Long-Term Space WeatherLong-Term Space Weatherandand

Terrestrial ClimateTerrestrial Climate

David H. HathawayDavid H. Hathaway

NASA/MSFCNASA/MSFC

National Space Science and Technology CenterNational Space Science and Technology Center

Huntsville, ALHuntsville, AL

2004 December 172004 December 17

OutlineOutline

• Space Weather – What is it?Space Weather – What is it?

• Sunspots and the Sunspot CycleSunspots and the Sunspot Cycle

• Long Term Changes in Space WeatherLong Term Changes in Space Weather

• Space Weather and Terrestrial ClimateSpace Weather and Terrestrial Climate

Solar Activity – The Bastille Day EventSolar Activity – The Bastille Day Event

Effects of Solar Activity:Effects of Solar Activity:On SatellitesOn Satellites

Radiation (protons, electrons, alpha particles) from solar flares and Radiation (protons, electrons, alpha particles) from solar flares and coronal mass ejections can damage electronics on satellites. Heating coronal mass ejections can damage electronics on satellites. Heating of the Earth’s upper atmosphere increases satellite drag.of the Earth’s upper atmosphere increases satellite drag.

•1991 GOES1991 GOES•1995 Deutsche Telekom1995 Deutsche Telekom•1996 Telesat Canada1996 Telesat Canada•1997 Telstar 4011997 Telstar 401•2000/07/14 ASCA2000/07/14 ASCA•2003 Mars Odyssey2003 Mars Odyssey

•4500 spacecraft 4500 spacecraft anomalies over last 25 anomalies over last 25 yearsyears

Effects of Solar Activity:Effects of Solar Activity:On Power GridsOn Power Grids

Solar disturbances shake the Earth’s magnetic field. This sets up Solar disturbances shake the Earth’s magnetic field. This sets up huge electrical currents in power lines and pipe lines. huge electrical currents in power lines and pipe lines.

The solar storm of March 13The solar storm of March 13thth 1989 fried a $10M transformer in NJ. 1989 fried a $10M transformer in NJ. The same storm interrupted power to the province of Quebec for 6 The same storm interrupted power to the province of Quebec for 6 days.days.

Effects of Solar Activity:Effects of Solar Activity:On Radio Wave PropagationOn Radio Wave Propagation

Variations in ionizing radiation (UV, EUV, X-rays) from the Sun Variations in ionizing radiation (UV, EUV, X-rays) from the Sun alter the ionosphere – changing the Maximum Usable Frequency alter the ionosphere – changing the Maximum Usable Frequency for high frequency radio communications and altering position for high frequency radio communications and altering position information for GPS systems.information for GPS systems.

Sunspots and Solar RotationSunspots and Solar Rotation

Sunspots and Magnetic FieldsSunspots and Magnetic Fields

International Sunspot Number – devised by Rudolf Wolf in the 1850sInternational Sunspot Number – devised by Rudolf Wolf in the 1850s(1749-Present but incomplete before 1850)(1749-Present but incomplete before 1850)

SSN = 10 G + N SSN = 10 G + N (G = # of Groups, N = # of spots)(G = # of Groups, N = # of spots)

Group Sunspot Number – devised by Hoyt and Schatten in the 1990sGroup Sunspot Number – devised by Hoyt and Schatten in the 1990s(1610-Present more complete than Wolf’s sunspot number)(1610-Present more complete than Wolf’s sunspot number)

GSSN = 12.08 GGSSN = 12.08 G

Sunspot numbers are also generated by NOAA in Boulder, CO and bySunspot numbers are also generated by NOAA in Boulder, CO and bythe American Association of Variable Star Observersthe American Association of Variable Star Observers

Sunspot NumberSunspot Number

The “11-year” Sunspot CycleThe “11-year” Sunspot Cycle

Cycle periods are normally distributed with a mean period of 131 months Cycle periods are normally distributed with a mean period of 131 months and a standard deviation of 14 months.and a standard deviation of 14 months.

