Diagnosing radio plasma heating in the polar summer mesosphere using cross modulation: Theory and observations

Abstract

Radio heating of the free electrons in the mesosphere is an important diagnostic technique for the phenomenon of polar mesosphere summer echoes (PMSE). Due to a lack of suitable observations, the heating must be modeled when studying its effect on PMSE. In order to try to validate these models, the cross-modulation technique was implemented at the EISCAT facility near Troms, Norway to compare the absorption of a diagnostic radio wave in the heated and unheated plasma. The results are compared to predictions from a model similar to that used for estimating the heating in PMSE studies. It is found that, after allowing for certain instrumental effects, the model overestimates the change in absorption of the diagnostic wave by a factor of 1.5-2.5. It is suggested that the assumption that the electron distribution function remains Maxwellian during heating could contribute to this discrepancy. Copyright 2010 by the American Geophysical Union.