Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation

In August 2015, the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) observed precipitation of energetic (<200 keV) electrons magnetically conjugate to a region of dense cold plasma as measured by the twin Van Allen Probes spacecraft. The two spacecraft passed through th...

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Autores principales:	R. M. Millan, J.-F. Ripoll, O. Santolík, W. S. Kurth
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	radiation belt wave-particle interaction electron precipitation plasmaspheric plume whistler-mode hiss/chorus quasi-linear diffusion Astronomy QB1-991 Geophysics. Cosmic physics QC801-809
Acceso en línea:	https://doaj.org/article/26d1a585b71643e98fda97977ea61757
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spelling	oai:doaj.org-article:26d1a585b71643e98fda97977ea617572021-12-02T10:31:19ZEarly-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation2296-987X10.3389/fspas.2021.776992https://doaj.org/article/26d1a585b71643e98fda97977ea617572021-12-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fspas.2021.776992/fullhttps://doaj.org/toc/2296-987XIn August 2015, the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) observed precipitation of energetic (<200 keV) electrons magnetically conjugate to a region of dense cold plasma as measured by the twin Van Allen Probes spacecraft. The two spacecraft passed through the high density region during multiple orbits, showing that the structure was spatial and relatively stable over many hours. The region, identified as a plasmaspheric plume, was filled with intense hiss-like plasma waves. We use a quasi-linear diffusion model to investigate plume whistler-mode hiss waves as the cause of precipitation observed by BARREL. The model input parameters are based on the observed wave, plasma and energetic particle properties obtained from Van Allen Probes. Diffusion coefficients are found to be largest in the same energy range as the precipitation observed by BARREL, indicating that the plume hiss waves were responsible for the precipitation. The event-driven pitch angle diffusion simulation is also used to investigate the evolution of the electron phase space density (PSD) for different energies and assumed initial pitch angle distributions. The results show a complex temporal evolution of the phase space density, with periods of both growth and loss. The earliest dynamics, within the ∼5 first minutes, can be controlled by a growth of the PSD near the loss cone (by a factor up to ∼2, depending on the conditions, pitch angle, and energy), favored by the absence of a gradient at the loss cone and by the gradients of the initial pitch angle distribution. Global loss by 1-3 orders of magnitude (depending on the energy) occurs within the first ∼100 min of wave-particle interaction. The prevalence of plasmaspheric plumes and detached plasma regions suggests whistler-mode hiss waves could be an important driver of electron loss even at high L-value (L ∼6), outside of the main plasmasphere.R. M. MillanJ.-F. RipollJ.-F. RipollO. SantolíkO. SantolíkW. S. KurthFrontiers Media S.A.articleradiation beltwave-particle interactionelectron precipitationplasmaspheric plumewhistler-mode hiss/chorusquasi-linear diffusionAstronomyQB1-991Geophysics. Cosmic physicsQC801-809ENFrontiers in Astronomy and Space Sciences, Vol 8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	radiation belt wave-particle interaction electron precipitation plasmaspheric plume whistler-mode hiss/chorus quasi-linear diffusion Astronomy QB1-991 Geophysics. Cosmic physics QC801-809
spellingShingle	radiation belt wave-particle interaction electron precipitation plasmaspheric plume whistler-mode hiss/chorus quasi-linear diffusion Astronomy QB1-991 Geophysics. Cosmic physics QC801-809 R. M. Millan J.-F. Ripoll J.-F. Ripoll O. Santolík O. Santolík W. S. Kurth Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation
description	In August 2015, the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) observed precipitation of energetic (<200 keV) electrons magnetically conjugate to a region of dense cold plasma as measured by the twin Van Allen Probes spacecraft. The two spacecraft passed through the high density region during multiple orbits, showing that the structure was spatial and relatively stable over many hours. The region, identified as a plasmaspheric plume, was filled with intense hiss-like plasma waves. We use a quasi-linear diffusion model to investigate plume whistler-mode hiss waves as the cause of precipitation observed by BARREL. The model input parameters are based on the observed wave, plasma and energetic particle properties obtained from Van Allen Probes. Diffusion coefficients are found to be largest in the same energy range as the precipitation observed by BARREL, indicating that the plume hiss waves were responsible for the precipitation. The event-driven pitch angle diffusion simulation is also used to investigate the evolution of the electron phase space density (PSD) for different energies and assumed initial pitch angle distributions. The results show a complex temporal evolution of the phase space density, with periods of both growth and loss. The earliest dynamics, within the ∼5 first minutes, can be controlled by a growth of the PSD near the loss cone (by a factor up to ∼2, depending on the conditions, pitch angle, and energy), favored by the absence of a gradient at the loss cone and by the gradients of the initial pitch angle distribution. Global loss by 1-3 orders of magnitude (depending on the energy) occurs within the first ∼100 min of wave-particle interaction. The prevalence of plasmaspheric plumes and detached plasma regions suggests whistler-mode hiss waves could be an important driver of electron loss even at high L-value (L ∼6), outside of the main plasmasphere.
format	article
author	R. M. Millan J.-F. Ripoll J.-F. Ripoll O. Santolík O. Santolík W. S. Kurth
author_facet	R. M. Millan J.-F. Ripoll J.-F. Ripoll O. Santolík O. Santolík W. S. Kurth
author_sort	R. M. Millan
title	Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation
title_short	Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation
title_full	Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation
title_fullStr	Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation
title_full_unstemmed	Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation
title_sort	early-time non-equilibrium pitch angle diffusion of electrons by whistler-mode hiss in a plasmaspheric plume associated with barrel precipitation
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/26d1a585b71643e98fda97977ea61757
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Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation

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