Study of EMIC wave excitation using direct ion measurements

Kyungguk Min; Kaijun Liu; John W Bonnell; Aaron W Breneman; Richard E Denton; Herbert O Funsten; Jöerg‐Micha Jahn; Craig A Kletzing; William S Kurth; Brian A Larsen; Geoffrey D Reeves; Harlan E Spence; John R Wygant

doi:10.1002/2014JA020717

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Study of EMIC wave excitation using direct ion measurements

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Study of EMIC wave excitation using direct ion measurements

Kyungguk Min, Kaijun Liu, John W Bonnell, Aaron W Breneman, Richard E Denton, Herbert O Funsten, Jöerg‐Micha Jahn, Craig A Kletzing, William S Kurth, Brian A Larsen, …

Journal of geophysical research. Space physics, Vol.120(4), pp.2702-2719

04/2015

DOI: 10.1002/2014JA020717

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Abstract

With data from Van Allen Probes, we investigate electromagnetic ion cyclotron (EMIC) wave excitation using simultaneously observed ion distributions. Strong He band waves occurred while the spacecraft was moving through an enhanced density region. We extract from helium, oxygen, proton, and electron mass spectrometer measurement the velocity distributions of warm heavy ions as well as anisotropic energetic protons that drive wave growth through the ion cyclotron instability. Fitting the measured ion fluxes to multiple sinm‐type distribution functions, we find that the observed ions make up about 15% of the total ions, but about 85% of them are still missing. By making legitimate estimates of the unseen cold (below ∼2 eV) ion composition from cutoff frequencies suggested by the observed wave spectrum, a series of linear instability analyses and hybrid simulations are carried out. The simulated waves generally vary as predicted by linear theory. They are more sensitive to the cold O+ concentration than the cold He+ concentration. Increasing the cold O+ concentration weakens the He band waves but enhances the O band waves. Finally, the exact cold ion composition is suggested to be in a range when the simulated wave spectrum best matches the observed one. Key Points Study of EMIC wave excitation using directly measured ion measurements Integrated analysis of observation, linear theory, and hybrid simulations

EMIC wave excitation

observation, linear theory and hybrid simulation

Details

Title: Subtitle: Study of EMIC wave excitation using direct ion measurements
Creators: Kyungguk Min - Auburn University
Kaijun Liu - Auburn University
John W Bonnell - University of California, Berkeley
Aaron W Breneman - University of Minnesota
Richard E Denton - Dartmouth College
Herbert O Funsten - Los Alamos National Laboratory
Jöerg‐Micha Jahn - Space Science Department
Craig A Kletzing - University of Iowa
William S Kurth - University of Iowa
Brian A Larsen - Los Alamos National Laboratory
Geoffrey D Reeves - Los Alamos National Laboratory
Harlan E Spence - University of New Hampshire
John R Wygant - University of Minnesota
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.120(4), pp.2702-2719
DOI: 10.1002/2014JA020717
ISSN: 2169-9380
eISSN: 2169-9402
Number of pages: 18
Grant note: NSF (1303623) NASA High‐End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center NASA (NNX13AD62G; NNX13AD65G; NNX08AM58G) RBSP‐ECT JHU/APL contract 967399 under NASA's prime contract NAS5‐01072
Language: English
Date published: 04/2015
Academic Unit: Physics and Astronomy
Record Identifier: 9984199830102771

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