Modulation of gyrosynchrotron emission in solar and stellar flares by slow magnetoacoustic oscillations

¹ Physics Department, University of Warwick, Coventry CV4 7AL, UK e-mail: valery@astro.warwick.ac.uk
² Radiophysical Research Institute (NIRFI), Nizhny Novgorod 603950, Russia e-mail: meln@nirfi.sci-nnov.ru

Received: 29 July 2005
Accepted: 20 September 2005

Abstract

Gyrosynchrotron emission generated by non-thermal electrons in solar and stellar coronal flares can be efficiently modulated by slow magnetoacoustic oscillations in the flaring loops. The modulation mechanism is based upon perturbation of the efficiency in the Razin suppression of optically thin gyrosynchrotron emission. Modulation of the emission is in anti-phase with the density perturbation in the slow wave. The observed emission modulation depth can be up to an order of magnitude higher than the slow wave amplitude. This effect is more pronounced at lower frequencies. Observations with spatial resolution, together with analysis of the modulation frequency, are shown to be sufficient for providing the information needed to identify the mode.