the icmes magnetic field and the role on the galactic cosmic ray modulation for the solar cycle 23...

The ICME’s magnetic field and the role on the galactic cosmic ray modulation

for the solar cycle 23

Evangelos Paouris and Helen Mavromichalaki

National and Kapodistrian University of AthensPhysics Department

ESWW12 – 23-27 Nov. 2015 Oostende, Belgium

Overview

New ICME’s catalogue

Improvement of the CME-index with ICME magnetic field (Bz - component) and geomagnetic index Ap

Cosmic-Ray intensity modulation

Previous catalogues

Previous Catalogues Parameters

Richardson and Cane, 2010 Start/End times of sheath and ICME,VI, Vmax, Vtransit, B, MC, Dst, SOHO/LASCO association

Zhang et al., 2007 Start/End times of shock and ICME,VI, width, Dst, flare association

SOHO/LASCO association

Jien et al., 2006 Start/End times of shock and ICME,Vmin, Vmax, Bmax, Comments

Mitsakou and Moussas, 2014 Start/End times of sheath and ICME

Each one has important information but these are separated works

ONE list with as many as possible information per CME


ICME identificationACE SOHO / LASCO

ICMEShock


New Catalogue with 48 parameters for each CME/ICME

Start time of the disturbance/discontinuity, Start/End time of the ICME, background conditions (before the arrival of the ICME), Shock/MC existence,

Vinitial, Vicme/max, Vdist/max, Vtransit, Binitial, Bicme/max, Bdist/max, Bz_dist/icme/min, plasma parameters (plasma β, Tp, Np, alpha ratio), Dst min

and time, Ap max and time, SOHO/LASCO CME association date/time and angular width, solar flare association C,M,X-class, peak time, AR region with

coordinates, Comments about the event

161 events for solar cycle 23

(This new catalogue is going to be published very soon)


First attempt for CME-index with magnetic field

ICME

Magnetic field - |

B|

Transit Velocity -

Vtr

Angular width - w

maxmax max

trIi

I tr

VB wB

PV w

0 3iP

Pi = 3 (maximum value) for “Halloween event” 29 October 2003 with:

BICME = 31.72 nT, Vtransit = 2235 km/s and w=360° (halo)

(Paouris and Mavromichalaki, 2015)


A more geoeffective index

ICME

Bz Magnetic field minimum

value - Bz

Transit Velocity - Vtr

Angular width - w

maxmin,

max max2

trz

z tri

VB w ApB V

Pw Ap

,20 4iP

Ap geomagnetic index - Ap


The new CME-index

max,1

max

0.23 0.77iNc VpNc Vp

P

“Background index”

(Paouris, 2013) and (Paouris et al., 2015a)

October-November 2003

“Geoeffective index”

maxmin,

max max2

trz

z tri

VB w ApB V

Pw Ap


The new CME-index

The new final combined formula has the form:

m, ,2

ax1ii i

NP PPN

The factors α and β are taking into account the phase of the solar cycle and the factors γ and δ are taking values in order to maximize the correlation coefficient between Pi-index and Cosmic Ray intensity

ICMEs monthly number CME-index based on

ICMEs

Background CME-index


Galactic Cosmic-Ray modulationThe best model before the ICME index:

“Solar” modelVariables: Sunspot Number (Rz), CME-index (Pi), mean

Magnetic Field (MF) and Polar Field (PF) of the Sun

The values of Pi based on the data of CMEs with angular width greater than 15° are produced by the monthly number of CMEs (Nc) and the mean plasma velocity (Vp) with the following relation:

max,1

max

0.23 0.77iNc VpNc Vp

P

31 2 3 410 MF PFz iI C a R a P a a

RMSD: 9.5%

(Paouris et al., 2015)


Galactic Cosmic-Ray modulationThe best model with the new Pi-index using

magnetic fields of the ICMEVariables: Sunspot Number (Rz), CME-index (Pi), mean

Magnetic Field (MF) and Polar Field (PF) of the Sun

Same Minimum for the observed and calculated by the model for the first

time!

Observed CR intensity from LMKSCalculated CR intensity

RMSD: 7.5%


Comparison between the models

Previous model New model

Statistics

Cor. Coef. r = 0.9255Conf. level 95%

Root-MSE (SD) 0.09543

Statistics

Cor. Coef. r = 0.9542Conf. level 95%

Root-MSE (SD) 0.07537


Conclusions

• For the first time a new ICME catalogue with so many information for each event is presented and also the magnetic field of the ICMEs is taken into account for the study of the CR modulation.

• The Pi-index is considered as a combination of the background values (Pi,1) and the ICMEs characteristics (Pi,2) which are associated with geomagnetic storms. Very high correlation coefficient (r = -0.91) between this index and the CR intensity, is found.

• The modulation of CR intensity gave the best approximation between observed and calculated values up to now with a RMSD ≈ 7.5%

• This new model approaches very well also the minimum of CR intensity (October/November 2003). The minimum of observed CR intensity coincides with the calculated by the model for the first time.

• The comparison between the last two models revealed a better cross correlation coefficient for the new model with r = 0.954 (conf. level = 95%)


Thank You!


the icmes magnetic field and the role on the galactic cosmic ray modulation for the solar cycle 23...

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