Hybrid-Vlasov simulation of auroral proton precipitation in the cusps : Comparison of northward and southward interplanetary magnetic field driving

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Grandin , M , Turc , L , Battarbee , M , Ganse , U , Johlander , A , Pfau-Kempf , Y , Dubart , M & Palmroth , M 2020 , ' Hybrid-Vlasov simulation of auroral proton precipitation in the cusps : Comparison of northward and southward interplanetary magnetic field driving ' , Journal of space weather and space climate , vol. 10 , 51 . https://doi.org/10.1051/swsc/2020053

Title: Hybrid-Vlasov simulation of auroral proton precipitation in the cusps : Comparison of northward and southward interplanetary magnetic field driving
Author: Grandin, Maxime; Turc, Lucile; Battarbee, Markus; Ganse, Urs; Johlander, Andreas; Pfau-Kempf, Yann; 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, Department of Physics
University of Helsinki, Space Physics Research Group
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Space Physics Research Group
University of Helsinki, Department of Physics
Date: 2020-10-14
Language: eng
Number of pages: 17
Belongs to series: Journal of space weather and space climate
ISSN: 2115-7251
URI: http://hdl.handle.net/10138/321542
Abstract: Particle precipitation is a central aspect of space weather, as it strongly couples the magnetosphere and the ionosphere and can be responsible for radio signal disruption at high latitudes. We present the first hybrid-Vlasov simulations of proton precipitation in the polar cusps. We use two runs from the Vlasiator model to compare cusp proton precipitation fluxes during southward and northward interplanetary magnetic field (IMF) driving. The simulations reproduce well-known features of cusp precipitation, such as a reverse dispersion of precipitating proton energies, with proton energies increasing with increasing geomagnetic latitude under northward IMF driving, and a nonreversed dispersion under southward IMF driving. The cusp is also found more polewards in the northward IMF simulation than in the southward IMF simulation. In addition, we find that the bursty precipitation during southward IMF driving is associated with the transit of flux transfer events in the vicinity of the cusp. In the northward IMF simulation, dual lobe reconnection takes place. As a consequence, in addition to the high-latitude precipitation spot associated with the lobe reconnection from the same hemisphere, we observe lower-latitude precipitating protons which originate from the opposite hemisphere's lobe reconnection site. The proton velocity distribution functions along the newly closed dayside magnetic field lines exhibit multiple proton beams travelling parallel and antiparallel to the magnetic field direction, which is consistent with previously reported observations with the Cluster spacecraft. In both runs, clear electromagnetic ion cyclotron waves are generated in the cusps and might further increase the calculated precipitating fluxes by scattering protons to the loss cone in the low-altitude cusp. Global kinetic simulations can improve the understanding of space weather by providing a detailed physical description of the entire near-Earth space and its internal couplings.
Subject: polar cusp
particle precipitation
numerical simulations
magnetosphere
EMIC waves
X LINE MOTION
MIDALTITUDE CUSP
FLUX-TRANSFER
STATISTICAL-MODEL
ION-ACCELERATION
PLASMA INJECTION
CLUSTER MISSION
IMF
RECONNECTION
SIGNATURES
114 Physical sciences
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