space climate and the recent unusual solar minimum sarah gibson drawing upon results of iau...
TRANSCRIPT
Space Climate and the Recent Unusual Solar Minimum
Sarah Gibson
drawing upon results of IAU
Symposium 286 Proceedings
(and other recent publications)
Outline
•Introduction: Solar Cycle From Sun to Earth
•Grand Minima: Causes and Consequences
•The Recent Solar Minimum: Was it Peculiar?
•The Sun: Is it Peculiar (among Stars)?
Outline
•Introduction: Solar Cycle From Sun to Earth
The Solar Butterfly Diagram
The 11-year Sunspot cycle
Solar Cycle: At the Sun
Solar Cycle: At the Sun
Solar Cycle: In the Solar Wind
QuickTime™ and aVideo decompressor
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MIN MAX
courtesy P. Riley
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Solar Cycle: At the Earth
Thermospheric density
Solomon et al. 2010
Outline
•The Recent Solar Minimum: Was it Peculiar?
• Sunspots
Priest, 2012
Long, slow-to-arrive minimum, with very few sunspots
9
Svalgaard, 2012
SSN revised
Group Sunspot Number vs. Wolf (Zurich) Sunspot Number:
• WSN needs weighting based on sunspot size (20% increase < 1940s)
10
No Modern Maximum!
Group Sunspot Number vs. Wolf (Zurich) Sunspot Number:
• GSN needs increase by 50% < 1885
SSN revised
Svalgaard, 2012
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The recent solar minimum
Was it peculiar?
Courtesy L. Svalgaard
Maybe not: Long and quiet minima have occurred (on century
time scale e.g. Gleisberg cycle)
Outline
• The Recent Solar Minimum: Was it Peculiar?
• weak polar magnetic field
• Magnetic morphology
de Toma, 2012
13
The Porcupine Sun!
Not as dipolar as prior space age minima...Gibson and Zhao, 2012
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Courtesy Predictive Science Inc.
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Solar wind velocity from STEL interplanetary scintillation data
Fast wind threads the ecliptic, long and strong high-speed solar wind streams in 2008
Tokumaru et al., 2011
1996
2008
de Toma, 2012
Maris et al., 2012
1996200720082009
Vmax22/23
Vmax23/24
Vlength22/23
Vlength23/24
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The recent solar minimum
Was it peculiar?
Weak dipole (porcupine): again, probably not on century time-
scales
de Toma, 2012
see also: Luhmann et al., 2012; Tlatov et al., 2012
Outline
•The Recent Solar Minimum: Was it Peculiar?
• weak polar field --> porcupine sun
• Morphology
• Longitudinal variation--> periodicities
Periodicities (9, 13, 27 day) of wind in aurora and radiation belt
The Earth was ringing for most of 2008
Gibson et al., 2009
2008
1996
Vsw auroral power rad. belt
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Courtesy Neal Sheeley
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see also: Echer et al., 2012; de Toma, 2012
21
Love et al., 2012
Strong periodicity: Combination of
• warped heliospheric magnetic structure• long-lived, low-latitude coronal holes• low activity
2008-2009
2006
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The recent solar minimum
Was it peculiar?Periodic behavior? maybe not
entirely...
courtesy G. de Toma But then again, the recent minimum had unusually strong and sustained periodic behavior compared to prior minima in the geomagnetic record - extended declining phase (see also Luhmann, 2012)
Love et al., 2012
Outline•The Sun: Is it Peculiar (among Stars)?
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Judge and Thompson 2012
Giampapa, 2012; Schmitt, 2012; Olah et al., 2012; Saar and Testa, 2012; Valio, 2012
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The Sun: Is it peculiar? Not in terms of cycling
Judge and Thompson, 2012
The Sun: Is it peculiar?Maybe? or do we just
need to fill in the middle?
Judge and Thompson, 2012
Need to better understand mechanism(s) underlying solar dynamo
Brandenburg & Guerrero, 2012; Candalaresi & Brandenburg, 2012; del Sordo et al., 2012; Elsworth et al., 2012; Guerrero et al., 2012; Warnecke et al., 2012
The Maunder Minimum
• What do we know observationally about the Maunder minimum?
• sudden onset, gradual recovery (Usoskin et al., 2000)
• Ice core/tree ring cosmic-ray data indicate magnetic cycles continue even without sunspots (Beer et al., 1998; Miyahara et al., 2004)
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The Sun: Is it peculiar?The jury’s out in terms of
Maunder-type minima
Judge and Thompson, 2012
Warning: models indicate cycling stars could masquerade as non-cyclic or Maunder-type minima stars, if surface flux distribution (polar-to-equator) oscillates out-of phase Isik, 2012
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• What do we know from models? Nandy, 2012• Stochastic fluctuations, e.g., in the meridional flow and the dynamo α-effect (Charbonneau & Dikpati 2000)
• Non-linear feedback of the fields on the flows (Tobias 1997) that may lead to chaotic modulation
• Sudden changes in dynamo ingredient: induce Maunder-type minimum by decreasing poloidal field (alternatively, by decreasing meriodonal flow--i.e. Karak (2010))
• Cyclic behavior continued in the radial (solar wind) magnetic field)• Sunspot flux emergence recovers by (non-Babcock-Leighton) alpha-effect
Outline•Grand Minima: Causes and Consequences
Choudhuri, 2012; Karak & Choudhuri, 2012
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Rozanov et al., 2012
Dalton-like minimum conditions• Solar irradiance• Spectral solar irradiance• Energetic electron preciptation• Solar protons and galactic cosmic rays
Solar activity decrease can modulate anthropogenic effects:• Ozone recovery delay• Greenhouse warming compensated partially• Stratospheric cooling (anthropogenic) enhanced by solar forcing•varies by atmospheric layer and geographical region
Solar irradiance variability most significant.
Effect of solar Grand Minimum on climate
see also Kollath et al., 2012; Souza-Echer et al. 2012; Usoskin et al., 2012
How far back can we go? How Grand can Minima get?
Vaquero, 2012
Usoskin et al., 2012
Cliver, 2012
-8000
-7000
1000
Conclusions
Was the recent solar minimum unusual?
•For the space age, yes (long, low SSN, non-dipolar Sun)•For the sunspot record, no (last century, e.g.)•For the eclipse record, maybe not (non-dipolar porcupine structure seen)•For the geomagnetic record, perhaps (periodic behavior very strong)
Is the Sun unusual?
•Not in terms of cycling•Dynamo nature?•Maunder-type minima?
Long-term solar/stellar variability implications
•Climate•Space climate•Other planets Bertucci, 2012•Biology - on Earth OsarioRosales & Mendoza, 2012
• and other planets! Abreveya, 2012