Steinitz, G., Piatibratova, O., Kotlarsky, P. Geological Survey of Israel, Jerusalem
Solar radiation tidal forcing of radon signals in subsurface air
Monitoring sites
Solar irradiance related components - S1, S2 dominate = solar tide
Main components Name Period (hr) Cycles (Day-1)
Principal lunar declinational O1 25.82 0.9295
Solar diurnal S1 24.00 1.0000
Principal lunar M2 12.42 1.9324
Principal solar S2 12.00 2.0000
Cycle / day
0 1 2
Am
plit
ud
e
0
100
200
300
400
O1
N2
M2
S2
S1
NW Gulf Elat, Rn in seawaterShore gravel; 2m deep, 130 daysGravel; NW Dead Sea; 1.5m
Granite; Elat; 54m
Periodograms of the diurnal components of radon signals in subsurface air
19WDay 4100-4700
Cycle / day
0 1 2
Am
plitu
de
0
20
40
60
80
100E-3; Days 4356-4441
Cycle / day
0 1 2
Am
pli
tud
e
0
20
40
60
80
S2
S1
S2
S1
Signal types, periodicity, Solar tide components
Period Tidal component Rn Acronym
1. Daily signals 24-, 12-hours S1, S2DR
2. Multi-Day (non-periodic)MD
3. Annual radon 365.2 days SAAR
4. Semi-annual radon 182.6 days SSASAR
5. Ternary annual radon 121.7 days STATAR
6. Multi-Year (non-periodic?)MY
Gravity tide - rare
Granite; Elat; 54m
Geophysical background
CWT analysis: Annual modulation of the amplitude of DR signal (S1 and S2) occurs as a compounded feature
Experimental replication
The reasoning• Dominance of solar tidal frequencies of annual, and daily scale• Annual modulation of the amplitude and phase of daily and sub daily
tidal frequencies• Systematic multi-year variation of signal and periodic characteristics • Occurrence different locations, at depth to >100 meter• Similar phenomena in laboratory experiments of radon in confined air
And• Negation of climatic influences• [Lack of gravity tidal frequencies]
IMPLIES
• Periodicity is forced by solar tide• A component of solar radiation?
Intraplate• Depth: 1.2 m & 90 meter
• Massive syenite
Southern Arava• Array of stations, 20 km sector
• In Precambrian basement rocks
• Depth 2 to +100 meter
Radon monitoring arrays along the Dead Sea Rift (DSR)
High temporal resolution monitoring of radon, using alpha & gamma detectors, is carried out at several arrays located in arid southern Israel. Monitoring, at a resolution of 15-minutes, is conducted at depths ranging from 1.5 to 120 meter.
Temporal phenomena encountered differ among sites, but have similar fundamental characteristics.
NW Dead Sea• Array of stations, along a
20 km sector
• 1.5 m deep in unconsolidated gravel
17W
21W
GAV
Amram
Roded
Elat Granite
Radon (Rn-222) occurs at highly varying levels as a trace component in subsurface air (geogas). It is measured
by alpha and gamma activity during the decay of radon and its progeny. Radon in geogas exhibits systematic
temporal variations composed of periodic and non-periodic signals spanning several orders of magnitude in time
– multi-year, annual to daily and sub-daily duration. Analysis of extensive data sets from key sites 200 km apart
in the arid desert of southern Israel demonstrated that the periodic variations, are observed to a depth of >100
meter. A component of solar irradiation tide was suggested (References) as the driver of these periodic
phenomena at depth.
