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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2010 > Séminaires 2010 > Le mardi 9 novembre 2010 à 11 heures

Le mardi 9 novembre 2010 à 11 heures

Fouad Sahraoui

Le mardi 9 novembre 2010 à 11 heures à Palaiseau (amphi Pierre Curie)

Kinetic cascade and dissipation of solar wind turbulence : Cluster observations and theoretical modeling

Large scale solar wind (SW) turbulence, where the MHD approximation is valid, has been extensively studied over the past decades, both observationally and theoretically. A general consensus exists that turbulence at those scales is dominated by strongly nonlinear Alfvén waves, yielding power law spectra with the Kolmogorov scaling k-5/3. In contrast, sub-proton or electron scales SW turbulence have been only recently explored by using data from the four Cluster satellites [Sahraoui et al., 2009, 2010c ; Alexandrova et al., Kiyani et al., 2009]. Despite this significant progress, a strong debate continues as to the actual nature of the turbulence in this region of the spectrum, i.e., whether or not it is kinetic Alfvén waves (KAW) or whistler turbulence. This is a key question that relates directly to the problem of plasma heating and particle acceleration in space or astrophysics. Here we review recent results on SW turbulence obtained thanks to the high time resolution and multipoint Cluster data. We show the importance of the kinetic effects occurring at the sub-proton scales that may explain the problem of plasma heating in the SW. We also show recent theoretical results (based on the linear Vlasov theory) that may help resolving the controversy on the actual nature (whistler or KAW) of the sub-proton scale turbulence.


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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Hébergeur : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
Directeur de la publication : Pascal Chabert (Directeur)