“Think Big” is Plan at Solar Physics Workshop

Scientists from around the world will gather in Sunspot, New Mexico,
during Oct. 18-22, 2004, to try to get their minds around large-scale
structures on the Sun at the 22nd annual international science workshop of
the National Solar Observatory.

“By large, we mean anything from the size of a sunspot – about the size of
Jupiter – upward,” said K.S. “Sankar” Sankarasubramanian, chairman of the
conference. “And the seven major topics will start from the inside of the
Sun and work outward.”

“I thought this topic would be a good idea because it has never been
discussed before,” said Alexei A. Pevtsov, co-chair of the conference.
“These large-scale structures are an important part of solar activity in
general.”

Sankar is a research associate, and Pevtsov an associate astronomer, at
the National Science Foundation’s National Solar Observatory (NSO). The
conference is co-sponsored by the NSO, the National Science Foundation,
the National Aeronautics and Space Administration, and the U.S. Air Force
Office of Scientific Research. The Association of Universities for
Research in Astronomy (AURA) operates the NSO under a cooperative
agreement with the NSF.

More than 50 attendees are expected from across the world, including
representatives from India, Russia, Serbia and Montenegro, Uzbekistan, the
Czech Republic, and France.

The Jovian-scale theme of this year’s workshop might seem a bit at odds
with the thrust of the NSO’s efforts to develop a 4-meter Advanced
Technology Solar Telescope that will see structures on the scale of cities
on the surface of the Sun. The two actually are complementary, Sankar
explained since ultimately small-scale structures make up the larger ones,
and because the two extremes influence each other.

“If you look at a filament in high resolution,” he said, referring to
immense ribbons of cool gas that stand above the solar surface, “you see
that it has a lot of small-scale structures present. How do these small
flows in filaments affect whole filaments?”

Sankar and Pevtsov said that a comprehensive understanding of the physics
of the large-scale solar activity is necessary to understanding the
11-year sunspot cycle, variations in solar irradiance, and solar control
of space weather.

The conference sessions will start with activities inside the convection
zone, the upper layer of the Sun where hot gas circulates as if in an
immense, boiling pot (beneath this, the solar core and its overlying
radiative zone rotate as a solid body). The convection zone has massive
jet streams akin to those that control terrestrial weather, as well as
giant gas cells that contain up-down circulation patterns. At the
photosphere or visible surface (where density of the convection zone drops
enough for gas to become transparent) and the hot chromosphere above it,
activity appears as complexes of large-scale magnetic fields, and patterns
of filament channels.

This organization continues into the halo-like corona as holes in the
corona that form the solar wind, and as eruptions that form coronal mass
ejections, both helping drive space weather. An unbreakable thread running
through all the topics is magnetism that is generated by a dynamo inside
the convection zone and which manifests itself in sunspots and flares
whose numbers come and go every11 years.

Despite the size and intensity of the fields, little is known about how
the various parts connect and interact.

“High in the corona you have large areas where you see bright structures
with loops that connect magnetic fields,” Pevtsov explained. “These seem
to be self-contained. It seems that there should be a continuity from the
dynamo inside the Sun through the solar atmosphere and into the corona.”

Issues this workshop intends to address include:

• What is the role of large-scale structures in solar activity?
• What is the physical relationship between patterns observed in different layers of solar atmosphere?
• How are photospheric and coronal structures related to the underlying dynamo or circulation in the convective zone?

Proceedings from the conference will be published in 2005 in cooperation
with the Astronomical Society of the Pacific.

Details of the workshop are on line at:
http://www.nso.edu/general/workshops/2004/ws22.html

CONTACT DATA

Media wishing to cover the workshop should contact:

Dave Dooling, Education and Public Outreach Officer

National Solar Observatory

dooling@nso.edu

or

Jackie Diehl, Education and Public Outreach

National Solar Observatory

jdiehl@nso.edu 505-434-7003