Microwave Response to the Symmetric Fast Magnetosonic Wave

The frequency spectra of the intensity I_f of microwave radiation, which were obtained by integration along the line of sight and expressed in solar flux units, as functions of the radiation frequency f for four GS sources with different transverse sizes r/w and for the model parameters corresponding to Fig. 4a: A = 0.10, d = 3, and θ = 87°. The radiation intensity spectra of the unperturbed slab are shown by solid lines. The dashed lines correspond to the emission spectra of the perturbed layer at the intensity fluctuation maximum and the dotted lines, at the minimum.

Kupriyanova E. G.; Kaltman T. I.; Nakaryakov V. M.; Kolotkov D. Yu.; Kuznetsov A. A.

We study the observed response of microwave radiation to the perturbation of a transversely inhomogeneous plasma slab, which is stretched along a uniform magnetic field, by a symmetric (sausage-mode) fast magnetosonic wave guided by the slab. Two-dimensional modeling was carried out within the framework of the analytical solution of a system of linearized magnetohydrodynamic equations. The accelerated electrons filling only part of the slab were considered as the source of gyrosynchrotron radiation. It is shown that for gyrosynchrotron sources with a transverse size significantly smaller than the slab width and for all angles of sight there is enhancement of the microwave response to a fast magnetosonic wave. Namely, the modulation depth of the radiation is an order of magnitude higher than the initial wave amplitude, while an opposite effect was detected for gyrosynchrotron sources larger than the slab width. Contrast of the modulation depth of the radiation from narrow and wide sources increases with increasing difference of the densities outside and inside the slab. It was found that the microwave response of the slab to a fast magnetosonic wave is nonlinear, which may lead to a complete disappearance of the periodic response or its frequency doubling for certain combinations of the model parameters.