The issue of external forcing of radon signals was tested experimentally using alpha and gamma detectors
recording radon within a confined volume of Air. The setup consisted of an isolated volume (640 L) of air with
radon, the latter diffusing into the upper air volume from U bearing ground phosphorite (376 Kg). Alpha and
gamma radiation emitted from radon in the tank air varies spatially and temporally. A 4-year time series shows
multi-year and multi-day signals and especially periodic signals of annual and daily scale. The diurnal variations
are dominated by periodicities of 24-, 12-, and 8-hours which are attributed to the Solar tidal constituents S1, S2,
and S3. Periodicities indicative for diurnal gravity tide (O1, M2; Lunar influence) are clearly lacking. Profound
external geophysical influence is further indicated by compounded relations that occur as annual modulation of
the amplitude and phase of the diurnal constituents S1, S2 and S3.
Further insight is derived from the long term variations in time series from the geological environment and from
the experiment. In addition to the annual periodicity clear semiannual and ternary annual signals are
demonstrated. They are attributed to the solar tidal constituents Sa, SSa and STa.
REFERENCES
1. Steinitz, G., O. Piatibratova, and S. M. Barbosa, 2007. Radon daily signals in the Elat Granite, southern Arava, Israel, J. Geophys. Res., 112, B10211, doi:10.1029/2006JB004817.
2. Steinitz, G., Piatibratova, O., 2010a. Radon signals in the Gavnunim intrusion, Makhtesh Ramon, Israel. Geophys. J. Int. 180, 651–665.
3. Steinitz, G. and Piatibratova, O., 2010. Radon signals at the Roded site, Southern Israel, Solid Earth, 1, 99-109, doi:10.5194/se-1-99-2010.
The multi-year rising trend observed at Experiment, 17W and Amram sites. The temporal pattern is measured by alpha and gamma detectors in Amram and in the Experiment.
Semi-annual radon signals are superimposed on the annual signal recorded by alpha-L and gamma-C. A similar semi-annual pattern is absent in the ambient temperature.
Historgram of values (17W, Gamma detector)
Counts 1e+5 2e+5 3e+50
5000
10000
Bias
17W
1999 2001 2003 2005 2007
Cou
nts
5.0e+4
1.0e+5
1.5e+5
Day 2500 3000 3500 4000 4500 5000 5500
Measured Long-term biasAnnual Radon (AR)Long-term (MY)
Spectra for alpha and gamma measurements (9 yrs) show clear peaks characteristic for annual and semi-annual periodicity (365.2 and 182.6 cycle/day).
AlphaGamma
Day since 1.1.1992
5600 5800 6000 6200 6400 6600 6800
1000
1100
1200
1300
1400
2008 2009 2010 2011
Alpha-HAlpha-L
Day since 1.1.1992
5600 5800 6000 6200 6400 6600 6800
Co
un
ts/1
5-m
in
2.2e+5
2.3e+5
2.4e+5
2.5e+52008 2009 2010 2011
Spectral analysis: SA. SSA, STA periodicities
Spectra of alpha and gamma measurements (Experiment - 4yrs) show clear peaks characteristic for annual and semiannual periodicity
(365.2 and 182.6 cycle/day).
gamma-C
Cycle/day
0.00 0.01 0.02 0.03 0.04 0.05
Am
pli
tud
e
0
2500
5000
Mean of two alpha detectors
Cycle/day
0.00 0.01 0.02 0.03 0.04 0.05
Am
pli
tud
e
0
25
50
75
Smoothed pattern of• AR & SAR signals• (maxima of T – lags)
Day since 1.1.1992
5750 6000 6250 6500 6750
Cou
nts/
15-m
in (
gam
ma-
C)
2.3e+5
2.4e+5
Cou
nts/
15-m
in (
alph
a)
1100
1200
1300
1400
2008 2009 2010 2011
oC
10
15
20
25
30
Gamma-C Alpha-HAlpha-LTemperature
Amplitude and phase are extracted by applying FFT windowing, where each point represents a (consecutive) 21-day time interval.
Annual modulation of the periodic components (amplitude & phase) of the DR signal in Experiment.
• Annual variation of the amplitudes of the daily components is dissimilar for gamma and alpha time series - showing opposite temporal patterns!
