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Session 33 - Dynamics of Solar Magnetic Fields.
Oral session, Tuesday, June 11
Wisconsin Center,

[33.04] Coronal Heating in Active Regions as a Function of Global Magnetic Variables

G. H. Fisher, D. W. Longcope (UC, Berkeley), T. R. Metcalf, A. A. Pevtsov (U. Hawaii)

A comparison of X-ray images of the Sun and full disk magnetograms shows a correlation between the locations of the brightest X-ray emission and the locations of bipolar magnetic regions. This correspondence has led to the generally accepted idea that magnetic fields play an essential role in heating the Solar corona. To quantify the relationship between magnetic fields and coronal heating, we have compared the X-ray luminosity of many different Active Regions with several global (integrated over entire active region) magnetic quantities. The X-ray measurements were made with the SXT Telescope on the Yohkoh spacecraft; magnetic measurements were made with the Haleakala Stokes Polarimeter at the University of Hawaii's Mees Solar Observatory. Our combined dataset consists of 333 vector magnetograms of active regions taken between 1991 and 1995; SXT luminosities consist of time averages of SFD images of the given active region taken within \pm 4 hours of each magnetogram. Global magnetic quantities include the total unsigned magnetic flux, area integrals of B^2, J_z^2 (J_z is the vertical component of the electric current density), and the best-fit \alpha of the linear force-free field for the entire active region (\nabla \times B = \alphaB). Our results show clear and unmistakeable relationships between the X-ray luminosity and most of these magnetic variables. The relationship between total unsigned magnetic flux and X-ray luminosity is especially compelling, holding over 2 orders magnitude in both quantities. These measurements provide important contraints on coronal heating mechanisms. This work was supported in part by NASA grant NAGW-3429, NSF grant AST-9218085, and Cal Space grant CS-17-95.

Program listing for Tuesday