A New N+ Band of Electromagnetic Ion Cyclotron Waves in Multi-Ion Cold Plasmas

Abstract

The dispersion relation for electromagnetic ion cyclotron (EMIC) waves is analyzed for a multi-ion cold plasma. Several cases accounting for the relative contribution of the nitrogen (N+) and the oxygen (O+) ions and wave normal angle (θ) are presented. It is found that the presence of N+ significantly changes the dispersion properties of EMIC waves, leading to a new frequency band with additional cutoff, crossover, and resonance frequencies just above the oxygen cyclotron frequency ((Formula presented.)). The method for estimation of ions concentration from cutoff frequencies based on observation is also revisited, and N+ concentration is determined. The minimum resonant energy of N+ band is also calculated. This new N+ band is relevant to reduce the discrepancy in mode detection near (Formula presented.) in the observed wave spectrum in order to quantify the transport and energization of N+, in addition to O+, for their relative contribution to the loss and/or scattering mechanisms.