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Application of Cold and Hot Plasma Composition Measurements to Investigate Impacts on Dusk-Side Electromagnetic Ion Cyclotron Waves.

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Title:	Application of Cold and Hot Plasma Composition Measurements to Investigate Impacts on Dusk-Side Electromagnetic Ion Cyclotron Waves.
Authors:	Lee, Justin H.¹ justin.h.lee@aero.org, Turner, Drew L.², Vines, Sarah K.², Allen, Robert C.², Toledo-Redondo, Sergio³, Bingham, Sam T.², Fuselier, Stephen A.^4,5, Cohen, Ian J.², Starkey, Michael J.^4,5, Graham, Daniel B.⁶, Khotyaintsev, Yuri V.⁶, Mauk, Barry H.², Pollock, Craig J.⁷, Ergun, Robert E.⁸, Lindqvist, Per-Arne⁹, Torbert, Roy B.¹⁰, Burch, James L.⁴
Source:	Journal of Geophysical Research. Space Physics. Jan2021, Vol. 126 Issue 1, p1-22. 22p.
Subject Terms:	Plasma waves, Electromagnetic fields, Electromagnetic waves, Magnetosphere, Cyclotron resonance
Abstract:	An extended interval of perturbed magnetospheric conditions in November 2016 supported increased convection and sunward transport of plasmaspheric material. During this period of time the Magnetospheric Multiscale satellites, with their apogees along Earth's dusk-side outer magnetosphere, encountered several cold plasma density structures at the same time as plasma bulk flows capable of accelerating hidden cold plasma occurred. Investigating the charged particle and fields data during two subintervals showed that the satellites made direct measurements of cold plasmaspheric ions embedded within multicomponent hot plasmas as well as electromagnetic emissions consistent with electromagnetic ion cyclotron (EMIC) waves. The complex in situ ion composition measurements were applied to linear wave modeling to interpret the impacts of cold and hot ion species on wave growth and band structure. Although the waves for both intervals were predicted to have peak growth rate below ûHe+, substantial differences were observed among all other dispersive properties. The modeling also showed EMIC waves generated in the presence of heavy ions had growth rates and unstable wave numbers always smaller than predicted for a pure proton-electron plasma. The results provide implications for future investigation of EMIC wave generation with and without direct measurements of the cold and hot plasma composition as well as of subsequent wave-particle interactions. Plain Language Summary Electromagnetic ion cyclotron (EMIC) waves occur throughout our solar system. The waves have been observed near Earth and are more likely to achieve large amplitudes in the magnetized plasma that exists in a region of space called Earth's dusk-side magnetosphere. Multiple plasma populations exist in this region that can be organized into groups of cold or hot plasmas. Although the hot plasmas can be measured most of the time, the cold plasmas are usually hidden from plasma sensors due to positive spacecraft charging issues; cold plasmas are therefore usually unavailable to help provide a detailed understanding of why dusk-side EMIC waves are generated. The purpose of our study was to investigate measurements made by the NASA Magnetospheric Multiscale satellites to during a time period when the cold plasma species were not hidden and apply these measurements to improve understanding of these dusk-side EMIC waves. The results showed why comprehensive measurements are needed to continue advancing our understanding of EMIC waves as seen by other spacecraft in different regions in Earth's magnetosphere, and how these waves impact other plasma populations. [ABSTRACT FROM AUTHOR]
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Abstract:	An extended interval of perturbed magnetospheric conditions in November 2016 supported increased convection and sunward transport of plasmaspheric material. During this period of time the Magnetospheric Multiscale satellites, with their apogees along Earth's dusk-side outer magnetosphere, encountered several cold plasma density structures at the same time as plasma bulk flows capable of accelerating hidden cold plasma occurred. Investigating the charged particle and fields data during two subintervals showed that the satellites made direct measurements of cold plasmaspheric ions embedded within multicomponent hot plasmas as well as electromagnetic emissions consistent with electromagnetic ion cyclotron (EMIC) waves. The complex in situ ion composition measurements were applied to linear wave modeling to interpret the impacts of cold and hot ion species on wave growth and band structure. Although the waves for both intervals were predicted to have peak growth rate below ûHe+, substantial differences were observed among all other dispersive properties. The modeling also showed EMIC waves generated in the presence of heavy ions had growth rates and unstable wave numbers always smaller than predicted for a pure proton-electron plasma. The results provide implications for future investigation of EMIC wave generation with and without direct measurements of the cold and hot plasma composition as well as of subsequent wave-particle interactions. Plain Language Summary Electromagnetic ion cyclotron (EMIC) waves occur throughout our solar system. The waves have been observed near Earth and are more likely to achieve large amplitudes in the magnetized plasma that exists in a region of space called Earth's dusk-side magnetosphere. Multiple plasma populations exist in this region that can be organized into groups of cold or hot plasmas. Although the hot plasmas can be measured most of the time, the cold plasmas are usually hidden from plasma sensors due to positive spacecraft charging issues; cold plasmas are therefore usually unavailable to help provide a detailed understanding of why dusk-side EMIC waves are generated. The purpose of our study was to investigate measurements made by the NASA Magnetospheric Multiscale satellites to during a time period when the cold plasma species were not hidden and apply these measurements to improve understanding of these dusk-side EMIC waves. The results showed why comprehensive measurements are needed to continue advancing our understanding of EMIC waves as seen by other spacecraft in different regions in Earth's magnetosphere, and how these waves impact other plasma populations. [ABSTRACT FROM AUTHOR]
ISSN:	21699380
DOI:	10.1029/2020JA028650