The influence of negatively charged heavy ions on the kinetic Alfven wave in a cometary environment

Abstract

Kinetic Alfven waves are important in a wide variety of areas like astrophysical, space and laboratory plasmas. In cometary environments, waves in the hydromagnetic range of frequencies are excited predominantly by heavy ions. We, therefore, study the stability of the kinetic Alfven wave in a plasma of hydrogen ions, positively and negatively charged oxygen ions and electrons. Each species was modeled by drifting ring distributions in the direction parallel to the magnetic field; in the perpendicular direction the distribution was simulated with a loss cone type distribution obtained through the subtraction of two Maxwellian distributions with different temperatures. We find that for frequencies ω * < ω cH + (ω * and ω cH + being respectively the Doppler shifted and hydrogen ion gyro-frequencies), the growth rate increases with increasing negatively charged oxygen ion densities while decreasing with increasing propagation angles, negative ion temperatures and negative ion mass.

Properties of dispersive Alfvén waves: 3. Hydrodynamics (Very Low, Intermediate, and Low Density Plasmas)

“…For DAWs, the perturbations of the electron and proton densities are almost equal in the majority of cases; therefore, in the hydrodynamic approach (as in the kinetic one), we calculate the wave charge den sity ρ from the third Maxwell equation [1]: (7) Taking into account that the main electric field component for DAWs is E x (that is, E z Ӷ E x ) and, besides, the dispersive properties of Alfvén waves appear generally at k x ӷ k z , we can rewrite (7) in the form (8) Expressions (7) and (8) will be input into the calculation of the wave charge density.…”

“…The unique ness of these properties enables one to consider Alfvén waves as one of the most promising sources of the energy transfer and particle heating in space [6,9,17,20] and as a very effective mechanism of charged particle acceleration [5,11,12,14]. It should be noted that Alfvén waves can play an important role in the formation of solar faculae [19] and spicules [18], in the magnetic field reconnection [16], in the formation of flares [4], in cometary tails [7], in the generation of convection cells [13], cavities [3], bubbles [15], etc.…”