A study of particle acceleration in the auroral regions of planetary magnetospheres

• Main Author: Génot, Vincent
• Other Authors: Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), Université de Versailles-Saint Quentin en Yvelines, Le Quéau Dominique
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 1999
• Subjects: auroral regions; Alfvén waves; non homogeneous plasma; energy dissipation; numerical simulations; régions aurorales; ondes d'Alfvén; plasma non homogène; accélération; dissipation d'énergie; simulations numériques; [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; aurores boréales
• Online Access: https://theses.hal.science/tel-00010474; https://theses.hal.science/tel-00010474/document; https://theses.hal.science/tel-00010474/file/tel-00010474.pdf

Particle acceleration is a topic of general astrophysical interest which can be studied in a convenient natural laboratory: the Earth's magnetosphere and, more widely, the magnetospheres of magnetised planets. In particular, numerous physical processes occur in the auroral regions, for example the northern and southern auroras, which are very spectacular but rather imperfectly understood phenomena. Numerous satellite measurements have shown the existence of highly energetic populations of particles flowing towards the Earth, and this implies the existence of a strong electric potential difference which most of the proposed models fail to predict. Generally speaking, an understanding of this acceleration is necessary to explain the dynamic coupling between the magnetosphere, where the energy is released during substorms, and ionosphere where the energy is dissipated. The study of the dissipation, which takes place on short spatial and temporal scales, constitutes the main theme of the present work. We consider as electromagnetic perturbation an Alfvén wave propagating along the geomagnetic field lines. Its interaction, in the auroral zones, with the highly inhomogeneous structures known as plasma cavities, leads to the formation of parallel electric fields able to accelerate particles, as well as to a significant energy transfer from the waves to the electrons. Finally, this study enables us to suggest a new scenario for the formation of auroral arcs. This work was conducted both analytically and numerically using a "particles in cell" code. L'accélération de particules est une thématique d'astrophysique générale qui peut être étudiée dans un laboratoire naturel : les régions aurorales de la Terre, et plus globalement, celles des planètes magnétisées. Ces régions sont en effet le siège de nombreux processus qui donnent, entre autres, naissance aux aurores boréales et australes, phénomènes spectaculaires mais dont de nombreux aspects restent incompris. En particulier, de multiples mesures de satellites ont ...