Abstract
Equatorial electromagnetic ELF emissions at a frequency range around the oxygen ion gyrofrequency were observed in the low altitude plasmasphere (L = 1.5∼2.5) during magnetic storms with high activity of the ring current by triaxial search coil and single component electric field instruments on board the Akebono satellite. We find that a particular type of the ELF emissions occur with a multi‐band spectral structure around the local gyrofrequency (Fo+) of the oxygen ion (O+) during the main phase of magnetic storm. Our finding includes the following; The multi‐band emissions are localized in the morning sector and often consist of several spaced frequency bands closely related the local gyro‐harmonics of oxygen ion (O+) with a fundamental frequency of Fo+ or 2Fo+. The frequency of each band is dependent on the local magnetic field variation along the satellite orbit and the spacing between the bands is almost equal to Fo+ or 2Fo+. It is suggested that emissions are generated by terrestrial oxygen ion composing the ring current area during the main phase of magnetic storm.
Published Version
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