Determining the Magnetic Environment in Which Solar Activity Occurs
Final rept. 1 Jul 1994-30 Jun 1998
STANFORD UNIV CA CENTER FOR SPACE SCIENCE AND ASTROPHYSICS
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This grant has supported a number of different activities related to the primary Air Force grant F49620-95- 1-0008, Environmental Conditions Responsible for Solar Activity. Under this AASERT grant, students Frankie Liu and Aaron Birch approached several problems relevant to solar activity. Liu calculated the coronal magnetic field from vector magnetograph data when the field is assumed to be force-free but not current-free. Liu solved the problem by the method of simulated annealing. This approach led to the development of a program that quickly converged to a stable configuration, leading to a resolution the 180-degree ambiguity in the transverse component of the magnetic field. Liu also worked on the general problem of coronal heating by analyzing images from the Yohkoh SXT X-ray telescope. Lius analysis confirmed the conclusion drawn from earlier studies that the heating occurs at a considerable height above the solar surface, certainly above 0.5 solar radius for the region investigated. Liu concluded that, in open field regions, the mechanism of coronal heating is closely related to the mechanism that drives the solar wind. Finally, Liu investigated whether fast magnetoacoustic waves, generated from the chromosphere or below, can couple into slow magnetoacoustic modes which can dissipate their energy in the corona. Liu found that the coupling is small, so that this process is not promising as an explanation of coronal heating.
- Electricity and Magnetism