First EISCAT observations of the modification of F-region electron temperatures during RF heating at harmonics of the electron gyro frequency

Abstract

Results are presented from recent ionospheric F-region modification experiments in which the heater induced anomalous absorption and electron temperature changes were measured for a variety of heater frequencies which included the third and fourth harmonics of the electron gyro frequencies. The results indicate that there are strong minima in the responses of both anomalous absorption and electron heating in the vicinity of the two harmonic frequencies. These new observations provide evidence for the view that anomalous electron heating in the presence of small scale field aligned plasma irregularities dominates over collisional heating at high latitudes.