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First observations of minority ion (H + ) structuring in stimulated radiation during second electron gyroharmonic heating experiments
Author(s) -
Bordikar M. R.,
Scales W. A.,
Samimi A. R.,
Bernhardt P. A.,
Brizcinski S.,
McCarrick M. J.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50327
Subject(s) - ionosphere , physics , ion , atomic physics , electron precipitation , proton , electron , plasma , radiation , nuclear physics , magnetosphere , geophysics , quantum mechanics
This work presents the first observations of unique narrowband emissions ordered near the hydrogen ion (H + ) gyrofrequency ( f c H ) in the stimulated electromagnetic emission spectrum when the transmitter is tuned near the second electron gyroharmonic frequency (2 f c e ) during ionospheric modification experiments. The frequency structuring of these newly discovered emission lines is quite unexpected since H + is known to be a minor constituent in the interaction region which is near 160 km altitude. The spectral lines are typically shifted from the pump wave frequency by harmonics of a frequency about 10% less than f c H (≈ 800 Hz) and have a bandwidth of less than 50 Hz which is near the O + gyrofrequency f c O . A theory is proposed to explain these emissions in terms of a parametric decay instability in a multi‐ion species plasma due to possible proton precipitation associated with the disturbed conditions during the heating experiment. The observations can be explained by including several percent H + ions into the background plasma. The implications are new possibilities for characterizing proton precipitation events during ionospheric heating experiments.