Solar Cycle UpdateSolar Cycle Update

Dr. David H. HathawayDr. David H. Hathaway

NASA/NSSTCNASA/NSSTC

Huntsville Hamfest 2007 August 18Huntsville Hamfest 2007 August 18

OutlineOutline

• Significance of the Solar CycleSignificance of the Solar Cycle• Characteristics of the Sunspot CycleCharacteristics of the Sunspot Cycle• Characteristics of the Magnetic CycleCharacteristics of the Magnetic Cycle• Predictions for Solar Cycle 24Predictions for Solar Cycle 24• ConclusionsConclusions

Significance of the Solar CycleSignificance of the Solar Cycle

Solar Activity: The Bastille Day EventSolar Activity: The Bastille Day Event

Solar activity (including: flares, prominence eruptions, coronal Solar activity (including: flares, prominence eruptions, coronal mass ejections, solar energetic particle events, and high-speed mass ejections, solar energetic particle events, and high-speed solar wind streams from coronal holes) varies in frequency with the solar wind streams from coronal holes) varies in frequency with the solar cycle.solar cycle.

A Prominence EruptionA Prominence Eruption

Coronal Mass EjectionsCoronal Mass Ejections

From the Sun to the EarthFrom the Sun to the Earth

Solar Activity Affects…

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. coronal mass ejections can damage electronics on satellites. Heating of the Earth’s upper atmosphere increases satellite drag.Heating 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.

HF Communication only

• Polar flights departing from North America use VHF (30-300 MHz) comm or Polar flights departing from North America use VHF (30-300 MHz) comm or Satcom with Canadian ATCs and Arctic Radio.Satcom with Canadian ATCs and Arctic Radio.

• Flights rely on HF (3 – 30 MHz) communication inside the 82 degree circle.Flights rely on HF (3 – 30 MHz) communication inside the 82 degree circle.

• Growth: Airlines operating China-US routes goes from 4 to 6 and then Growth: Airlines operating China-US routes goes from 4 to 6 and then number of weekly flights goes from 54 to 249 over the next 6-years.number of weekly flights goes from 54 to 249 over the next 6-years.

Effects of Solar Activity:Effects of Solar Activity:On Airline OperationsOn Airline Operations

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.

Effects of Solar Activity:Effects of Solar Activity:On Climate?On Climate?

Characteristics of the Sunspot CycleCharacteristics of the Sunspot Cycle

Sunspot number is well correlated with solar activity. The 400-Sunspot number is well correlated with solar activity. The 400-year length of the sunspot number record helps to characterize year length of the sunspot number record helps to characterize the solar cycle. The connection with cosmic rays leaves even the solar cycle. The connection with cosmic rays leaves even longer records of solar activity in tree rings (longer records of solar activity in tree rings (1414C) and ice cores C) and ice cores ((1010Be).Be).

Sunspot Number and Solar ActivitySunspot Number and Solar Activity

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

Climax Cosmic-Ray FluxClimax Cosmic-Ray FluxGeomagnetic aa indexGeomagnetic aa indexTotal IrradianceTotal Irradiance

[Schwabe, 1844][Schwabe, 1844]Heinrich Schwabe, a Swiss apothecary, reported a cycle of about 10-Heinrich Schwabe, a Swiss apothecary, reported a cycle of about 10-years length in the number of sunspot groups and spotless days from years length in the number of sunspot groups and spotless days from 18 years of his own observations. Rudolf Wolf then initiated daily 18 years of his own observations. Rudolf Wolf then initiated daily counts of sunspots and attempted to extend the count back to 1749.counts of sunspots and attempted to extend the count back to 1749.

The 11-year Sunspot or Wolf CycleThe 11-year Sunspot or Wolf Cycle

The Shape of the Solar CycleThe Shape of the Solar CycleThe sunspot cycles are asymmetric in shape with rapid rises to The sunspot cycles are asymmetric in shape with rapid rises to maximum and slower declines to minimum. Bigger cycles take less maximum and slower declines to minimum. Bigger cycles take less time to reach maximum than do smaller cycles (The Waldmeier time to reach maximum than do smaller cycles (The Waldmeier Effect). Cycle periods have been normally distributed about a Effect). Cycle periods have been normally distributed about a mean of about 131 months.mean of about 131 months.

Sunspot Latitude Drift – SpSunspot Latitude Drift – Spoeoerer’s Lawrer’s Law[Carrington, 1858][Carrington, 1858]

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

The Maunder MinimumThe Maunder Minimum

Sunspot cycles vary widely in amplitude with occasional periods Sunspot cycles vary widely in amplitude with occasional periods of inactivity like the Maunder Minimum (1645-1715).of inactivity like the Maunder Minimum (1645-1715).

