Kinetic Alfven Waves Excited by Cometary Newborn Ions with Large Perpendicular Energies

Stability of the kinetic Alfven wave in a plasma of hydrogen, oxygen and electrons is studied. Each species is modeled by drifting ring distributions in the direction parallel to the magnetic field, while in the perpendicular direction the distribution is simulated with a loss cone type distribution obtained through the subtraction of two Maxwellian distributions with different temperatures. It is found that for frequency w^* < Ｗ_H with w^* and Ｗ_H the Doppler shifted and hydrogen ion gyro-frequencies, respectively, the growth rate of the kinetic Alfven wave increases with the increase in propagation angles and density of oxygen ions. On the other hand, for frequencies w^* < Ｗ_O with Ｗ_O the oxygen ion gyro-frequency the growth rate is independent of the oxygen ion density.