Cycles of the Solar Wind Flux at the Front of the Earth’s Magnetosphere

7/27/2019 Cycles of the Solar Wind Flux at the Front of the Earths Magnetosphere

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Cycles of the Solar Wind Flux at the Front of the Earths MagnetosphereY. Shopov and D. StoykovaCitation:AIP Conf. Proc. 1356, 192 (2011); doi: 10.1063/1.3598105View online: http://dx.doi.org/10.1063/1.3598105View Table of Contents: http://proceedings.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=1356&Issue=1Published by theAmerican Institute of Physics.Related Articles

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Cycles of the Solar Wind Flux at the Front of the

Earths Magnetosphere

Y. Shopovand D. Stoykova

University Center for Space Research and Technologies,

St. Clement of Ohrid University at Sofia,

5 James Bourchier Blvd., BG-1164 Sofia, Bulgaria

Abstract. We studied various long solar wind proxy records in order to reveal prolonged solar wind cycles. Inverted rate

of atmospheric 14C production as derived from the standard radiocarbon calibration curve represents good proxy record ofthe past variations of the solar wind flux at the upper atmosphere because it modulates the galactic cosmic rays flux,

which produces the radiocarbon there. We made periodogramme time series analysis of the inverted rate of atmospheric14C production record in order to obtain the solar wind cycles. In such a way, we found cycles of 11500, 1670, 1420,

1280, 924, 835, 787, 750, 663, 610, and 545 years in this solar wind proxy record.Records of the intensity of the geomagnetic dipole are also proxy records of variations of the solar wind flux, because

it modulates the geomagnetic field. We made periodogramme time series analysis of the one long record of the intensityof the geomagnetic dipole in order to obtain the solar wind cycles. In this way we found cycles of 11 500, 4400, 3950,2770, 2500, 2090, 1960, 1670, 1460, 1280, 1195, 1145, 1034, 935, and 835 yrs in this solar wind proxy record. We have

confirmed the solar origin of all this cycles by their detection in an independent solar luminosity proxy record.The 11 500-yr cycle was found previously to be the most intensive cycle in the 14C calibration record and was

interpreted to be of geomagnetic origin. Our studies suggest that this is a solar cycle modulating the geomagnetic field.

We determined the solar origin of strong cycles with duration of 11500, 4400, 3950, 2770, 2500, 2300, 2090, 1960, 1670,1460, 1280, 1195, 1145, 1034, 935, 835, 814, 775, 750, 660, 610, 550, and 538years and of many weak cycles withduration from one to five centuries. This was achieved by their detection in proxy records of solar luminosity,atmospheric 14C production and the intensity of the geomagnetic dipole. The main variations in the last two records areknown to be produced by the solar wind while the first record is absolutely independent on the geomagnetic field, so non

of these cycles can be of terrestrial origin.The main variations in the 14C and geomagnetic field records are produced by the solar wind. Known decadal and

even centennial solar cycles have negligible intensity (100 times less intensive) relative to these cycles. These millennialsolar luminosity cycles can produce climatic variations with intensity comparable to that of the orbital variations known

to produce the glacial periods on Earth.We discovered a sub-annual cycle of 27 days in very high-resolution soil surface temperature proxy records,

attributed to solar rotation, which causes the periodic appearance of active zones on the visible solar surface, which arethe major emitters of solar wind. Solar wind modulates cosmic ray flux at the Earth, while cosmic rays influence theatmospheric transparency, thus producing a multiplication of solar variations in insolation. Hence small variations of the

solar activity can produce a measurable influence on insolation.

Keywords: solar wind, solar irradiance, solar activity, solar cycle, solar rotation, proxy records; atmospheric 14CproductionPACS: 96.60.Q, 96.60.Tf, *96.60.tj, 96.60.Tf, *96.60.th, 96.60.qe, 96.60.Ub, 96.60.-j, 96.60.Ly, 92.60.Vb, 94.20.wq,96.60.Vg

3rd School and Workshop on Space Plasma PhysicsAIP Conf. Proc. 1356, 192-203 (2011); doi: 10.1063/1.3598105

2011 American Institute of Physics 978-0-7354-0914-9/$30.00

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1. INTRODUCTION

Solar system is a giant dynamo machine: rotation of magnets (planets) in the external variable magnetic field of theSun carried by the solar wind (SW) produces powerful induced electric currents (like in electric power generators).Such currents are observed to flow around the Earth. They generate a magnetic field which superposes Earthsmagnetic field and produces its variations [1].

