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Session 5 - SOHO Corona III.
Oral session, Friday, June 27
Ballroom A, Chair: John Mariska

[5.06] Coronal Heating and the Photospheric Magnetic Field

C. E. Parnell, P. A. Sturrock (Stanford University)

Since magnetic field typically plays a role (either active or passive) in coronal heating theories, it may be possible to evaluate these theories by investigating the relationship between the coronal energy budget (the total power requirement of the corona) and measurable properties of the photospheric magnetic field. The X-ray flux is a useful proxy for the total power required to maintain the corona, so we have examined the relationship between the total X-ray flux, as measured by the GOES instruments, and the total magnetic flux, as estimated from the NSO instrumentation at Kitt Peak.

We use this relationship to test the recent proposal that coronal heating is due to sudden magnetic relaxation. According to this concept, reconnection in the chromosphere of the footpoint regions of two oppositely directed flux tubes leads to a new flux tube, with widely separated footpoints, which erupts rapidly and generates sound waves that heat the corona. We adopt a simple "kinetic theory" model for the photospheric and chromospheric processes, and so obtain an estimate of the magnetic flux reconnection rate in terms of the mean field strength and of the parameters (diameter, flux and random speed) that characterize the elementary flux elements. The sudden magnetic relaxation model gives a simple relation between the magnetic flux budget and the coronal energy budget. In this way, we obtain a theoretical relationship between the coronal energy budget and the mean photospheric magnetic field strength that we compare with the available observational data.

This work was supported by NASA grants NAS 8-37334 and NAGW-2265, and by Air Force grant F49620-95-1-0008.

Program listing for Friday