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The Effect of Hot Protons on Magnetosonic Waves Inside and Outside the Plasmapause: New Observations and Theoretic Results
Author(s) -
Liu Bin,
Li Liuyuan,
Yu Jiang,
Cao Jinbin
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024676
Subject(s) - plasmasphere , physics , proton , plasma , magnetosphere , lower hybrid oscillation , computational physics , atomic physics , resonance (particle physics) , nuclear physics , cyclotron
Abstract Based on the wave and proton observations by Van Allen Probes A and B, we examined the effects of hot protons (0.01–50 keV) on fast magnetosonic (MS) waves inside and outside the Earth's plasmasphere. In the low‐density plasma trough outside the plasmapause, the gyroresonance interactions between hot protons and MS waves not only cause the MS wave growth at some frequencies but also lead to the damping of MS waves at other frequencies, which depends on the proton phase space density gradient and the ambient plasma density. The gyroresonance of the observed hot protons cannot excite MS waves near the lower hybrid resonance frequency and even causes the MS wave damping. Thus, the frequencies of the observed MS waves outside the plasmapause are usually lower than the lower hybrid resonance frequency. In the high‐density plasmasphere, the observed hot protons merely lead to the weak gyrodamping of MS waves. The persistent existence of lower band MS waves indicates that the weak gyrodamping effect of hot protons on MS waves is ignorable in the high‐density plasmasphere.