New chorus wave properties near the equator from Van Allen Probes wave observations

W Li; O Santolik; C. A Kletzing; J Bortnik; W. S Kurth; R. M Thorne; G. B Hospodarsky

doi:10.1002/2016GL068780

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New chorus wave properties near the equator from Van Allen Probes wave observations

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New chorus wave properties near the equator from Van Allen Probes wave observations

W Li, O Santolik, C. A Kletzing, J Bortnik, W. S Kurth, R. M Thorne and G. B Hospodarsky

Geophysical research letters, Vol.43(10), pp.4725-4735

05/28/2016

DOI: 10.1002/2016GL068780

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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. Key Points Chorus wave normal and spectral properties are evaluated using Van Allen Probes wave data Lower band chorus has two distinct modes: a quasi‐parallel mode and a quasi‐electrostatic mode Quasi‐electrostatic chorus occurs preferentially during quiet times, at lower L, and in higher frequencies

chorus wave

oblique

quasi‐electrostatic

quasi‐parallel

wave normal angles

Details

Title: Subtitle: New chorus wave properties near the equator from Van Allen Probes wave observations
Creators: W Li - University of California, Los Angeles
O Santolik - Charles University
C. A Kletzing - University of Iowa
J Bortnik - University of California, Los Angeles
W. S Kurth - University of Iowa
R. M Thorne - University of California, Los Angeles
G. B Hospodarsky - University of Iowa
Resource Type: Journal article
Publication Details: Geophysical research letters, Vol.43(10), pp.4725-4735
DOI: 10.1002/2016GL068780
ISSN: 0094-8276
eISSN: 1944-8007
Number of pages: 11
Grant note: RBSP‐EMFISIS JHU/APL (921647) AFOSR (FA9550‐15‐1‐0158) NSF (1405054; 1564510; PLR 1341359) NASA (NNX15AF61G; NNX15AI96G; NNX11AR64G; NNX13AI61G; NNX14AI18G) NASA's prime (NAS5‐01072)
Language: English
Date published: 05/28/2016
Academic Unit: Physics and Astronomy
Record Identifier: 9984199749602771

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