6300-A intensity variations produced by the Arecibo ionospheric modification experiment

Nightglow 6300-Å intensity suppression and enhancement transients have been observed in conjunction with heating of the F region ionospheric electrons in Arecibo ionospheric modification experiments (IME). Ohmic heating of the electrons during X mode propagation of the heating wave results in a ∼1.3% suppression of intensity, in semiquantitative agreement with the suppression predicted for ΔTe ≃ 130°K (measured by the backscatter radar). The 6300-Å intensity enhancements (∼6 R) associated with O mode propagation of the heating wave are far too large to be produced by ohmic heating (a value ΔTe ∼ 900°K, about 5 times larger than the backscatter measured value, would be required), suggesting electron acceleration by strong plasma waves that are generated by the heating RF wave. The O(¹D) lifetimes determined from the time constants of the 6300-Å intensity enhancement transients yield an F region quenching coefficient k(N2) ≃ 6 to 8 × 10−11 cm³/s, in good agreement with the Platteville IME and with laboratory results.