Variations of solar irradiance have been small during the period of direct satellite observations[2], but can be

much bigger during geological periods of time [3, 4, 5].Crowley [6] estimated that over the last 1000 years as much as 4164% of pre-anthropogenic decadal-scale

temperature variations are due to changes in solar irradiance and volcanism. Here we consider impact of variationsof cosmic rays, solar wind and solar irradiance on Earths climate. A link between cosmic rays intensity and cloudcover has been discovered by Ohring and Clapp [7] and proven by comprehensive measurements [8]. Cosmic rayscan modulate atmospheric transparency [8].

2. INSTUMENTAL DATA ON SOLAR WIND VARIATIONS

First we studied cycles of the solar wind flux in the available instrumental records (Fig. 1). For this purpose wechoused OMNI multi-source spacecraft data set of daily averaged solar wind plasma flow speed [km s1] and ionnumber density [N/cm3] near the magnetosphere from January 1995 to July 2010 [9]. This is the best data set ofuninterrupted time series of solar wind measurements for determination of the cycles of variations of the solar wind.

OMNI data set is a compilation ofACE, Wind,IMP 8and Geotail spacecraft data sets made by GSRC/Space PhysicsData Facility [10]. We calculated cycles of the solar wind speed (Fig. 2) and ion density (Fig. 3) by Real Space

periodogramme analysis. Both solar wind speed and ion density demonstrate groups of cycles with duration between27 and 30 days (Figs. 2, 3) and another group of cycles with half of its duration (between 13.5 and 15 days). Bothgroups can be attributed to solar rotation. Solar wind have two componentssteady one, which comes from thepolar openings of the solar magnetic field and variable one, which comes from coronal holes of the solar magneticfield. Coronal holes form above the unipolar pairs of sunspots [11]. Sunspots appear on the visible surface of the Sunwith period of 27 to 30 days depending on their heliographic latitude [11]. Period which one sunspot spends on the

visible surface of the Sun is half of the solar rotation, so varies from 13.5 and 15 days depending on theirheliographic latitude. Same periods must exist in appearance of the coronal holes on the visible surface of the Sunand therefore also in the solar wind variations. One would expect that this would cause single broad peaks between13.515 and 2730 days in calculated power spectra, but the identical calculation on instrumental data of variationsof the solar irradiance produce similar groups of cycles (Fig. 4). This suggests that unipolar pairs of sunspots andphotospheric faculae appear only on specific heliographic latitudes or have also a specific motion on the solarsurface, which is not dependent on the differential rotation of the Sun.

3. SOLAR IRRADIANCE

In order to study cycles of the solar irradiance we studied two types of data:

3.1. Instrumental records of solar irradiance

In order to study cycles of the solar irradiance in the available instrumental records (Fig. 4) we choused empiricalsolar irradiance model SOLAR2000 Research Grade version 1.15 [12], which contains compilation of variations of

the solar constant since February 14, 1947 through December 31, 2000. We calculated cycles of the solar irradiancein this record by Real Space periodogramme analysis. In addition to the well known 11 year cycle it demonstratesgroups of cycles with duration between 27 and 30 days (Fig. 4). Sunspots and photospheric faculae around themappear on the visible surface of the Sun with period of 27 to 30 days depending on their heliographic latitude [11].Photospheric faculae have much higher temperature then the average effective temperature of the solar surface, somay raise solar irradiance in a small degree. Probably they are responsible for the observed variations of the solar

irradiance data [12] and for the group of peaks with duration between 27 and 30 days (Fig. 4).

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FIGURE 1. Daily averaged solar wind plasma Flow Speed [km s1] and Ion Density [N/cm3] near the magnetosphere9

from

January 1995 to July 2010 [10].

