Electron-cyclotron maser emission from the sun and stars: Variations with plasma temperature and density

Abstract

Very bright and highly circularly polarized radio bursts from the Sun, the planets, flare stars, and close binary stars are attributed to the electron-cyclotron maser instability. The mode and frequency of the dominant radiation from the maser instability is shown to be dependent on the plasma temperature and the ratio ω _p /Ω _e of the plasma frequency to the electron-cyclotron frequency. For the emission from the Sun ω _p /Ω _e is probably greater than 0.3 and for 0.3 < ω _p /Ω _e < √2 the emission can be either in the x-mode at the second harmonic or in the o- and/or z-modes at the fundamental. For higher ω _p /Ω _e , the emission moves to higher harmonics of Ω _e with the emission being predominately in the z-mode when ω _p /Ω _e > √3.