Sunspot AreaSunspot Area 10.7cm Radio Flux10.7cm Radio Flux GOES X-Ray FlaresGOES X-Ray Flares

Climax Cosmic-Ray FluxClimax Cosmic-Ray Flux

Sunspot number is well correlated with other measures of solar activity. The Sunspot number is well correlated with other measures of solar activity. The long record of sunspot numbers helps to characterize the solar cycle.long record of sunspot numbers helps to characterize the solar cycle.

Sunspot Number and Solar ActivitySunspot Number and Solar Activity

Geomagnetic aa indexGeomagnetic aa indexTotal IrradianceTotal Irradiance

The Waldmeier EffectThe Waldmeier EffectThe sunspot cycles are asymmetric – the time to rise to maximum is The sunspot cycles are asymmetric – the time to rise to maximum is less than the time to fall to minimum. Furthermore, large cycles take less than the time to fall to minimum. Furthermore, large cycles take less time to reach maximum than do small cycles.less time to reach maximum than do small cycles.

Amplitude-Period EffectAmplitude-Period EffectThe amplitude of a cycle is anti-correlated to the period of the The amplitude of a cycle is anti-correlated to the period of the previousprevious cycle. Large cycles follow short cycles. cycle. Large cycles follow short cycles.

Amplitude-Minimum EffectAmplitude-Minimum EffectThe amplitude of a cycle is correlated with the size of the minimum The amplitude of a cycle is correlated with the size of the minimum that precedes the cycle.that precedes the cycle.

Individual Cycle CharacteristicsIndividual Cycle Characteristics

Big cycles start early and grow fast. Big cycles start early and grow fast. This directly This directly produces the Waldmeier Effect. By doing so they cut produces the Waldmeier Effect. By doing so they cut short the previous cycle (Amplitude-Period Effect) short the previous cycle (Amplitude-Period Effect) and produce a higher minimum due to the overlap and produce a higher minimum due to the overlap (Amplitude-Minimum Effect).(Amplitude-Minimum Effect).

PredictionPrediction

Understanding the Sunspot Cycle:Understanding the Sunspot Cycle:Solar MagnetismSolar Magnetism

The polarity of the preceding spots in the northern hemisphere is The polarity of the preceding spots in the northern hemisphere is opposite to the polarity of the preceding spots in the southern opposite to the polarity of the preceding spots in the southern hemisphere. The polarities reverse from one cycle to the next.hemisphere. The polarities reverse from one cycle to the next.

Hale’s Polarity LawHale’s Polarity Law

Sunspot Latitude DriftSunspot Latitude Drift

Sunspots appear in two bands on either side of the equator. These Sunspots appear in two bands on either side of the equator. These bands spread in latitude and then migrate toward the equator as the bands spread in latitude and then migrate toward the equator as the cycle progresses. Cycles often overlap around the time of minimum.cycle progresses. Cycles often overlap around the time of minimum.

The Sun’s Magnetic CycleThe Sun’s Magnetic CycleThis movie shows the equatorward drift of the active regions and This movie shows the equatorward drift of the active regions and Hale’s polarity law. It also reveals the differential rotation (faster Hale’s polarity law. It also reveals the differential rotation (faster at the equator, slower at high latitudes) and poleward meridional at the equator, slower at high latitudes) and poleward meridional flow.flow.

Polar Field Reversal at Cycle MaximumPolar Field Reversal at Cycle Maximum

The polarity of the polar magnetic fields reverses at about the time of the The polarity of the polar magnetic fields reverses at about the time of the solar activity maximum. solar activity maximum.

Active Region Tilt: Joy’s LawActive Region Tilt: Joy’s Law

Active regions are tilted so that the following polarity spots are Active regions are tilted so that the following polarity spots are slightly poleward of the preceding polarity spots. This tilt slightly poleward of the preceding polarity spots. This tilt increases with latitude.increases with latitude.