3.2. Proxy records of solar irradiance

In this work, we use experimental luminescent speleothem proxy records of the solar insolation and solarirradiance, which appear to be most convenient for calculation of prolonged cycles of solar irradiance [13]. Usedinstruments and their characteristics are described in [14].

A luminescence record from a speleothem from Cold Water Cave demonstrated high correlation (R

2

= 0.90) withthe Solar Irradiance index obtained from direct observations since 1700 AD, with no detectable delay between the

two records [15].Shopov et al. [4] measured a luminescent record in speleothem JC11 from Jewel Cave, South Dakota, US. This

record has resolution of 34 years and precision of measurements better than 1%. Timing of the record is controlledby six TIMS U/Th dates with 2-sigma error of 0.85.5 kyrs [5]. Here we study millennial and centennial cycles inthe record.

We measured a luminescent solar insolation proxy record in a speleothem from Duhlata Cave, Bulgaria (Fig. 5).It is dated by four TIMS U/Th ages and coincides with the JC11 record within the experimental uncertainty. These

solar insolation proxy records contain orbital cycles (Fig. 5(b)) and a large number of solar irradiance cycles withdurations from several centuries to 11 500 years (Table 1).

The luminescence of calcite speleothems precipitated in vadose (air-filled) caves depends exponentially uponsoil temperatures that are determined primarily by solar infrared radiation in the case when the cave is covered only

by grass or upon air temperatures where there is forest or bush cover. In the first case, the microzonality of theluminescence detected in speleothems can be used as an indirect Solar Insolation index (like records from ColdWater Cave, Jewel Cave and Duhlata Cave) and in the second as a paleotemperature proxy. So, in terms of thedependence on cave site conditions we may speak about solar sensitive and temperature sensitive paleo-

luminescence speleothem records as in tree ring records, but in our case records may depend entirely on temperatureor on solar irradiation [15, 16]. Used Laser luminescence microzonal analysis uses high optical magnification

allowing sampling resolution of less than a day in some instances [14].

Ion Density

0

10

20

30

40

50

60

0 1000 2000 3000 4000 5000 6000

days

IonD

ensity[N/cm^3]

Flow speed

0

100

200

300

400

500

600700

800

900

1000

0 1000 2000 3000 4000 5000 6000

days

Flowspeed[km/s]

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FIGURE 2. Intensity of cycles of daily averaged solar wind plasma flow speed near the magnetosphere (OMNI-2 data [9]) fromJanuary 1995 to July 2010 calculated by Real Space periodogramme analysis.

FIGURE 3. Intensity of cycles of daily averaged solar wind ion density near the magnetosphere [9] from January 1995 to July2010calculated by Real Space periodogramme analysis.

0

0.1

0.2

0.3

0.4

0.5

0.6

0 10 20 30 40

days

IofIondensitycycles

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1000 2000 3000 4000

days

IofIondensitycycles

0

5

10

15

20

25

30

0 200 400 600 800 1000 1200 1400 1600 1800 2000

days

IntensityofSWvelo

citycycles

0

5

10

15

20

0 10 20 30 40

days

IntensityofSWvelocitycycles

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TABLE 1. Variations of the solar constant in Wm2 (VSC) and in % of the solar constant (PSC) compared with cycles(Fig. 8) of variations of the intensity of the geomagnetic field (GEOM), cycles (Fig. 6) of the inverted rate of

atmospheric-14 production [17] calculated by Shopov et al [5] in % of the solar constant with the same computercode using Real Space periodogramme analysis and the duration of cycles of the inverted rate of atmospheric -14

production [18] in Italic calculated by us with the same computer code (Fig. 7). Cycles present not only in the solarconstant but also in geomagnetic field or-14 must be of solar origin. They are outlined in bold. Last column of the

table contains also cycles of the inverted atmospheric 14-C production solar wind proxy in years calculated in differentworks with different types of time series analysis (see Table 2)

Cycle

[Yrs]

Error

[Yrs]PSC

[%]

VSC

[Wm2]

GEOM

[%]

C-14

[%]

C 14

[Yrs]

