Gyrosynchrotron instability in a plasma with a beam of moderately relativistic electrons

The possibility of gyrosynchrotron instability development in a plasma with moderately relativistic electrons is revealed. The absorption and emission coefficients are numerically calculated for a Gaussian distribution function of these electrons. It shows the presence of emission bands where the absorption coefficientµ is negative, and their dependence on the halfwidth,v, of the Gaussian as well as on the observation angle is established. In conclusion, results obtained are applied for the interpretation of microwave bursts registered during solar flares.