigis, S.M., Roelof, E.C.,Russell, C.T., Fry, C.D.: 2005,

J. Geophys. Res. 110, A09S11.Lassen, K., Laursen, O.R.: 1968, Danish Visual Aurora Observations, Danish Met. Inst.

Geophysical Papers.Lee, E.H., Ahn, Y.S., Yang, H.J.,Chen, K.Y.: 2004, Solar Phys. 224, 373.Leftus, V.: 2000, Solar Phys. 205, 189.Legrand, J.P., Simon, P.A.: 1987, Ann. Geophysicae 5, 161.Link, F.: 1964, Geofysikalmi Sbornik 212, 501.Liritzis, Y., Petropoulos, B.: 1987, Earth, Moon, and Planets 39, 75.Lisac, I., Marki, A.: 1998, Geofizica 15, 53.Livesey, R.L.: 1991, Journal of the British Astronomical Association 101, 233.Lockwood, M.: 2003, J. Geophys. Res. 108, 1128.Lockwood, M.: 2013, Living Rev. Solar Phys. 10, 4.Lockwood, M., Owens, M.J.: 2014, Astrophys. J. 781, L7.Loomis, E.: 1860, American J. Sci. 2nd Ser. 30, 79.Loomis, E.: 1861, Am. J. Sci. 2nd Ser. 32, 71.Love, J.J.: 2011, Ann. Geophysicae 29, 1365.Lovering, J.: 1866, Mem. A. Acad. Arts Sci. 10, 9.Lueders, F.G.T.: 1984, Publications Washburn Observatory 12, 20.Mairan, J.J.: 1733, Traite physique et historique de le Aurore Boreale, Paris, Impremerie

Royale.Ma, L.H.: 2009, New Astron. 14, 173.Maunder, E.W.: 1894, Knowledge 17, 173.Maunder, E.W.: 1905, Mon. Not. Roy. Astron. Soc. 65, 538.McCracken, K., Dreschhoff, G.A.M., Smart, D.F., Shea, M.A.: 2001, J. Geophys. Res. 106,

21599.McCracken, K.: 2007, J. Geophys. Res. 112, A09106.McCracken, K., Beer, J., Steinhilber, F., Abreu, J.: 2013a, Solar Phys. 286, 609.McCracken, K., Beer, J., Steinhilber, F., Abreu, J.: 2013b, Space Sci. Rev. 176, 59.McCracken, K., Beer, J.: 2014, J. Geophys. Res. 119, 2379.Mende, S.B., Harris, S.B., Frey, H.V., Angelopoulos, V., Russell, C.T., Donovan, E., Jacker,

B., Greffen, M., Peticola, L.M.: 2008, Spa. Sci. Rev. 141, 357.Mikhalev, A.V., Beletsky, A.B., Kostyleva, N.V., Chernigovskaya, M.A.: 2004, Cosmic Res.

42, 591.Milan, S.E., Hutchinson, J., Boakes, P.D., Hubert, B.: 2009, Ann. Geophys. 27, 2913.Milton, E.R.: 1962, J. R. Astron. Soc. Canada 56, 210.Milton, E.R.: 1969, J. R. Astron. Soc. Canada 63, 238.Moss, K., Stauning, P.: 2012, History of Geo- and Space Sciences 3, 53.Mouradian, Z.: 2013, Solar Phys. 282, 553.N/A: 1902, Publications of West Hendon House Observatory, Sunderland 2, 109-119. New

Edition 2010, University of Michigan Library.Nakazawa, Y., Okada, T., Shiokawa, K.: 2004, Earth, Planets and Space 56, e41.Ribes, J. C., & Nesme-Ribes, E.: 1993, Astron. Astrophys. 276, 549.Nevanlinna, H., Kataja, E.: 1993, Geophys. Res. Lett. 20, 2703.Nevanlinna, H., Pulkkinen, T.I.: 2001, J. Geophys. Res. 106, 8109.Odenwald, S.: 2007, Space Weather 5, S11005.Ogurtsov, M.G., Nagovitsyn, Y.A., Kocharov, G.E., Jungner, H.: 2002, Solar Phys. 211, 371.Oguti, T., Egeland, A.: 1995, J. Geomagn. Geoelectr. 47, 353.Owens, M.J., Lockwood, M.: 2012, J. Geophys. Res. 117, A04102.Owens, M.J., Usoskin, I.G., Lockwood, M.: 2012, Geophys. Res. Lett. 39, L19102.Owens, M.J., Forsyth, R.J.: 2013, Living Reviews In Solar Physics 10, No. 5.