Howard, R.F., Solar Phys. 136, 251-262 (1991)

Understanding the Sunspot Cycle:Understanding the Sunspot Cycle:Dynamo TheoryDynamo Theory

The The ΩΩ-effect-effect

The The αα-effect-effect

Convection Zone FlowsConvection Zone FlowsHelioseismology finds a rapidly Helioseismology finds a rapidly rotating equator with radial shear rotating equator with radial shear in layers at the top and bottom of in layers at the top and bottom of the convection zone along with a the convection zone along with a poleward meridional flow in the poleward meridional flow in the outer convection zone.outer convection zone.

Dynamos with Meridional FlowDynamos with Meridional FlowDynamo models that incorporate a deep meridional flow to Dynamo models that incorporate a deep meridional flow to transport magnetic flux toward the equator at the base of the transport magnetic flux toward the equator at the base of the convection zone appear promising. The current cycle period and convection zone appear promising. The current cycle period and the strength of the N+2 cycle are inversely proportional to the the strength of the N+2 cycle are inversely proportional to the meridional flow speed. meridional flow speed.

Dikpati and Charbonneau, Dikpati and Charbonneau, ApJApJ 518, 508-520, 1999 518, 508-520, 1999 Per ~Per ~ V V-1-1 αα-1/7-1/7 ηη1/41/4

We examined the latitude We examined the latitude drift of the sunspot zones by drift of the sunspot zones by first separating the cycles first separating the cycles where they overlap at where they overlap at minimum.minimum.

We then calculated the We then calculated the centroid position of the daily centroid position of the daily sunspot area averaged over sunspot area averaged over solar rotations for each solar rotations for each hemisphere.hemisphere.

[Hathaway, Nandy, Wilson, & Reichmann, [Hathaway, Nandy, Wilson, & Reichmann, ApJApJ 589. 665-670 2003 & 589. 665-670 2003 & ApJApJ 602, 543-543 602, 543-543 2004]2004]

Latitude Drift of Sunspot ZonesLatitude Drift of Sunspot Zones

The drift rate in each hemisphere and for each cycle (with one The drift rate in each hemisphere and for each cycle (with one exception) slows as the activity approaches the equator. This exception) slows as the activity approaches the equator. This behavior is expected from dynamo models with deep meridional behavior is expected from dynamo models with deep meridional flow. flow.

Drift Rate vs. LatitudeDrift Rate vs. Latitude

The sunspot cycle period is anti-correlated with the drift velocity The sunspot cycle period is anti-correlated with the drift velocity at cycle maximum. The faster the drift rate the shorter the period. at cycle maximum. The faster the drift rate the shorter the period. This is also expected from dynamo models with deep meridional This is also expected from dynamo models with deep meridional flow.flow.

R=-0.595% Significant

Drift Rate – Period Anti-correlationDrift Rate – Period Anti-correlation

The drift velocity at cycle maximum is The drift velocity at cycle maximum is positivelypositively correlated with correlated with the amplitude of the second following (N+2) cycle. This is the amplitude of the second following (N+2) cycle. This is contrary to the prediction by dynamo models with deep contrary to the prediction by dynamo models with deep meridional flow but it does provide a prediction for the meridional flow but it does provide a prediction for the amplitudes of future cycles.amplitudes of future cycles.

R=0.7R=0.799% Significant99% Significant

Drift Rate – Amplitude CorrelationsDrift Rate – Amplitude Correlations

The Group Sunspot Number of Hoyt and Schatten closely follows The Group Sunspot Number of Hoyt and Schatten closely follows the International Sunspot number as well as other indicators of the International Sunspot number as well as other indicators of solar activity. It has the advantage of extending back in time solar activity. It has the advantage of extending back in time through the Maunder Minimum to 1610.through the Maunder Minimum to 1610.

Long-Term VariabilityLong-Term Variability

MaunderMaunderMinimumMinimum

Secular Trend Since Maunder MinimumSecular Trend Since Maunder MinimumThe Group Sunspot Number shows a significant secular increase The Group Sunspot Number shows a significant secular increase in cycle amplitude since the Maunder Minimum.in cycle amplitude since the Maunder Minimum.