11500 +1900/1150 7.33 100.6 7.33 7.33

6160 +/410 3.02 41.5

4400 +/209 1.78 24.4 6.2

3950 +/148 1.83 25.1 4.32

3400 +/126 1.76 24.1

2770 +/80 0.92 12.6 3.25

2500 +/67 1.19 16.3 4.7

2300 +/

60 0.91 12.5 2079

24002090 +/50 0.53 7.28 2.26 20792400

1958 +/42 0.82 11.26 2.82

1770 +/35 0.62 8.5

1670 +/30 0.66 9.1 1.01 0.73

1460 +/23 0.73 10 2.42 1420 +/1000

1280 +/18 0.35 4.8 0.71 1420 +/1000

1195 +/15 0.33 4.5 1.22 0.4 1420 +/1000, 1183

1145 +/14 0.33 4.5 1.92

1034 +/16 0.31 4.26 1.62

935 +/9.4 0.22 3.02 1.2 924 +/40, 909965

835 +/7.5 0.26 3.6 0.6 0.56

814 +/

7.2 0.19 2.6 787 +/

29775 +/6.5 0.17 2.3 787 +/29, 733805

750 +/6.0 0.19 2.6 0.56 733805

670 +/5.5 0.15 2.06

660 +/4.8 0.18 2.47 663+/39, 649717

610 +/3.9 0.13 1.78 0.48

570 +/3.5 0.15 2.06

550 +/3.3 0.13 1.78 545 +/15

538 +/3.1 0.15 2.06 545 +/15

480 +/2.5 0.10 1.37 482 +/21, 493512

455 +/2.3 0.11 1.57

448 +/2.1 0.07 0.91

416 +/1.9 0.10 1.37 433 +/9, 413440

405 +/

1.8 0.07 0.96 378 +/

13, 385

399

342 +/1.27 0.06 0.81 348 +/6, 353357

317 +/1.08 0.07 0.91

291 +/0.904 0.06 0.83 299 +/4, 299308

287 +/0.698 0.06 0.76 283 +/4

254 +/0.378 0.08 1.06 256 +/3, 229232

186 +/0.286 0.06 0.79 181.3+/1.5, 183208

162.5 +/0.282 0.06 0.83 155175, 162+/1.2

156.5 +/0.267 0.06 0.76 155175, 156 +/1.2

155.9 +/0.265 0.06 0.79 141151, 156 +/1.2

118.2 +/0.152 0.05 0.68 114132, 125 +/0.8

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Cycles of variations of the Solar constant

FIGURE 4. Cycles of variations of the solar constant since February 14, 1947 through December 31, 2000 data [12] calculatedby Real Space periodogramme analysis.

Our experimentally measured solar insolation proxy records contain variations produced by both Earths orbitaland solar irradiance variations [4]. In order to obtain a record of the past solar irradiance (Fig. 5(c)) it is necessary toextract the orbital variations from an insolation record by a band-pass filter set for the orbital frequencies (Fig. 9(b)).The remaining signal contains only solar irradiance self-variations (Fig. 9(d)).

FIGURE 5. A solar insolation luminescence proxy record from Duhlata Cave, Bulgaria (A). Sum of the orbital variations (B)

and solar irradiance (C) extracted from the record. It demonstrates that during the last 60000 years intensity of solar irradiance

variations prevailed over the orbital variations in solar insolation. All curves are presented in decimal logarithm relative units.

0

0,0001

0,0002

0,0003

0,0004

0,0005

0 5 10 15 20 25 30 35 40 45 50

days

SolarConstant(W/m2)

A

0.8

0.9

1

1.1

1.2

1.3

1.4

0 50000 100000 150000 200000 250000Years B.P.

LgI(R.U.)

B

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0 50000 100000 150000 200000 250000

Year B.P.

LgI(R.U.)

C

-0.2

-0.1

0

0.1

0.2

0 50000 100000 150000 200000 250000

Years B.P.

LgI(R.U.

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In order to quantitatively compare the intensities of all cycles present in our data we have designed a special

algorithm and computer code that plots the periodogramme in the coordinates Cycle Intensity/Period. It is calledReal Space periodogramme analysis [5] and is used in all calculations of cycles in this paper. It allows comparisonof the real intensity of the solar irradiance variations with the intensity of the variation of the insolation produced by

the precession cycles (as precisely calculated by Berger and Loutre [19]). This way we calibrated obtained cycles ofsolar irradiance in % of the solar constant or in Wm2 (Table 1).

