Reinterpretation of the 6300‐Å airglow enhancements observed in ionosphere heating experiments based on analysis of Platteville, Colorado, data

Abstract

Airglow enhancement observations have been considered as supporting evidence of electron acceleration in ionosphere heating experiments by high‐power HF waves. Here we analyze some of the 6300‐Å airglow data from the Platteville, Colorado, heating experiments of 1970, employing new electron impact excitation rates for the O(1D) state and empirical, but in accord with experimental and theoretical constraints, plasma heating rates and show that these airglow enhancements should be attributed to excitation by thermal electrons. An important aspect of the present analysis is the excellent agreement of the observed and the calculated airglow enhancements over several complete transmitter on/off cycles of several minutes duration and an increasing airglow trend of 1 hour duration. The fact that the OI red line may be thermally excited and the scarcity of observations of simultaneous OI red and green line enhancements imply that electron acceleration, even to a few eV, may require very special experimental and ionospheric conditions that are not very often realized.