DaltonMinimum

Multi-Cycle Periodicities?Multi-Cycle Periodicities?After removing the secular trend, there is little evidence for any After removing the secular trend, there is little evidence for any significant periodic behavior with periods of 2-cycles significant periodic behavior with periods of 2-cycles (Gnevyshev-Ohl) or 3-cycles (Ahluwalia) There is some evidence (Gnevyshev-Ohl) or 3-cycles (Ahluwalia) There is some evidence for periodic behavior with a period of about 9-cycles for periodic behavior with a period of about 9-cycles (Gleissberg). (Gleissberg).

Longer-Term Variations:Longer-Term Variations:The Radio Isotope StoryThe Radio Isotope Story

The complex magnetic structures in the solar wind at the time of The complex magnetic structures in the solar wind at the time of solar activity maximum scatter galactic cosmic rays out of the solar activity maximum scatter galactic cosmic rays out of the solar system. This decreases the production of radio isotopes solar system. This decreases the production of radio isotopes such as such as 1414C and C and 1010Be. (The strongest anti-correlation is obtained Be. (The strongest anti-correlation is obtained with an 8-month time lag – the time it takes for the solar wind to with an 8-month time lag – the time it takes for the solar wind to travel ~ 60 AU.)travel ~ 60 AU.)

1414C pre-industrial distributionC pre-industrial distribution

Atmosphere & Biosphere

Geo/heliomagnetic modulation of

14C production rate

Ocean mixed layerOcean mixed layer

Diffusive deep ocean Diffusive deep ocean

1414C activity C activity in reservoirin reservoir

100%100%

95%95%

~85%~85%

Carbon fraction Carbon fraction in reservoirin reservoir

3%3%

2%2%

95%95%

7 yrs7 yrs

centuriescenturies

Galactic cosmic ray fluxGalactic cosmic ray flux

Earth magnetic field

Solar wind magnetic field

TroposphereTroposphere

1414N N 1414C, C, 1414COCO2 2 (T(T½½ : 5730 yr) : 5730 yr)

Slide Source: Bernd KromerSlide Source: Bernd Kromer

1600 1700 1800 1900

30

20

10

0

-10

-201600 1650 1700 1750 1800 1850 1900

0

50

100

150

200

250

300

single-year 14C 15-year running mean

DaltonMin.

MaunderMinimum

14C

inverted

SSN

14C

AD

sunspot number

1600 1700 1800 1900

0

50

100

150

200

250

300

1414C Fluctuations Compared to SSNC Fluctuations Compared to SSN

http://depts.washington.edu/qil/datasets/http://depts.washington.edu/qil/datasets/Stuiver et al, The Holocene, 1993Stuiver et al, The Holocene, 1993

0

100

200

300

1600 1620 1640 1660 1680 1700 1720 1740Year AD

13.5-15.5yrs 13.5-15.5yrs (14.4yrs)(14.4yrs)

0.200.20

0.160.16

0.120.12

0.080.08

0.040.04Fre

qu

ency

(1/

yr)

Fre

qu

ency

(1/

yr)

The Solar Cycle:The Solar Cycle:Through the Maunder MinimumThrough the Maunder Minimum

SS

NS

SN

The solar cycle continued (without spots) through the Maunder The solar cycle continued (without spots) through the Maunder Minimum but with a longer period (Minimum but with a longer period (ΔΔ1414C results).C results).

Solar Activity over last 11,400 YearsSolar Activity over last 11,400 Years

Solanki Solanki et al.et al., , NatureNature 431 1084-1087 (2004) have reconstructed 431 1084-1087 (2004) have reconstructed the sunspot number over the last 11,400 years using the sunspot number over the last 11,400 years using 1414C data. C data. Comparisons with the observed Group Sunspot Numbers (GSN) Comparisons with the observed Group Sunspot Numbers (GSN) and sunspot numbers reconstructed from and sunspot numbers reconstructed from 1010Be ice core data Be ice core data show good agreement. They conclude that the high levels of show good agreement. They conclude that the high levels of solar activity seen in the last 60 years have not been seen for solar activity seen in the last 60 years have not been seen for 8000 years. (Note, however, that this high level of activity is seen 8000 years. (Note, however, that this high level of activity is seen only in actual sunspot number.)only in actual sunspot number.)