[Maunder, 1894][Maunder, 1894]

DaltonMinimum

Multi-Cycle VariabilityMulti-Cycle VariabilityAfter 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 (Gnevyshev-significant periodic behavior with periods of 2-cycles (Gnevyshev-Ohl) or 3-cycles (Ahluwalia), and only weak evidence for variability Ohl) or 3-cycles (Ahluwalia), and only weak evidence for variability over 7- to 10-cycles (Gleissberg).over 7- to 10-cycles (Gleissberg).

Short-Term VariabilityShort-Term VariabilityA number of short-term periodicities have been reported for solar A number of short-term periodicities have been reported for solar activity. In most, if not all cases, the period and the phase of the activity. In most, if not all cases, the period and the phase of the oscillations vary with time.oscillations vary with time.

Empirical Mode DecompositionEmpirical Mode Decomposition

Monthly sunspot numbersMonthly sunspot numbers

Decadal time scale variationsDecadal time scale variations(The solar cycle)(The solar cycle)

Bi-annual/Annual time scale variationsBi-annual/Annual time scale variations(Double peaks for some cycles depending on phase)(Double peaks for some cycles depending on phase)

Annual/Semi-annual time scale variationsAnnual/Semi-annual time scale variations(152d periodicity from 1980 to mid-1983)(152d periodicity from 1980 to mid-1983)

Monthly time scale variationsMonthly time scale variations(Largely noise)(Largely noise)

20 21 2220 21 22

Hemispheric DifferencesHemispheric DifferencesThe hemispheres display distinct asymmetries (North - South) that The hemispheres display distinct asymmetries (North - South) that are evident in a variety of indicators. Yet, both hemispheres are are evident in a variety of indicators. Yet, both hemispheres are more-or-less locked in phase.more-or-less locked in phase.

Magnetic Cycle CharacteristicsMagnetic Cycle Characteristics

Solar Magnetism

Active Region Tilt: Joy’s LawActive Region Tilt: Joy’s Law[Hale [Hale et al.,et al., 1919] 1919]

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

Howard (1991)Howard (1991)

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[Hale [Hale et al.,et al., 1919] 1919]

Cycle 22Cycle 221989/08/021989/08/02

Cycle 23Cycle 232000/06/262000/06/26

Magnetic field erupts through the surface as tilted bipoles in two Magnetic field erupts through the surface as tilted bipoles in two bands on either side of the equator. Individual regions decay by bands on either side of the equator. Individual regions decay by spreading out over the surface. Remnant magnetic elements are spreading out over the surface. Remnant magnetic elements are sheared apart by differential rotation and carried poleward by a sheared apart by differential rotation and carried poleward by a meridional flow.meridional flow.

The Sun’s Magnetic CycleThe Sun’s Magnetic Cycle

Polar Field ReversalsPolar Field Reversals

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

[Babcock, 1959][Babcock, 1959]

In/CCWIn/CCW

Out/CWOut/CW

Dikpati & Charbonneau DynamoDikpati & Charbonneau Dynamo

This is a 2D kinematic dynamo which uses the observed internal This is a 2D kinematic dynamo which uses the observed internal differential rotation, a realistic meridional circulation, a reasonable differential rotation, a realistic meridional circulation, a reasonable diffusivity, and a parameterized diffusivity, and a parameterized αα-effect. It produces a reversing -effect. It produces a reversing magnetic field configuration with a 22-year period and an equator-magnetic field configuration with a 22-year period and an equator-ward propagation of active zones.ward propagation of active zones.

Solar Cycle PredictionsSolar Cycle Predictions

Dikpati, de Toma & Gilman (2006) have fed sunspot areas and Dikpati, de Toma & Gilman (2006) have fed sunspot areas and positions into their numerical model for the Sun’s dynamo and positions into their numerical model for the Sun’s dynamo and reproduced the amplitudes of the last eight cycles with unprecedented reproduced the amplitudes of the last eight cycles with unprecedented accuracy (RMS error < 10). Recent results for each hemisphere shows accuracy (RMS error < 10). Recent results for each hemisphere shows similar accuracy.similar accuracy.

Cycle 24 Prediction ~ 160 Cycle 24 Prediction ~ 160 ± 15± 15

A Dynamo PredictionA Dynamo Prediction

Precursor PredictionsPrecursor Predictions

Precursor techniques use aspects of the Sun and solar activity prior Precursor techniques use aspects of the Sun and solar activity prior to the start of a cycle to predict the size of the next cycle. The two to the start of a cycle to predict the size of the next cycle. The two leading contenders are: 1) geomagnetic activity from high-speed leading contenders are: 1) geomagnetic activity from high-speed solar wind streams prior to cycle minimum and 2) polar field strength solar wind streams prior to cycle minimum and 2) polar field strength near cycle minimum.near cycle minimum.

