Séminaire IPAG

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Investigating particle precipitation in a citizen science project and in global hybrid-Vlasov simulations

jeudi 10 novembre 2022 - 11h00

Maxime Grandin - University of Helsinki
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This seminar will consist of two parts, both of which are related to the precipitation of charged particles from near-Earth space into the ionosphere. The first part will present the most recent results on the so-called dune aurora, which is a new auroral form discovered thanks to a collaboration between researchers and Finnish citizen scientists chasing the northern light. These "dunes" consist in a spatial modulation of the diffuse and faint green aurora into parallel stripes separated from each other by a few tens of kilometres. They have been observed equatorwards from the main auroral arc during evening hours associated with geomagnetically disturbed conditions, and they have been mapped to an altitude of about 100 km. While the discovery study hypothesised that the auroral emission intensity modulation within the dunes might be due to the presence of an atmospheric wave called a mesospheric bore, there had not yet been any confirmation that they were intrinsically an auroral phenomenon resulting from particle precipitation into the upper atmosphere. In out latest paper, we reported the study of a large-scale dune aurora event which spanned from Finland to Scotland. Combining observations from Finnish, Norwegian and Scottish citizen scientists with satellite measurements, we confirmed that there was electron precipitation in the region where the dunes were seen and that atmospheric conditions were unusual at mesospheric altitudes, possibly revealing the presence of a mesospheric bore. In the second part, we will talk about numerical simulations of auroral proton precipitation using the Vlasiator model. Vlasiator enables global simulations of near-Earth space using the hybrid-Vlasov approach, in which the protons are described through their velocity distribution function and electrons are treated as a massless charge-neutralising fluid. We will briefly review a few results on proton precipitation in the first 3D Vlasiator run, under southward interplanetary magnetic field driving.

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Hôtes : Mathieu Barthelemy

Salle Manuel Forestini, 414 rue de la piscine, 38400 Saint Martin d'Hères