ON HEAT-FLOW CONTRIBUTION TO PLASMA LINE FREQUENCY IN THE F-REGION

It was recently shown by Kofman et al. (1993), that an electron heat flow correction is essential in interpreting the difference between the frequency of upshifted and downshifted electron plasma lines. However, whereas the agreement with the frequency difference correction was excellent for the lowest values of the temperature gradient, there was a substantial discrepancy for the highest value of this gradient. We show that excellent agreement can be obtained in the latter case as well by taking into account the effect of runaway electrons on the heat flow. It is suggested that a proper account of the heat flow including the correction for runaways may make it possible to reliably determine the field aligned currents from incoherent scatter radars observations.