Physics of the Weird Solar Minimum:

New observations of the Sun

Dr. E.J. ZitaThe Evergreen St. College

Olympia WA 98505zita@evergreen.edu

AbstractWhile solar physicists expected more sunspots, flares, and coronal mass ejections by now, the Sun has defied most predictions by persisting in a relatively quiet state for an unusually long time. Can we tell whether this solar minimum is likely to ease in the next decade, or if it may become a Maunder-type minimum? What evidence is there for mechanisms that might explain the observed delayed and low-amplitude magnetic activity? What effects could decreased solar activity have on Earth's climate?

Evergreen undergraduates study the Sun with colleagues who built the new Solar Dynamics Observatory (SDO). Students analyzed flows vs. magnetic field tilts; analyzed waves of UV light in active regions; developed a software suite to enable the public to engage with solar dynamics; and cataloged movies of solar events for public release. We use data from the high-resolution HINODE satellite and from the new full-disk SDO. Zita studied the solar dynamo, and found that resistivity gradients can drive magnetic advection. We summarize our work and the light it may shed on questions such as those above.

Extended Solar Minimum is weird

Observations vs Understanding

We can learn THAT the Sun is behaving weirdly with simple ground-based observations – e.g. sunspots.

To learn WHY the Sun is behaving weirdly requires more sophisticated science:

• Theories and simulations• predictions and tests• space-based observations

Solar min. is due to Magnetic DynamoShearing of poloidal fields by differential rotation to produce new toroidal fields, followed by

eruption of sunspots.

Spot-decay and spreading to produce new surface global

poloidal fields.

Transport of poloidal fields by meridional circulation (conveyor belt)

toward the pole and down to the bottom, followed by regeneration of new toroidal fields of opposite sign.

Courtesy of Dr. Mausumi Dikpati

Contours: toroidal fields at CZ base Gray-shades: surface radial fields

Observed NSO map of longitude-averaged photospheric fields

Solar dynamo evolution of magnetic fields

Dikpati, de Toma, Gilman, Arge & White, 2004, ApJ, 601, 1136

Magnetic Dynamo is sensitive to Diffusivity

Diffusivity Gradients drive Advection of Magnetic Fields

• graphics

Theories to explain Weird Solar Minimum

• Hathaway

• Ulrich

• Saba & Strong

New data to test theories:

Solar Dynamics Observatory (SDO):

AIA = Atmospheric Imaging Assembly (12 , 1 arcsec, 10 sec)

HMI = Helioseismic & Magnetic Imager (continuum, doppler, LOS&vector magnetograms)

EVE = Extreme EUV Expt

What are wave dynamics in active regions?

D1.00006: Waves and oscillations in the solar atmosphereChristopher Ballou , Mark Cheung , E.J. Zita , Christina Smith

How do flows change where B fields tilt?

D1.00005: Solar Plasma Flows and Convection in Oblique Magnetic Fields

: Christina Smith, E.J. Zita, Neal Hurlburt

How can the public access SDO data?

Talk at 3:56 in Science 142: H2.00006 : Solar Tutorial and Annotation Resource (STAR): Clay Showalter

Poster D1.00004: Sharing new data from Solar Dynamics Observatory: Benji Friedman

Impacts of solar min. on Earth?

• Lower solar wind pressure & strangely lower mean solar B – less buffer against cosmic rays

• Lower solar irradiance (only ≈ 0.1% - won’t save us from anthropogenic global warming)

• Historical correlations – causal or not? – Maunder Minimum / Little Ice Age– Medieval Maximum / warm period

• Current extended solar minimum appears to be easing – more sunspots showing up

• How high will next max go? Normal range?

AcknowledgementsWe gratefully acknowledge the use of Mausumi Dikpati's kinematic dynamo model, and guidance from Dr. Dikpati and Dr. Peter Gilman (HAO/NCAR, Boulder, CO 80301).We thank Dr. Neal Hurlburt and colleagues at Lockheed Martin Solar and Astrophysics Laboratory for providing guidance and facilities for recent research (Palo Alto, CA 94304), and Dr. Phil Scherrer for sponsoring Evergreen students at Stanford’s Summer Research College.

This work was partially supported by NASA grants NNH05AB521, NNH06AD51I and the NCAR Director's opportunity fund; NSF grant 0807651, the Visitor Program of the High Altitude Observatory (HAO) at NCAR, and The Evergreen State College's Sponsored Research program.

The National Center for Atmospheric Research (NCAR) is sponsored by the National Science Foundation (NSF). LMSAL is partly supported by NASA.

Physics of the Weird Solar Minimum:

New observations of the Sun

Dr. E.J. ZitaThe Evergreen St. College

Olympia WA 98505zita@evergreen.edu