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Global Distribution of Proton Rings and Associated Magnetosonic Wave Instability in the Inner Magnetosphere
Author(s) -
Yuan Zhigang,
Ouyang Zhihai,
Yu Xiongdong,
Huang Shiyong,
Yao Fei,
Funsten H. O.
Publication year - 2018
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 - 10.1029/2018gl079999
Subject(s) - plasmasphere , physics , magnetosphere , excited state , proton , van allen probes , harmonic , instability , atomic physics , ring current , computational physics , plasma , van allen radiation belt , nuclear physics , mechanics , quantum mechanics
Using the Van Allen Probe‐A observations, we obtained the global distribution of proton rings and calculated the linear wave growth rate of fast magnetosonic (MS) waves in the region L ~3–6. Our statistical and calculated results demonstrate that MS waves can be locally excited on the dayside outside the plasmapause, as well as in the dusk sector inside the plasmapause. The frequency range of unstable MS waves is strongly modulated by the ratio of the proton ring velocity ( V r ) to the local Alfvén speed ( V A ). High harmonic MS waves ( ω > 20Ω H+ ) can be excited outside the plasmapause where V r / V A < 1, while low harmonic MS waves ( ω < 10Ω H+ ) with frequencies less than ~30 Hz are found to be excited both outside and inside the plasmapause where 1 < V r /V A < 2.