VLA Observations of a High Coronal Flare

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Session 7 -- Solar Activity
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[7.06] VLA Observations of a High Coronal Flare

J.P. Raulin, N. Gopalswamy, M.R. Kundu (University of Maryland), N. Nitta (Lockheed Palo Alto Research Lab)

We present radio observations of a coronal flare which occurrred on 1993 April 22, in a weak magnetic field region to the west of AR 7477. The observations were made by the Very Large Array (VLA) at 20 and 90 cm. The event consists of bright (brightness temperature of $10^{10} K$) unpolarized bursts, followed by a longlasting unpolarized continuum with moder ately high brightness temperature (2-3 $10^{9} K$) in the high corona (90 cm observations). The low coronal counterpart of this flare is a weak and moderatly polarized 20 cm radio emission. Full disk Yohkoh images show that the corresponding radio emission is located in or above magnetic loops connecting AR 7477 and its neighborhood. The presence of permanent and non-varying noise storm associated with AR 7477 seems to indicate that the overall magnetic field structure of the active region is unaffected by the flare. The coronal radio source which is indicative of acceleration of electrons to nonthermal energies, is not associated with major $H\alpha$ emissio n nor with bright X ray emission. The absence of any detectable circular polarization, as well as the high brightness temperature, seems to indicate that the 90 cm emission is second harmonic plasma emission.

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