Effect of ion beam on electromagnetic ion cyclotron instability in hot anisotropic plasma-particle aspect analysis

摘要

Using the general loss-cone distribution function electromagnetic ioncyclotron (EMIC) instability affected by up going ion beam has been studiedby investigating the trajectories of charged particles. The plasmaconsisting of resonant and non-resonant particles has been considered. It isassumed that the resonant particles participate in energy exchange with thewave, whereas non-resonant particles support the oscillatory motion of thewave. The effect of ion beam velocity on the dispersion relation, growthrate, parallel and perpendicular resonant energy of the EMIC wave withgeneral loss-cone distribution function in hot anisotropic plasma isdescribed by particle aspect approach. The effect of beam anisotropy andbeam density on electromagnetic ion cyclotron instabilities is investigated.Growth length is derived for EMIC waves in hot anisotropic plasma. It isfound that the effect of the ion beam is to reduce the energy oftransversely heated ions, whereas the thermal anisotropy of the backgroundplasma acts as a source of free energy for the EMIC wave and enhances thegrowth rate. It is observed that ion beam velocity opposite to the wavepropagation and its density reduces the growth rate and enhance thereduction in perpendicularly heated ions energy. The effect of ion beamanisotropy on EMIC wave is also discussed. These results are determined forauroral acceleration region. It is also found that the EMIC wave emissionsoccur by extracting energy of perpendicularly heated ions in the presence ofan up flowing ion beam.