Independent Independent 1010Be ReconstructionsBe Reconstructions

Solanki Solanki et al.et al. 2004 2004 Caballero-Lopez Caballero-Lopez et al.et al. in press. in press.

Independent reconstructions of Sunspot Number (Solanki et al. Independent reconstructions of Sunspot Number (Solanki et al. 2004) and Interplanetary Magnetic Field (Caballero-Lopez, Moraal, 2004) and Interplanetary Magnetic Field (Caballero-Lopez, Moraal, McCracken, and McDonald in press) show nearly identical McCracken, and McDonald in press) show nearly identical behavior – giving further confidence to the results. behavior – giving further confidence to the results.

Further characterizations of the solar activity cycle from these Further characterizations of the solar activity cycle from these data are underway.data are underway.

The Solar Activity-Climate ConnectionThe Solar Activity-Climate Connection

Changes in the Earth’s climate (long-term temperature) appear to Changes in the Earth’s climate (long-term temperature) appear to be connected to solar activity, both show similar variations.be connected to solar activity, both show similar variations.

The Northern Hemisphere TemperatureThe Northern Hemisphere Temperatureand Solar Cycle Controversyand Solar Cycle Controversy

Yearly Sunspot Numbers and Reconstructed Northern Hemis-Yearly Sunspot Numbers and Reconstructed Northern Hemis-phere Temperature (Mann, Bradley & Hughesphere Temperature (Mann, Bradley & Hughes Nature Nature 392, 779- 392, 779-787, 1998) smoothed with an 11-year FWHM tapered Gaussian 787, 1998) smoothed with an 11-year FWHM tapered Gaussian and trimmed to valid smoothed data. The correlation coefficient and trimmed to valid smoothed data. The correlation coefficient from the overlapping period is 0.78.from the overlapping period is 0.78.

The Friis-Christensen and Larsen (1991) study has been The Friis-Christensen and Larsen (1991) study has been questioned on two points – 1) cycle length is poorly correlated questioned on two points – 1) cycle length is poorly correlated with activity and 2) the method of smoothing and then using end with activity and 2) the method of smoothing and then using end points improperly smoothed compromises the recent data points.points improperly smoothed compromises the recent data points.

Longer-Term Variations:Longer-Term Variations:Grand Maxima and MinimaGrand Maxima and Minima

Measurements of the variations in Measurements of the variations in 1414C in tree rings from what C in tree rings from what would be expected from constant production/decay rates shows would be expected from constant production/decay rates shows deep minima and high maxima in solar activity over century and deep minima and high maxima in solar activity over century and millennia time scales.millennia time scales.

Link to North-Atlantic CoolingLink to North-Atlantic CoolingIce rafted debris found in North Atlantic sediment is used as an Ice rafted debris found in North Atlantic sediment is used as an indicator of temperature (more debris – cooler temperatures). indicator of temperature (more debris – cooler temperatures). Bond et al. 2001 Bond et al. 2001 ScienceScience 294, 2130 find good correlation with 294, 2130 find good correlation with 14C production.14C production.

Possible MechanismsPossible Mechanisms

Solar Irradiance VariationsSolar Irradiance Variations Cosmic Ray “Cloud Seeding”Cosmic Ray “Cloud Seeding”

A brighter Sun at solar A brighter Sun at solar activity maxima could make activity maxima could make the climate warmer.the climate warmer.

Fewer clouds at solar activity Fewer clouds at solar activity maxima could make the maxima could make the climate warmer.climate warmer.

Total Solar Irradiance MeasurementsTotal Solar Irradiance MeasurementsSeven different TSI radio-meters have been used, with offsets.Seven different TSI radio-meters have been used, with offsets.The trend in the composite depends on the introduced corrections.The trend in the composite depends on the introduced corrections.

