space climate and the recent unusual solar minimum sarah gibson drawing upon results of iau...

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

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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

11

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.

1417

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

15

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

19

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

20

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)?

21

Judge and Thompson 2012

Giampapa, 2012; Schmitt, 2012; Olah et al., 2012; Saar and Testa, 2012; Valio, 2012

25

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)

29

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

30

• 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

31

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