THE DICHOTOMY OF THE MECHANISMS OF DECAMETER RADIO EMISSION FROM JUPITER: THE INFLUENCE OF STREAMER INHOMOGENEITIES AND MHD PERTURBATIONS IN THE SOURCE

Abstract

There are analyzed a model of the source of DAM radiation bursts which are activated under the MHD waves excitation in the Jupiter lower magnetosphere in a presence of ionized streamer-like inhomogeneities of limited thickness (1-100 km). There was studied the formation of an anisotropic kinetic distribution of electrons, which leads to the generation of Jupiter DAM radiation bursts under the various scenarios. It was investigated the influence of gas-dust flows in the Io-Jupiter tube, the ionization processes and the diffusion effects in the streamer plasma to the creation the cone-type kinetic distribution of electrons. On the other hand, it has been shown that Alfven waves, due to the fluctuations of electric fields, are to form of both cone-like electron distribution (primarily on the streamer periphery) and beam-like distribution with the beams of accelerated electrons (primarily inside the streamer), which further run along the streamers at speeds of about 0.1c and have been modulated by a "longitudinal" MHD wave with a length of about 1000 km and a period of about 1 second. The streamer oscillations in the direction tangential to the magnetic field lines lead to the excitation the fast magneto-sonic waves (at about the ion cyclotron resonance frequencies). The beams of accelerated electrons of along the magnetic field lines generate the plasma waves in the same direction (at about the electron cyclotron resonance frequency). At the same time, plasma perturbations create a stratification of the steamer-tube structure into ultrafine threads of ionized plasma, and they contribute to the ultrafine modulation of bursts of DAM radiation with millisecond periods. Finally, it is shown in detail how all these processes lead to activate the Jupiter DAM radiation bursts in that source at the frequency of electron cyclotron resonance by different generation mechanisms, such as the Maser Cyclotron or Cherenkov mechanisms of generation, and with different burst’s properties.