A statistical study of the propagation characteristics of whistler waves observed by Cluster

Autor: Agapitov, Oleksiy, Krasnoselskikh, Vladimir, Khotyaintsev, Yuri V., Rolland, Guy
Přispěvatelé: Department of Astronomy and Space Physics [Kyiv], Taras Shevchenko National University of Kyiv, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Swedish Institute of Space Physics [Kiruna] (IRF), Centre National d'Études Spatiales [Toulouse] (CNES), CNES through the grant 'Modeles d’ondes', and by the ECO NET program of the EGIDE (France)Swedish Research Council, grant 2007‐4377
Jazyk: angličtina
Rok vydání: 2011
Předmět:
Zdroj: Geophysical Research Letters
Geophysical Research Letters, American Geophysical Union, 2011, 38, L20103 (6 p.). ⟨10.1029/2011GL049597⟩
ISSN: 0094-8276
1944-8007
Popis: International audience; [1] VLF waves play a crucial role in the dynamics of radiation belts, and are responsible for the loss and the acceleration of energetic electrons. Modeling wave‐particle interactions requires the best possible knowledge for how wave energy and wave‐normal directions are distributed in L‐shells and for the magnetic latitudes of different magnetic activity conditions. In this work, we performed a statistical study for VLF emissions using a whistler frequency range for nine years (2001–2009) of Cluster measurements. We utilized data from the STAFF‐SA experiment, which spans the frequency range from 8.8 Hz to 3.56 kHz. We show that the wave energy distribution has two maxima around L ∼ 4.5 − 6 and L ∼ 2, and that wave‐normals are directed approximately along the magnetic field in the vicinity of the geomagnetic equator. The distribution changes with magnetic latitude, and so that at latitudes of ∼30°, wave‐normals become nearly perpendicular to the magnetic field. The observed angular distribution is significantly different from Gaussian and the width of the distribution increases with latitude. Since the resonance condition for wave‐particle interactions depends on the wave normal orientation, our results indicate that, due to the observed change in the wave‐normal direction with latitude, the most efficient particle diffusion due to wave‐particle interaction should occur in a limited region surrounding the geomagnetic equator.
Databáze: OpenAIRE
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