FIGURE 6. Cycles in the inverted atmospheric 14-C production solar wind proxy data [17].

Cycles in 14C inverted calibration curv e

0

5

10

15

0 1000 2000 3000 4000 5000

Years

Cycles

in14C[permil]

FIGURE 7. Cycles in the new inverted atmospheric 14-C production solar wind proxy data [18].

FIGURE 8. Cycles in the past Geomagnetic Field Intensity (virtual axial dipole momentum) data [20].

We obtained independent experimental evidence that low- frequency variations of geomagnetic dipole moment

have solar origin. It is demonstrated in Table 1. Here we calculated cycles in the record of the intensity of

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geomagnetic dipole moment during the last 80 000 years [20] and in a long record of the solar irradiance [13], which

is completely independent on the geomagnetic field [21, 22]. All cycles of geomagnetic field exist also in variationsof the solar irradiance (Table 1) which demonstrates their solar origin.

Solar wind modulates the geomagnetic dipole moment which modulates cosmic rays flux [23] producing14

C. So

the inverted variations of the 14C production can be used as solar wind proxy [24]. We studied long 14C solar windproxy records in order to reveal prolonged solar wind cycles. It is widely used for this purpose (Table 2). Invertedrate of atmospheric 14C production as derived from the standard radiocarbon calibration curve represents good proxy

record of the past variations of the solar wind flux at the upper atmosphere because it modulates the galactic cosmicrays flux, which produces the radiocarbon there.

Sonett [25] found that a cycle with a period of about 900 years has intensity 57 times higher than that of thewell-known centennial cycle in the 14-C solar proxy record. Stuiver and Braziunas [26]

calculated MEM- spectra of

the same record and claimed that changes occur in the Suns convective zone with a fundamental oscillatory modeof about 420 yr. period. and that centennial and sub-centennial cycles are about one twentieth of the strength of this420-yr cycle. Although the uncertainty of the proportion between intensities of different cycles in the spectracalculated by these authors cannot be estimated, their work suggests that longer solar cycles are about one order ofmagnitude stronger than the solar cycles detected by direct measurements. Calculated periodogrammes of the JC11

luminescent record demonstrated that the solar cycle of about 900 years has intensity only 34% of the 11 500-yr

cycle and the solar cycle of about 420 years has intensity less than 2.5% of the 11 500-yr cycle (see Table 1); thusthe 11 500-yr cycle should have intensity of several orders of magnitude higher, than the observed centennial andsub-centennial cycles.

The 11500 year cycle was found previously to be the most intensive cycle in the 14C calibration record and wasinterpreted to be of geomagnetic origin [17]. Our recent studies suggest that this is a solar cycle modulating the

geomagnetic field. We determined the solar origin of other strong cycles with durations of 11 500, 4400, 3950, 2770,2500, 2300, 2090, 1960, 1670, 1460, 1280, 1195, 1145, 1034, 935, 835, 814, 775, 750, 660, 610, 550, and 538 years

and many weak cycles with duration from one to five centuries (Table 1). This was achieved by their detection inproxy records of speleothem luminescence [4], 14-C [17, 18] and the intensity of the geomagnetic dipole [20]. Themain variations in the last two records are known to be produced by the solar wind.

TABLE 2. Cycles of the inverted atmospheric 14-C production solar wind proxy in years calculated in different workswith different types of time series analysis. In result of the different precision of different calculations duration of the same

cycle differs in some degree in the different calculations. Last column of the table shows the deviations in thedetermination of the duration of the same cycle in the 14-C Solar index

