The Relationship Between EMIC Wave Properties and Proton Distributions Based on Van Allen Probes Observations

Authors

Chao Yue, University of California, Los Angeles
Chae Woo Jun, University of California, Los Angeles
Jacob Bortnik, University of California, Los Angeles
Xin An, University of California, Los Angeles
Qianli Ma, University of California, Los Angeles
Geoffrey D. Reeves, Los Alamos National Laboratory
Harlan E. Spence, University of New Hampshire Durham
Andrew J. Gerrard, New Jersey Institute of Technology
Matina Gkioulidou, Johns Hopkins University Applied Physics Laboratory
Donald G. Mitchell, Johns Hopkins University Applied Physics Laboratory
Craig A. Kletzing, University of Iowa

Document Type

Article

Publication Date

4-28-2019

Abstract

Plasma kinetic theory predicts that sufficiently anisotropic proton distribution will excite electromagnetic ion cyclotron (EMIC) waves, which in turn relax the proton distribution to a marginally stable state creating an upper bound on the relaxed proton anisotropy. Here, using EMIC wave observations and coincident plasma measurements made by Van Allen Probes in the inner magnetosphere, we show that the proton distributions are well constrained by this instability to a marginally stable state. Near the threshold, the probability of EMIC wave occurrence is highest, having left-handed polarization and observed near the magnetic equator with relatively small wave normal angles, indicating that these waves are locally generated. In addition, EMIC waves are distributed in two magnetic local time regions with different intensity. Compared with helium band waves, hydrogen band waves behave similarly except that they are often observed in low-density regions. These results reveal several important features regarding EMIC waves excitation and propagation.

Identifier

85064705316 (Scopus)

Publication Title

Geophysical Research Letters

External Full Text Location

https://doi.org/10.1029/2019GL082633

e-ISSN

19448007

ISSN

00948276

First Page

4070

Last Page

4078

Issue

8

Volume

46

Grant

NASA HTIDeS NNX16AG21G

Fund Ref

Goddard Space Flight Center

Recommended Citation

Yue, Chao; Jun, Chae Woo; Bortnik, Jacob; An, Xin; Ma, Qianli; Reeves, Geoffrey D.; Spence, Harlan E.; Gerrard, Andrew J.; Gkioulidou, Matina; Mitchell, Donald G.; and Kletzing, Craig A., "The Relationship Between EMIC Wave Properties and Proton Distributions Based on Van Allen Probes Observations" (2019). Faculty Publications. 7651.
https://digitalcommons.njit.edu/fac_pubs/7651