Steinitz, G., Piatibratova, O., Kotlarsky, P. Geological Survey of Israel, Jerusalem

steinitz@gsi.gov.il

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