The electron energy distribution during HF pumping, a picture painted with all colors

Abstract

The shape of the electron energy distribution has long been a central question in the field of high-frequency radio-induced optical emission experiments. This report presents estimates of the electron energy distribution function, fe(E), from 0 to 60eV, based on optical multiwavelength (6300, 5577, 8446, 4278 Å) data and 930-MHz incoherent scatter radar measurements of ion temperature, electron temperature and electron concentration. According to our estimate, the electron energy distribution has a depression at around 2eV, probably caused by electron excitation of vibrational states in N2, and a high energy tail that is clearly supra-thermal. The temporal evolution of the emissions indicates that the electron temperature still plays an important role in providing electrons with energies close to 2eV. At the higher energies the electron energy distribution has a non-thermal tail. © European Geosciences Union 2005.