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Astron. Astrophys. 358, 776-788 (2000)


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Saturation of electron cyclotron maser by lower-hybrid waves

G. Fleishman 1 and K. Arzner 2

1 Ioffe Institute for Physics and Technology, 194021 St. Petersburg, Russia (gregory@sun.ioffe.rssi.ru)
2 Institut für Extraterristrische Physik, P.O. Box 1603, 85740 Garching, Germany (kja@mpe.mpg.de)

Received 22 July 1999 / Accepted 2 March 2000

Abstract

We perform a numerical study on the quasilinear relaxation of an electron cyclotron maser on the initially dominant mode. We focus thereby on a situation where the initially dominant modes are quasi-electrostatic lower hybrid (lh) waves, which have not been treated in preceding studies. To this end, we chose [FORMULA] ([FORMULA]: plasma-, [FORMULA]: electron cyclotron frequency) and an initial losscone distribution of energetic electrons of the form [FORMULA] (p: momentum, µ: pitch angle cosine). Superimposed on this is a damping Maxwellian background. From our calculations, we find that multiple peaks in the lower-hybrid wave intensity can occur if the initial loss cone distribution is sufficiently broad. We also find that quasilinear relaxation with respect to lower-hybrid waves does not destroy the capability of the electron distribution to amplify transverse (XOZ) waves, which therefore become dominant at a later stage. The comparison with observations shows that the calculated shape of a single peak in the lower-hybrid energy density displays a remarkable similarity to solar radio spikes.

Key words: Sun: radio radiation – masers

Send offprint requests to: K. Arzner

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000

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