DURHAM, N.H. -- Even during its relatively quiet period,
the Sun has surprised scientists with a quirky dual
A University of New Hampshire scientist was one of two researchers spearheading a comprehensive study of the Sun during a month of its most recent quiet period, using instruments not previously available.
Antoinette Galvin, research associate professor in the UNH Institute for the Study of Earth, Oceans and Space, and John Kohl of the Harvard-Smithsonian Center for Astrophysics helped organize an international team of scientists compiling data that will be useful as the Sun reaches its period of maximum sunspot activity in the year 2000.
The Sun exhibits an approximately 11-year cycle of sunspots, with a shorter period from minimum to maximum than for maximum back to minimum. At solar minimum, there are few sunspots and related magnetic activity, such as flares and coronal mass ejections. During this time, the surface of the Sun is dominated by polar coronal holes -- a major source of high speed solar wind.
Galvin and Kohl state that the project's objective was to gain an understanding of the large-scale, stable structures that dominate the solar corona at solar minimum. The corona is the outermost layer of the solar atmosphere, and Galvin and Kohl say that understanding the large-scale corona is fundamental to understanding how and where the solar wind is accelerated. The solar wind, an outflow of particles and magnetic fields, can affect communications on Earth, especially during the solar maximum.
"One may think the studying the Sun at solar minimum would be boring," says Galvin. "Not so! Even we scientists were surprised by the complexity and dynamics we saw on the Sun during solar minimum."
In fact, during the month of observations, the Sun presented Galvin and the team with two opposing faces: one dominated by a flaring active region situated next to a coronal hole that extended from the north pole down past the equator. "This coronal hole, dubbed 'the elephant's trunk' for its shape, was the source of solar winds with speeds of more than 600 kilometers per second, as measured by near-Earth satellites," says Galvin.
"The second face was completely the opposite -- quiet and simple," she adds.
Whole Sun Month (WSM) was a two-year collaborative effort of the Inter-Agency Consultative Group (IACG) Campaign 4 and the Solar and Heliospheric Observatory (SOHO) Working Group Joint Observing Program 44. Under its auspices, an international and interdisciplinary group of scientists studied the Sun from Aug. 8 to Sept. 10, 1996, a period known as solar minimum.
"This was a major international effort involving American, European and Japanese spacecraft and solar ground observatories," says Galvin, an IACG Campaign leader.
Although some results have been reported at meetings of the American Geophysical Union and other organizations and in some journal articles, the first comprehensive, peer reviewed compilation appears in the current issue of the Journal of Geophysical Research.
Funding for the Whole Sun Month study was provided by NASA, the United Kingdom PPARC, National Science Foundation, European Space Agency, and other agencies.
By Carmelle Druchniak
UNH News Bureau