Oxygen cyclotron harmonic waves observed by the Van Allen Probes

TitleOxygen cyclotron harmonic waves observed by the Van Allen Probes
Publication TypeJournal Article
Year of Publication2017
AuthorsXiongdong, Y, Zhigang, Y, Dedong, W, Shiyong, H, Haimeng, L, Tao, Y, Zheng, Q
JournalScience China: Earth Sciences
Date Published03/2017
KeywordsOxygen Cyclotron Harmonic Waves; Radiation belt; Ring current ions; Van Allen Probes
AbstractFine structured multiple-harmonic electromagnetic emissions at frequencies around the equatorial oxygen cyclotron harmonics are observed by Van Allen Probe A outside the core plasmasphere (L~5) off the magnetic equator (MLAT~-7.5°) during a magnetic storm. We find that the multiple-harmonic emissions have their PSD peaks at 2~8 equatorial oxygen gyro-harmonics (f~nfO+, n=2~8) while the fundamental mode (n=1) is absent, implying that the harmonic waves are generated near the equator and propagate into the observation region. Additionally these electromagnetic emissions are linear polarized. Different from the equatorial noise emission propagating very obliquely, these emissions have moderate wave normal angles (about 40°~60°) which predominately become larger as the harmonic number increases. Considering their frequency and wave normal angle characteristics, it is suggested that these multiple-harmonic emissions might play an important role in the dynamic variation of radiation belt electrons.

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