Atomic and molecular ion temperatures and ion temperature anisotropy in the auroral F region in the presence of large electric fields

Abstract

The atomic O+ ion oxygen and molecular NO+ ion nitrogen temperatures and temperature anisotropy throughout a realistic auroral F region in the presence of large electric fields are studied. The O+ ion temperature is smaller than the NO+ ion temperature in the lower part of the F region, and this effect increases with the increasing of the neutral temperature as well as of the ion‐neutral drift velocity. The ion temperature anisotropy is defined as the ratio of the ion perpendicular temperature to the ion parallel temperature with respect to the magnetic field. For the O+ ions this ratio is maximum around 290 km in altitude for a constant ion‐neutral drift velocity throughout the F region. For similar conditions the NO+ ion temperature anisotropy is constant between 175 km and 250 km in altitude and decreases for higher altitudes. Application to mixed species non‐Maxwellian radar spectra analysis is discussed.