Geomagnetic Prediction ~ 160 Geomagnetic Prediction ~ 160 ± 25± 25(Hathaway & Wilson 2006)(Hathaway & Wilson 2006)

Polar Field Prediction ~ 75 Polar Field Prediction ~ 75 ± 8± 8(Svalgaard, Cliver, Kamide 2005)(Svalgaard, Cliver, Kamide 2005)

Other Amplitude IndicatorsOther Amplitude IndicatorsHathaway’s Law: Big cycles start early and leave behind a short Hathaway’s Law: Big cycles start early and leave behind a short period cycle with a high minimum.period cycle with a high minimum.

Amplitude-Period Effect: Large amp-Amplitude-Period Effect: Large amp-litude cycles are preceded by short litude cycles are preceded by short period cycles (currently at 130 period cycles (currently at 130 months months → average amplitude)→ average amplitude)

Amplitude-Minimum Effect: Large Amplitude-Minimum Effect: Large amplitude cycles are preceded by amplitude cycles are preceded by high minimum values (currently at high minimum values (currently at 12.6 12.6 → average amplitude)→ average amplitude)

Minimum Timing – Spotless DaysMinimum Timing – Spotless DaysDays without sunspots are an indicator of approaching sunspot cycle Days without sunspots are an indicator of approaching sunspot cycle minimum. The first day without spots typically occurs about 40 months minimum. The first day without spots typically occurs about 40 months before minimum (currently 43 months ago). The first month with 10 or more before minimum (currently 43 months ago). The first month with 10 or more spotless days typically occurs about 18 months before minimum (currently spotless days typically occurs about 18 months before minimum (currently 18 months ago). The first month with 20 or more spotless days typically 18 months ago). The first month with 20 or more spotless days typically occurs about 6 months before minimum (currently 4 months ago). occurs about 6 months before minimum (currently 4 months ago).

Minimum Timing – New Cycle SpotsMinimum Timing – New Cycle SpotsMinimum occurs when the number (increasing) of new cycle spots become Minimum occurs when the number (increasing) of new cycle spots become greater than the number (decreasing) of old cycle spots. We can differentiate greater than the number (decreasing) of old cycle spots. We can differentiate between new and old cycle spots by their latitude positions (old at low latitudes, between new and old cycle spots by their latitude positions (old at low latitudes, new at high latitudes) and magnetic polarities (opposite). The first new cycle spot new at high latitudes) and magnetic polarities (opposite). The first new cycle spot typically appears about 20 months before minimum (current candidate was 9 typically appears about 20 months before minimum (current candidate was 9 months ago). The second new cycle spot typically appears 10 months before.months ago). The second new cycle spot typically appears 10 months before.

Cycle 24 PredictionsCycle 24 Predictions

Based on the appearance of the remains of a new cycle spot at 33Based on the appearance of the remains of a new cycle spot at 33°N °N in late November 2006 and the number of spotless days, we expect to in late November 2006 and the number of spotless days, we expect to go through minimum in the spring of 2008. A large cycle (sunspot go through minimum in the spring of 2008. A large cycle (sunspot number ~ 160) would then peak in late 2011 while a small cycle number ~ 160) would then peak in late 2011 while a small cycle (sunspot number ~ 75) would peak in late 2012.(sunspot number ~ 75) would peak in late 2012.

ConclusionsConclusions

• The solar cycle displays numerous significant characteristics The solar cycle displays numerous significant characteristics which should be reproduced by dynamo models.which should be reproduced by dynamo models.

• Explicit Dynamo modeling predicts a larger than average and Explicit Dynamo modeling predicts a larger than average and late starting cycle 24 (sunspot number ~ 160).late starting cycle 24 (sunspot number ~ 160).

• Geomagnetic precursor activity also indicates a much larger Geomagnetic precursor activity also indicates a much larger than average cycle 24 (sunspot number ~ 160).than average cycle 24 (sunspot number ~ 160).

• Polar field strength indicates a smaller than average cycle 24 Polar field strength indicates a smaller than average cycle 24 (sunspot number ~ 75).(sunspot number ~ 75).

• The late start for cycle 24 is typical of smaller cycles.The late start for cycle 24 is typical of smaller cycles.

See: See: http://solarscience.msfc.nasa.gov/http://solarscience.msfc.nasa.gov/