Aurora Borealis

Pavon-Carrasco, F.J., Tema, E., Osete, M.L., Lanza, R.: 2014, Pure and Applied Geophysics,in press.

Pipin, V.V.: 2014, Astron. Astrophys. 346, 295.Peristykh, A.N., Damon, P.E.: 2003, J. Geophys. Res. 108, 1003.Raspopov, O.M., Kuzmin, I.A., Kharin, E.P.: 2007 Geomagnetism and Aeronomy, 47, 1.Rassoul, H. K., Rohrbaugh, R.P., Tinsley, B.A., Slater, D.W.: 1993, J. Geophys. Res. 98, A5,

7695.Rethly, A., Berkes, Z.: 1963, In Nordlicht-Beobachtungen in Ungarn, Budapest, Ungarische

Akademie der Wissenschaften.Richardson, I.G., Cane, I.V.: 2012, Journal of Space Weather and Space Climate 2, A01.Riley, P.: 2012, Space Weather 10, S02012.Riley. P., Lionello, R., Linker,J.A., Cliver, E.,Balogh, A., Beer, J.,Charbonneau, P.,Crooker,

N.,DeRosa, M., Lockwood, M., Owens, M., McCracken, K., Usoskin, I., Koutchmy, S.:2015, Astrophys. J. 802, 105.

Roach, F.E., Moore, J.G., Bruner, E.C., Cronin, H., Silverman, S.M.: 1960, J. Geophys. Res.65, 3575.

Robbrecht, E., Berghmans, D., Van der Linden, R.A.M.: 2009 Astrophys. J. 691, 1222.Rubenson, R.: 1882, Catalogue des aurores boreales observees en Suede, Kl. Sven. Vetenskap-

sakad. Handl. 18, 1-300.Saiz, E., Cerrato, Y., Cid, C., Dobrica, Y., Hejda, P., Nenovski, P.,Stauning, P., Bochnicek,

P., Danov, D.,Demetruscu, C., Gonzalez, W.D., Maris, G., Teodisev,D.,Valach,F.: 2013Journal of Space Weather and Space Climate 3, A26.

Salabert, D., Garca, R.A.,Palle, P.L., Jimenez, A.: 2011 Journal of Physics: Conference Series271, 012030.

Schlamminger: 1990, Mon. Not. Roy. Astron. Soc. 247, 76.Schove, D.J.: 1955, J. Geophys. Res. 60, 127.Schroder, W.: 1966, Gerl. Beitr. Geophys. 75, 436.Schroder, W.: 1988, Nature 335, 676.Schroder, W.: 2010, History of Geo and Space Sciences 1, 45.Schroder, W., Shefov, N.N., Treder, H.J.: 2004, Ann. Geophysicae 22, 2273.Schwabe, H.: 1844, Astronomische Nachrichten 21, 233.Sheeley, N.R., Howard, R.A.: 1980, Solar Phys. 67, 189.Shiokawa, K., Ogawa, T., Kamide, Y.: 2005, J. Geophys. Res. 110, A05202.Shirochkov, A.V., Makarova, L.N., Nikolaeva, V.D., Kotikov, A.L.: 2015, Adv. Spa. Res. 55,

211.Silverman, S.M., Blanchard, D.C.: 1983, Planet. Spa. Sci. 31, 1131.Silverman, S.: 1992, Rev. Geophys. 30, 333.Silverman, S.: 1995, J. Atmos. Solar-Terr. Phys. 57, 673.Silverman, S.: 2003, J. Geophys. Res. 108, 8011.Silverman, S.: 2006, Adv. Spa. Res. 38, 136.Silverman, S.: 2008, J. Atmos. Solar-Terr. Phys. 70, 1301.Silverman, S., Cliver, E.W.: 2001, J. Atmos. Solar-Terr. Phys. 63, 523.Singh, A.K., Sinha, A.K., Rawat, R., Jayashree, B., Pathan, B.M., Dhar, A.: 2012, Adv. Spa.