Suess [27] Sonett [25] Sonett [28] Damon, Sonett [29] 14-C Solar index

20.1

20.8 2026

26.3

32.7 33

88 88

104 104 105 105

114 131 114132

141 146151 141151

155 177 175 155175

202 183 208 192, 207 (208) 183208

229 232 229232

308 299 299308

357 353 353357

399 385 385399

413 427, 440 413440

498 493 504, 512 493512

715 717 649 649717

753 733, 805 733805

930 955 965 909 (955) 909965

1183 1183

2400 2079 2311 2241(2272) (2385) 20792400

4747 4750

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FIGURE 9. (A) Luminescence record JC11 from Jewel cave, South Dakota, USA (Top) The TIMS U/Th dating points are

shown by points with 2 error bars. (B) Orbital components of Solar Insolation variations extracted from the JC11 record by aband-pass Tukey filter set for the frequencies of 41, 23 and 19 kyrs of the orbital cycles, (C) sum of the orbital variations. (D)

Solar Luminosity variations extracted from JC11 Solar Insolation proxy record by subtracting of the sum of the orbital variations

from the JC 11 luminescent record [5].

A

B

C

D

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0.45

0.47

0.49

0.51

0.53

0.55

0.57

0.59

0.61

0.63

0.65

0 1 2 3 4 5

years

Lg(I)

FIGURE 10. (Up) High-resolution luminescence speleothem record of solar insolation at about 1000 y B P from Cold WaterCave, Iowa. This speleothem sample has been dated by 9 TIMS U/Th ages [14]. (Down) Cycles presented in the record. The

presence of a 27- day cycle of solar rotation suggests modulation of the transparency of the atmosphere by solar wind modulationof the cosmic rays flux.

4. GALACTIC COSMIC RAYS FLUX AMPLIFICATION OFTHE SOLAR IMPACT ON CLIMATE

Cosmic rays may serve as nucleation centers for condensation of the water in the clouds8. The galactic Cosmic RaysFlux at the Earth is strongly modulated by the solar wind [30]. Stronger solar wind produces a lower cosmic raysflux and may result in less cloud cover. Solar luminosity variations correlate with the solar wind strength. Theweaker cloud cover produces higher sky transparency and higher solar insolation at the Earths surface, and viceversa. The cosmic rays-cloud cover mechanism thus may multiply impacts of solar irradiance variation on the

insolation at the Earths surface. Therefore this effect should produce a strong positive correlation between the solaractivity (especially solar irradiance variations) and global temperatures. In many cases this is observed despite the

very small variations of solar irradiance [31].We used Real Space periodogramme analysis to calculate the intensity of cycles of speleothem luminescence

(representing cycles of solar radiation or air temperature) in a high-resolution composite record from Savi Cave near

Trieste, Italy [32] and a speleothem from Rats Nest Cave, Alberta [33]. The power spectra demonstrate that thesespeleothems recorded cycles of the soil temperature with durations of about 11 and 22 years. The 11-year solar cycleproduces variations of the solar constant with amplitude of less than 0.4% [2]. Cosmic rays influence on the

atmospheric transparency provides a mechanism of strong multiplication of solar variations on the solar radiation atthe Earths surface. Luminescence of speleothems from Rats Nest Cave, Alberta, reproduce paleo air temperatures[15], but records from this cave exhibit a strong cycle of 425 years, which is an important solar cycle [34]. Thiscycle probably modulates air temperature in addition to the cosmic rays flux recorded by

14C variations. The same

records also contain centennial and bi-centennial solar cycles.We found that the cycle of 11 500 years produce variations of +/3.6 % of the solar insolation in our records

(Table 1). If the cosmic rays mechanism is added, this variation can be produced by much smaller variations of

actual solar luminosity. This most powerful solar cycle is as intensive as most of the Milankovitch cycles and canproduce climatic variations with intensity comparable to that of the orbital variations. Known decadal and even

century solar cycles have negligible intensity (100 times less intensive) relative to this cycle.

0

0.0001

0.0002

0.0003

0.0004

0.0005

0.0006

0 5 10 15 20 25 30 35 40 45 50

days

lg(I)

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In addition to the annual cycle produced by the Earths rotation we found a sub- annual cycle with duration of 27

days in a high- resolution luminescent record from Cold Water Cave, Iowa (Fig. 10). Such cycles can be producedby the period of rotation of the Sun, which causes similar variations in the solar wind (Figs. 2 and 3) modulations ofthe cosmic rays flux. The rotation leads to the periodic appearance of the same active zones on the visible solar

surface. They are major emitters of solar wind, so produce strong 27-days variations in its density (Figs. 2 and 3).Thus solar wind modulation of cosmic rays flux may cause strong amplification of the weak variations of the solarconstant (Fig. 4) to produce measurable variations of the soil temperature measured in a ground luminescence record

(Fig. 10).The integrated sky transparency may vary with up to 25% between clearest and cloudiest days [35], but if

integrated over one year this variation is less then 0.65% from year to year if a normal distribution of sunny days isassumed. In fact even lower variations should be expected. This suggests that cosmic rays modulation of the climatecan be more significant during short periods, especially those produced by the solar rotation.