Amplitude Phase
1
2
4
5
6
2008 2009 2010
Alpha H
20
40
60
80
2008 2009 2010
Gamma C
Am
plitu
de (
coun
ts x
103 )
0
5
10
Ph
ase
(ra
d)
2
6
7
Alpha L
Days since 1.1.1992
5500 6000 6500
0
2
4
6
8
10
12
14
S1S2S3
Days since 1.1.1992
5500 6000 6500
0
2
4
6
21W: Annual and semi-annual modulation of the amplitude of the diurnal periodicities S1 and S2
S1A
mpl
itude
(x1
000)
0
25
50
75
2004 2005 2006 2007 2008 2009
S2
Days since 1.1.1992
4500 5000 5500 6000 6500
Am
plitu
de (
x100
0)
0
5
10
15
Alpha (BGO)
Cycle/day
0.000 .005 .010 .015 .020
Am
pli
tud
e
0
10
20
30
40
50
60
AR
SAR
Gamma (BGO)
Cycle/day
0.000 .005 .010 .015 .020
PS
D S
SA
0
1e+9
2e+9
3e+9
4e+9
5e+9AR
SAR
Amram
Day 4000 5000 6000 7000
Gam
ma
(co
un
ts)
4000
6000
8000
10000
12000
14000
2002 2004 2006 2008 2010
Alp
ha
(co
un
ts)
0
100
200
GAV: Annual modulation of the amplitude of the diurnal periodicities S1 and S2
GAV: Daily averages at 1.2 meter
2003 2004 2005 2006 2007 2008
Dai
ly m
ean
(cou
nts)
0
500
1000
ampl
itude
0
50
100
150
2003 2004 2005 2006 2007 2008
S 2S 1
Roded: Annual variation of amplitude of the diurnal periodicities S1, S2
1999 2001 2003 2005 2007 2009
Am
plit
ud
e
0
50
100
150S1
Days since 1.1.19923000 4000 5000 6000
0
50
100S2
Roded: Multi-year variation of phase of the diurnal periodicities S1, S2
1999 2001 2003 2005 2007 2009
ph
ase
(rad
)
0
2
4
6
S1
Days since 1.1.1992
3000 4000 5000 60000
2
4
6
S2
Elat Granite:• Measured pattern• Smoothed time series - AR signal and SAR signal as an asymmetry • Modulation of the residual time series - AR and SAR signal
Days since 1.1.1992
3400 3600 3800 4000 4200 4400 4600 4800 5000
Co
un
ts/1
5-m
inu
te
-200
0
200
400
Co
un
ts/1
5-m
inu
te
-100
0
100
200
300
400
500Year2002 2003 2004 2005
MSMDDR
Phosphorite
Alpha-HGamma-C
Alpha-L
(Rn source)
(air)
Metal tank, tight
Nuclear radiation - summer peak times of annual signal
2010
Day since 1.1.1992
6740 6750 6760 6770 6780 6790 6800 6810
Gam
ma
2.420e+5
2.423e+5
2.425e+5
2.428e+5
Alp
ha
1375
1380
1385
1400
oC
26.8
27.0
27.2
27.4
2007
5640 5650 5660 5670 5680 5690 5700
Gam
ma
2.430e+5
2.435e+5
2.440e+5
Alp
ha
1330
1335
1350
1355
1360
oC
26.0
26.1
26.2
26.3
26.4
26.5
2008
Day since 1.1.1992
6020 6030 6040 6050 6060 6070
Gam
ma
2.400e+5
2.405e+5
2.410e+5
2.415e+5
Alp
ha
1330
1335
1340
1345
1355 oC
26.6
26.8
27.0
Gamma-C Alpha-HAlpha-LTemperature
2009
Day since 1.1.1992
6370 6380 6390 6400 6410 6420 6430
Gam
ma
2.430e+5
2.435e+5
Alp
ha
1390
1400
oC
26.0
26.2
30 days
AR