Iq(μ,) quiet Sun intensity

(Fontenla et al. 1993; 0 FP)

A 4-component Irradiance ModelA 4-component Irradiance Modelwith 1 Free Parameterwith 1 Free Parameter

u(t) filling factor of umbra

p(t) filling factor of penumbra

(MDI continuum; 0 FP)

If (μ,) facular intensity

(modified P-model; 0 FP; Fontenla et al. 1993; Unruh et al. 2000)

f (t) filling factor of faculae

(MDI magnetograms; 1 FP)

Iu(μ,) spot umbral intensity

I

p(μ,) spot penumbral intensity

(cool Kurucz models; 0 FP)

IIrradiance during cycle 23 From Modelrradiance during cycle 23 From Model

Krivova et al. 2003 A&A Lett

Solar Spectral VariabilitySolar Spectral VariabilityThe 0.1% variations in the visible and IR are probably too small to The 0.1% variations in the visible and IR are probably too small to produce the observed variations.produce the observed variations. While the solar irradiance at While the solar irradiance at wavelengths shorter than 300 nm is weak, it is highly variable wavelengths shorter than 300 nm is weak, it is highly variable over the solar cycle (3% @ 300 nm to 100% @ 100 nm). This over the solar cycle (3% @ 300 nm to 100% @ 100 nm). This should produce changes in stratospheric chemistry.should produce changes in stratospheric chemistry.

Cosmic Rays and Cloud CoverCosmic Rays and Cloud Cover

Correlations have been found between cloud cover and cosmic Correlations have been found between cloud cover and cosmic rays (Svensmark and Friis-Christensen, 1997) and between rays (Svensmark and Friis-Christensen, 1997) and between stratospheric aerosols and cosmic rays (Vanhellemont, Fussen, stratospheric aerosols and cosmic rays (Vanhellemont, Fussen, and Bingen, 2002).and Bingen, 2002).

ConclusionsConclusions

• Solar activity varies on a wide range of time Solar activity varies on a wide range of time scales from milli-seconds to millennia.scales from milli-seconds to millennia.

• Similarities in the records for solar activity and Similarities in the records for solar activity and terrestrial climate strongly suggest a link terrestrial climate strongly suggest a link between the two.between the two.

•The mechanism by which solar activity The mechanism by which solar activity influences climate is uncertain.influences climate is uncertain.

ResourcesResources

• Hoyt, D. V. and Schatten, K. H., 1997. Hoyt, D. V. and Schatten, K. H., 1997. The Role of the Sun in The Role of the Sun in Climate ChangeClimate Change, Oxford University Press, Oxford, 279 pp., Oxford University Press, Oxford, 279 pp.

• Soon, W. W-H and Yaskell, S. H., 2003. Soon, W. W-H and Yaskell, S. H., 2003. The Maunder Minimum The Maunder Minimum and the Variable Sun-Earth Connectionand the Variable Sun-Earth Connection, World Scientific , World Scientific Publishing, Singapore, 278 pp.Publishing, Singapore, 278 pp.

• Friis-Christensen, E. and Lassen, K., 1991. Friis-Christensen, E. and Lassen, K., 1991. ScienceScience 254, 698-700. 254, 698-700.

• Reid, G. C., 1991. Reid, G. C., 1991. J. Geophys. Res.J. Geophys. Res. 96, 2835-2844. 96, 2835-2844.

• Bond et al., 2001. Bond et al., 2001. ScienceScience 294, 2130-2136. 294, 2130-2136.

•Vanhellemont, F., Fussen, D., and Bingen, C., 2002. Vanhellemont, F., Fussen, D., and Bingen, C., 2002. Geophys. Geophys. Res. Lett. Res. Lett. 29 No. 15, 1715-1718.29 No. 15, 1715-1718.

•Solanki, S. et al., 2004. Solanki, S. et al., 2004. NatureNature 431, 1084-1087. 431, 1084-1087.