Ballooning instability of flare coronal loops

Yu.T. Tsap$^1$, Yu.G. Kopylova$^2$, A.V. Stepanov$^2$, V.F. Melnikov$^3$, K. Shibasaki$^4$

$^1$Crimean Astrophysical Observatory, Ukraine
$^2$Pulkovo Astronomical Observatory, Russian Academy of Sciences, St.-Petersburg 196140, Russia
$^3$Radiophysical Research Institute (NIRFI), Nizhny Novgorod, 603950, Russia
$^4$Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Minamisaku, Nagano 384-1305, Japan

Within the framework of the ideal MHD the excitation of the ballooning instability in the toroidal coronal loops is analyzed using the energy method. Kink oscillations are able excite the ballooning instability when the plasma beta $\ll$ 1. Modulation of gyrosynchrotron emission caused by kink oscillations is considered. It has been shown that intensity of gyrosynchrotron emission for optically thin sources is the most sensitive with respect to Alfven disturbances. The effects of the instability in the light of some observations are discussed.