Res. 50, 1512.Siscoe, G.L.: 1980, Rev. Geophys. 18, 647.Sokoloff, D.: 2004, Solar Phys. 224, 145.Solanki, S., Schussler, M., Fligge, M.: 2000, Nature 408, 445.Solanki, S., Schussler, M., Fligge, M.: 2002, Astron. Astrophys. 383, 706.Sporer, G.: 1889, Nova Acta der Ksl. Leopold Carol. deutschen Akademie der Naturforscher

53, 283.Srivastava, N., Mathew, S.K., Louis, R.E., Wiegelmann, T.: 2009, J. Geophys. Res. 114,

A03107.Stauning, P.: 2011, Hist. Geo. Space Sciences 2, 1.Stetson, H.T., Brooks, C.F.: 1942, J. Geophys. Res. 47, 21.Suess, H.E.: 1980, Radiocarbon 22, 200.Taylor, C.J.: 1981, Artic 34, 376.Thordarson, T., Self, S.: 2003, J. Geophys. Res. 108, 4011.Tinsley, B.A., Rohrbaugh, R., Rassoul, H., Sahai, Y., Teixeira, N.R., Slater, D.: 1986, J.

Geophys. Res. 91, 11257.Traversi, R., Usoskin, I.G., Solanki, S.K., Becagli, S., Frezzotti, M.,Severi, M.,Stenni, B., Udisti,

R.: 2010, Solar Phys. 280, 237.


Vazquez et al.

Trigo, R.M., Vaquero, J.M., Stothers, R.B.: 2010, Climatic Change 99, 535.Tromholt, S.: 1898, Catalogue der in Norwegen bis Juni 1872 beobachteter Nordlichter, Jacob

Dybwad Forlag, Oslo.Tsurutani, B.T., Gonzalez, W.D., Kamide, Y., Arballo, J.K. (Eds): 1997, AGU Geophysical

Monographs, 98, 266.Uberoi, C.: 2011, Spa. Weather, 9, S08005.Usoskin, I.G., Mursula, K., Kovaltsov, G.A.: 2001, J. Geophys. Res., 106, 16039.Usoskin, I.G., Mursula, K., Solanki, S.K., Schussler, M., Kovaltsov, G.A.: 2002, J. Geophys.

Res. 107, 1374.Usoskin, I.G., Mursula, K., Kovaltsov, G.A.: 2003, Solar Phys. 218, 295.Usoskin, I.G., Mursula, K., Solanki, S.K., Schussler, M., Alanko, K.: 2004, Astron. Astrophys.

413, 745.Usoskin, I. G., Solanki, S. K., Kovaltsov, G. A.: 2007, Astron. Astrophys. 471, 301.Usoskin, I.G., Mursula, K., Arlt, R., Kovaltsov, G.A.: 2009, Astrophys. J. 700, L154.Usoskin, I.G.: 2013, Living Reviews in Solar Physics 10, 1.Usoskin, I.G., Arlt, R., Asvestari, E., Hawkins, E., Kapyla, M., Kovaltsov, G.A., Krivova, N.,

Lockwood, M., Mursula, K., OReilly, J., Owens, M., Scott, C.J., Sokoloff, D.D., Solanki,S.M., Soon, W., Vaquero, J.M.: 2015, Astron. Astrophys. 581, A95.

