Download Physics of the Weird Solar Minimum: New observations of the Sun

Physics of the Weird Solar Minimum:
New observations of the Sun
Dr. E.J. Zita
The Evergreen St. College
Olympia WA 98505
[email protected]
Abstract
While 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
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 Dynamo
Shearing 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
Solar dynamo evolution of magnetic fields
Contours: toroidal fields at CZ base
Gray-shades: surface radial fields
Observed NSO map of longitude-averaged photospheric 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 l, 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 atmosphere
Christopher 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?
Acknowledgements
We 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. Zita
The Evergreen St. College
Olympia WA 98505
[email protected]