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 f low 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 e xcellent for the lowest values of the temperature gradient, there was a substantial discrepancy for the highest value of this gradient. We s how that excellent agreement can be obtained in the latter case as wel l by taking into account the effect of runaway electrons on the heat f low. 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 observation s.