Collisional electrostatic ion cyclotron waves as a possible source of energetic heavy ions in the magnetosphere

A new mechanism is proposed for the source of energetic heavy ions (NO+, O2+, and O+) found in the magnetosphere. Simulations using a multispecies particle simulation code for resistive current-driven electrostatic ion cyclotron waves show transverse and parallel bulk heating of bottomside ionospheric NO+, O2+ and O+ ion populations. The dominant mechanism for the transverse bulk heating is resonant ion heating by wave-particle ion trapping. Using a linear kinetic dispersion relation for a magnetized, collisional, homogeneous, and multi-ion plasma, it is found that collisional electrostatic ion cyclotron waves near the NO+, O2+, and O+ gyrofrequencies are unstable to field-aligned currents of 50 μ A/m2 for a typical bottomside ionosphere (<300 km altitude). A simple ion outflow model of heavy ions is formulated that verifies the assertion that a large number of energetic heavy ions originating from below 250 km can reach the topside ionosphere (> 1000 km), and then via parallel electric fields be ejected into the Earth's magnetosphere