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New chorus wave properties near the equator from Van Allen Probes wave observations
Author(s) -
Li W.,
Santolik O.,
Bortnik J.,
Thorne R. M.,
Kletzing C. A.,
Kurth W. S.,
Hospodarsky G. B.
Publication year - 2016
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 - 10.1002/2016gl068780
Subject(s) - chorus , magnetosphere , physics , van allen probes , mode (computer interface) , earth's magnetic field , computational physics , equator , schumann resonances , resonance (particle physics) , normal mode , geomagnetic storm , geophysics , ionosphere , van allen radiation belt , atomic physics , magnetic field , latitude , astronomy , acoustics , quantum mechanics , art , literature , computer science , vibration , operating system
Abstract The chorus wave properties are evaluated using Van Allen Probes data in the Earth's equatorial magnetosphere. Two distinct modes of lower band chorus are identified: a quasi‐parallel mode and a quasi‐electrostatic mode, whose wave normal direction is close to the resonance cone. Statistical results indicate that the quasi‐electrostatic (quasi‐parallel) mode preferentially occurs during relatively quiet (disturbed) geomagnetic activity at lower (higher) L shells. Although the magnetic intensity of the quasi‐electrostatic mode is considerably weaker than the quasi‐parallel mode, their electric intensities are comparable. A newly identified feature of the quasi‐electrostatic mode is that its frequency peaks at higher values compared to the quasi‐parallel mode that exhibits a broad frequency spectrum. Moreover, upper band chorus wave normal directions vary between 0° and the resonance cone and become more parallel as geomagnetic activity increases. Our new findings suggest that chorus‐driven energetic electron dynamics needs a careful examination by considering the properties of these two distinct modes.