Hybrid-Vlasov modelling of nightside auroral proton precipitation during southward interplanetary magnetic field conditions

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Grandin , M , Battarbee , M , Osmane , A , Ganse , U , Pfau-Kempf , Y , Turc , L , Brito , T , Koskela , T , Dubart , M & Palmroth , M 2019 , ' Hybrid-Vlasov modelling of nightside auroral proton precipitation during southward interplanetary magnetic field conditions ' , Annales Geophysicae , vol. 37 , no. 5 , pp. 791-806 . https://doi.org/10.5194/angeo-37-791-2019

Title: Hybrid-Vlasov modelling of nightside auroral proton precipitation during southward interplanetary magnetic field conditions
Author: Grandin, Maxime; Battarbee, Markus; Osmane, Adnane; Ganse, Urs; Pfau-Kempf, Yann; Turc, Lucile; Brito, Thiago; Koskela, Tuomas; Dubart, Maxime; Palmroth, Minna
Contributor: University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Space Physics Research Group
University of Helsinki, Space Physics Research Group
University of Helsinki, Space Physics Research Group
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Space Physics Research Group
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Space Physics Research Group
University of Helsinki, Doctoral Programme in Particle Physics and Universe Sciences
University of Helsinki, Department of Physics
Date: 2019-09-10
Language: eng
Number of pages: 16
Belongs to series: Annales Geophysicae
ISSN: 0992-7689
URI: http://hdl.handle.net/10138/305638
Abstract: Particle precipitation plays a key role in the coupling of the terrestrial magnetosphere and ionosphere by modifying the upper atmospheric conductivity and chemistry, driving field-aligned currents, and producing aurora. Yet quantitative observations of precipitating fluxes are limited, since ground-based instruments can only provide indirect measurements of precipitation, while particle telescopes aboard spacecraft merely enable point-like in situ observations with an inherently coarse time resolution above a given location. Further, orbit timescales generally prevent the analysis of whole events. On the other hand, global magnetospheric simulations can provide estimations of particle precipitation with a global view and higher time resolution. We present the first results of auroral (similar to 1-30 keV) proton precipitation estimation using the Vlasiator global hybrid-Vlasov model in a noon-midnight meridional plane simulation driven by steady solar wind with a southward interplanetary magnetic field. We first calculate the bounce loss-cone angle value at selected locations in the simulated nightside magnetosphere. Then, using the velocity distribution function representation of the proton population at those selected points, we study the population inside the loss cone. This enables the estimation of differential precipitating number fluxes as would be measured by a particle detector aboard a low-Earth-orbiting (LEO) spacecraft. The obtained differential flux values are in agreement with a well-established empirical model in the midnight sector, as are the integral energy flux and mean precipitating energy. We discuss the time evolution of the precipitation parameters derived in this manner in the global context of nightside magnetospheric activity in this simulation, and we find in particular that precipitation bursts of
Subject: MAGNETOTAIL CURRENT SHEET
PITCH-ANGLE SCATTERING
EARTHWARD FLOW BURSTS
X LINE MOTION
PLASMA SHEET
IONOSPHERIC SIGNATURES
ENERGETIC PROTONS
STATISTICAL-MODEL
RECONNECTION
SIMULATION
115 Astronomy, Space science
114 Physical sciences
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