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A Gyro-Synchrotron Maser in the Solar Corona?

Published online by Cambridge University Press:  25 April 2016

D. B. Melrose  and
S. M. White
D. B. Melrose
Affiliation:
Department of Theoretical Physics, Australian National University
S. M. White
Affiliation:
Department of Theoretical Physics, Australian National University
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Extract

Stewart (1978) has reported four moving type IV bursts observed with the Culgoora radio heliograph at 43, 80 and 160 MHz. After an early phase, the brightness temperatures of the observed bursts decreased with increasing frequency and with time. The highest brightness temperature observed at 43 MHz was 1010K, and it seems that the brightness temperature would have been still higher at even lower frequencies. Existing theoretical ideas on moving type IV bursts are based on data (at 80 MHz primarily) which included no brightness temperatures in excess of 109K. the accepted interpretation involved gyro-synchrotron radiation from mildly relativistic electrons (energies ≈ 100 keV); reabsorption by the electrons themselves restricts the brightness temperature to less than about 100 keV ≈ 109K (Wild and Smerd 1972, Dulk 1973). Stewart’s (1978) new data at 43 MHz require that this accepted interpretation be modified; he has suggested that higher energy electrons are involved. An alternative suggestion is explored here, namely that the absorption might be negative. In other words, the high brightness temperatures observed could be due to a gyro-synchrotron maser involving electrons with energies of about 100 keV.

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Contributions
Information
Publications of the Astronomical Society of Australia , Volume 3 , Issue 3 , 1978 , pp. 231 - 233
Copyright
Copyright © Astronomical Society of Australia 1978

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