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Published September 1971 | Published
Journal Article Open

Magnetic fields, bremsstrahlung and synchrotron emission in the flare of 24 October 1969

Abstract

An impulsive flare October 24, 1969 produced two bursts with virtually identical time profiles of 8800 MHz emission and X-rays above 48 keV. The two spikes of hard X-rays correspond in time to the times of sharp brightening and expansion in the Hα flare. The first burst was not observed at frequencies below 3000 MHz. This cut off is ascribed to plasma cutoff above the low-lying flare. A model of the flare based on Hα observations at Big Bear shows that the density of electrons with energy above 10 keV is 5 × 10⁷ if the field density is 1011. The observed radio flux would be produced by this electron distribution with the observed field of 200 G. The Hα emission accompanying the hard electron acceleration is presumed due to excitation of the field atoms by the hard electrons.

Additional Information

© 1971 Kluwer Academic Publishers. Provided by the NASA Astrophysics Data System. Received 10 February 1971; Issue Date September 1971. We wish to thank Dr Kane for the use of his X-ray data and several valuable discussions; Drs Castelli, van Allen, and Bhatnagar for their data, and Dr Allan Moffet for several discussions on the question of gyro-synchrotron emission. The Caltech group was supported by NASA under grant NGR 05002034 and NSF under grant GA 24015; the Berkeley group by NASA, under contract NAS 5-9094 and grant NSL 05003017.

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Created:
September 15, 2023
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October 23, 2023