Svensmark and FriisChristensen [8] measured variations in the cloud cover of 3% during an average 11-yr.solar cycle and estimated that this caused variation of the insolation of 0.81.7 Wm2. Such variation is able toproduce significant climatic variation.

5. CONCLUSIONS

An 11500- year cycle was found previously to be the most intensive cycle in the 14

C calibration record and wasinterpreted to be of geomagnetic origin [26]. Our studies suggest that this is a solar cycle modulating the geomagne-tic field and cosmic rays flux.

We determined the solar origin of other strong cycles with durations of 11 500, 4400, 3950, 2770, 2500, 2300,

2090, 1960, 1670, 1460, 1280, 1195, 1145, 1034, 935, 835, 814, 775, 750, 660, 610, 550, and 538 years and of manyweak cycles with duration from one to five centuries. The main variations in the

14C and geomagnetic field records

are produced by the solar wind. Known decadal and even centennial solar cycles have negligible intensity relative tothese cycles. These millennial solar luminosity cycles can produce climatic variations with intensity comparable tothat of the orbital variations.

We determined that the 11 500 year solar cycle is about 100 times more intensive than the observed cycles in sunspots.

Solar luminosity and orbital variations both cause variations of solar insolation affecting the climate by the same

mechanism. During the last 60 000 years intensity of solar irradiance variations has prevailed over the orbital effects,however.

Solar wind cycles can affect Earths climate due to modulation of the Cosmic rays flux. Cosmic raysamplification of solar variations by changing the transparency of the air become important at durations shorter than11 yrs and may be most significant in timescales less than one year.

REFERENCES

1. E. Friis-Christensen, Solar-Terrestrial Connection: Long-Term and Short-Term Climate Variability in Encyclopedia ofAstronomy and Astrophysics, edited by P. Murdin, Institute of Physics Publishing, Nature Publishing Group, London, 2001,pp. 43304334.

2. J. R. Hickey, B. M. Alton, F. J. Griffin, H. Jacobowitz, P. Pellegrino, E. A. Smith,; T. H. Vonder, and R. H. Maschhoff,

Solar Variability Indications fromNIMBUS 7Satellite Data in Variations of the Solar Constant, edited by S. Sofia, NASA-CP-2191, 1981, pp.5972.

3. I. Veklich, Problems of Paleoclimatology, Naukova Dumka, Kiev, 1987 (in Russian).4. Y. Y. Shopov, Speleothem Records of Environmental Changes in the Past in Karst Processes and the Carbon Cycle, edited

byY. Daoxian and Z. Cheng, Geological Publishing House, IGCP379, Beijing, 2002, pp. 121135.5. Y. Y. Shopov,Int. J. Speleology,33, 1924 (2004).

6. T. J. Crowley, Science289, 270277 (2000).7. G. Ohring and P. F. Clapp,J. Atmos. Sci.37, 447454 (1980).8. H. Svensmark and E. Friis-Christensen,J. Atmos. Sol. Terr. Phys.59, 12251232 (1997).

9. OMNI (2010) Goddard Space Flight Center, Space Physics Data Facility, OMNIWEB, DATA & ORBITS,http://omniweb.gsfc.nasa.gov/ow_min.html .

10.J. King and N. Papitashvili (2010) One min and 5-min solar wind data sets at the Earth's bow shock nose,

http://omniweb.gsfc.nasa.gov/html/omni_min_data.html#6 .11.Yu. I. Vitinsky, Solar Activity, Nauka, Moscow, 1983 (in Russian).

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Cycles of the Solar Wind Flux at the Front of the Earth’s Magnetosphere