Vallance Jones, A.: 1992, Can. J. Phys. 70, 479.Vaquero, J. M., Gallego, M.C., Garcia, J.A.: 2003, J. Atmos. Solar-Terr. Phys. 65, 677.Vaquero, J. M., Trigo, R.M.: 2005, Solar Phys. 231, 157.Vaquero, J. M., Trigo, R., Gallego, M.C.: 2007, Earth, Planets, Space 59, e49.Vaquero, J.M., Vazquez, M.: 2009, The Sun recorded through History, Springer.Vaquero, J.M., Gallego, M.C., Barriendos, M., Rama, E., Sanchez Lorenzo, A.: 2010, Adv.

Spa. Res. 45, 1388.Vaquero, J.M., Gallego, M.C., Usoskin, I.G., Kovaltsov, G.A.: 2011, Astrophys. J. Lett. 731,

L24.Vaquero, J. M., Gallego, M.C., Dominguez-Castro, F.: 2013, Geofsica Internacional 52, 87.Vaquero, J.M., Kovaltsov, G.A., Usoskin, I.G., Carrasco, V.M.S., Gallego, M.C.: 2015, Astron.

Astrophys. 577, A71.Vaquero, J.M., Nogales, J.M., Sanchez-Bajo, F.: 2015, Adv. Spa. Res. 55, 1546.Vazquez, M., Vaquero, J.M.: 2010, Solar Phys. 267, 431.Vazquez, M., Vaquero, J.M., Curto, J.J.: 2006, Solar Phys. 238, 405.Vazquez, M., Vaquero, J.M., Gallego, M.C.: 2014, Solar Phys. 289, 1843.Verbanac, S., Vrsnak,B., Veronig, A., Temmer, M.: 2011, Astron. Astrophys. 526, A20.Vestine, E.H.: 1944, Terrestrial Magnetism and Atmospheric Electricity 49, 77.Visser, S.W.: 1942, Catalogue of Dutch Aurorae 1728 1940. Available from Jack Eddys

Compilation of Auroral Observation catalogues (rda.ucar.edu/datasets/ds836.0).Webb, D.F., Howard, R.A.: 1994, J. Geophys. Res. 99, 4201.Willis, D.M., Armstrong, G.M., Ault, C.E., Stephenson, F.R.: 2005, Ann. Geophysicae 23,

945.Willis, D.M., Davis, C.J.: 2015, Evidence for recurrent auroral activity in the twelfth and

seventeenth centuries, in New Insights from recent Studies in Historical Astronomy, ASSPVol. 43, 61.

Willis, D.M., Stephenson, F.R.: 1996, Quartely Journal of the Royal Astronomical Society 37,733.

Willis, D. M., Stephenson, F. R.: 2000, Ann. Geophys. 18, 1.Willis, D.M., Stephenson, F.R.: 2002, Highlights of Astronomy 12, 346.Willis, D.M., Stephenson, F.R., Fang, H.: 2007, Ann. Geophysicae 25, 417.Willis, D.M., Henwood, R., Stephenson, F.R.: 2009, Ann. Geophysicae 27, 185.Wolff, E.W., Bigler, M., Curran, M.A.J., Dibb, J.E., Frey, M.M., Legrand, M., McConnell,

J.R.: 2012, Geophys. Res. Lett. 39, L08503.Xu, Z., Pankenier, W., Jiang, Y.: 2000, East Asian archaeoastronomy: historical records of

astronomical observations of China, Japan, and Korea, Earth Space Institute (ESI) bookseries, vol. 5, Amsterdam: Gordon and Breach.

Yau, K.K.C., Stephenson, F.R., Willis, D.M.: 1995, A catalogue of auroral observations fromChina, Korea and Japan (193 B.C. A.D. 1770), Rutherford Appleton Lab. 82 p.

Yermolaev, Y.I., Lodkina, I.G., Nikolaeva, N.S., Yermolaev, M.Y.: 2013, J. Geophys. Res. 118,4760.

Zhang, Z.: 1985, Journal of the British Astronomical Association 95, 05.Zolotova, N.V., Ponyavin, D.I.: 2011, Astrophys. J. 736, 115.


Aurora Borealis

Zolotova, N.V., Ponyavin, D.I.: 2015, Astrophys. J. 800, 42.


long-term trends and gleissberg cycles in aurora borealis records

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