FIRST EISCAT OBSERVATIONS OF THE MODIFICATION OF F-REGION ELECTRON TEMPERATURES DURING RP HEATING AT HARMONICS OF THE ELECTRON GYRO FREQUENCY

Results are presented from recent ionospheric F-region modification ex periments in which the heater induced anomalous absorption and electro n temperature changes were measured for a variety of heater frequencie s which included the third and fourth harmonics of the electron gyro f requencies. The results indicate that there are strong minima in the r esponses of both anomalous absorption and electron heating in the vici nity of the two harmonic frequencies. These new observations provide e vidence for the view that anomalous electron heating in the presence o f small scale field aligned plasma irregularities dominates over colli sional heating at high latitudes.