Satellite Ionosonde Records: Resonances Below the Cyclotron Frequency

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Science  12 Apr 1968:
Vol. 160, Issue 3824, pp. 181-184
DOI: 10.1126/science.160.3824.181


Resonant responses observed by the topside ionosonde in the Canadian satellite Alouette II are examined. In addition to the well-known plasma resonances, several subsidiary resonances are identified below the electron cyclotron frequency. Their patterns of occurrence are not consistent with a suggested explanation of induced magnetic dipole radiation; rather they appear to result from harmonic stimulation of the plasma resonances and beat-frequency generation.