Communication Dans Un Congrès Année : 2023

Unveiling the electron kinetic physics at Mercury using global numerical simulations

Résumé

Mercury has a relatively weak intrinsic magnetic field that forms a small Earth-like magnetosphere. The magnetosphere of Mercury hosts strongly dynamical and nonlinear phenomena governed by kinetic plasma physics. Until now, the plasma dynamics at Mercury was addressed using fluid (MHD, multifluid), hybrid (kinetic ions and fluid massless electrons) and test particle (particles moving in fixed electromagnetic fields) plasma models. These models provided a good understanding of the large-scale magnetospheric structure, of the ion kinetic physics at Mercury, and of the first-order particle motion in prescribed magnetospheric fields. But, they lacked a self-consistent treatment of the kinetic physics of electrons. Now, the computational power of HPC facilities enables us to run global, fully-kinetic simulations of a "small" magnetosphere, such as the one of Mercury, including self-consistently the kinetic physics of both ions and electrons. With such novel simulations, we address unsolved problems related to the kinetic physics of electrons in Mercury's magnetosphere. In particular, we answer (a) how electrons are accelerated to tens of keV in the magnetotail of Mercury, (b) how electrons move in the inner dipole-like region of the magnetosphere, and (c) how electrons interact with the exosphere and planetary surface. In the tail, we observe strong electron acceleration up to tens of keV as a consequence of magnetic reconnection, when the interplanetary magnetic field is directed southward. Such energetic electrons are trapped in adiabatic orbits in the dipolar magnetic field of the planet mainly at nightside. Accelerated electrons precipitate onto the surface mainly in the midnight-to-dawn sector (local time 0-6) as a consequence of curvature and grad-B drifts. Electron precipitation drives efficient ionization of multiple exospheric species (H, He, O, and Mn) and emission of X-rays from the surface of the planet in an aurora-like fashion. Our results unveil the nature of the high-energy electrons observed in the magnetotail of Mercury by past missions (Mariner10 and MESSENGER) and recently by the mission BepiColombo. High-energy electrons are injected from magnetic reconnection in the tail following a substorm-like process that strongly depends on the direction of the interplanetary magnetic field.

Fichier non déposé

Dates et versions

insu-04796049 , version 1 (21-11-2024)

Identifiants

Citer

Federico Lavorenti, Pierre Henri, Francesco Califano, Jan Deca, Simon Lindsay, et al.. Unveiling the electron kinetic physics at Mercury using global numerical simulations. AGU Fall Meeting 2023, Dec 2023, San Francisco, United States. ⟨insu-04796049⟩
109 Consultations
0 Téléchargements

Partager

  • More