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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2013 > Séminaires 2013 > Le jeudi 24 octobre à 14h

Le jeudi 24 octobre à 14h

Khurom Kiyani - Using the Interplanetary Solar Wind to Investigate Plasma Turbulence

Lieu  : Palaiseau, salle de réunion de l’aile 0 (ex LIX)

Résumé  : Turbulence is not only the rule in most terrestrial flows that we experience, it is also ubiquitous in space and astrophysical plasmas. The problem of turbulence is not a problem of necessarily solving the equations of motion (many of us have given up on this) — the problem is instead to understand the various facets of the phenomenon. Collisionless plasmas introduce several layers of complexity that are not present in neutral hydrodynamics. These include, but are not limited to, the presence of anisotropy and plasma waves, and the lack of any appreciable viscous and resistive effects to noticeably dissipate the motion or allow mixing/diffusion of magnetic field lines. These and others, make the study of plasma turbulence a rich and actively investigated area in physics. My contention, and also shared by many in the community, is that turbulence not only has a noticeable effect on the plasma dynamics, it can vastly change the dynamics and dominate it — it is arguably the primary mechanism of multi-scale coupling in fast flowing plasmas. The presence of highly stochastic fields caused by turbulent dynamics, brings into question how one defines a background magnetic field ; how turbulence enhances the mixing of field lines ; and how turbulence and reconnection feedback into each other. The seminar will discuss some of these aspects and show how in-situ spacecraft observations of the solar wind, arguably the only in-situ accessible highly turbulent plasma, help to illuminate many aspects of plasma turbulence discussed above. In particular, I will be presenting results from a recent investigation [Kiyani et al., ApJ 2013] which uses the search-coil on the STAFF instrument from the Cluster mission to investigate anisotropy, scaling and the role of compressible fluctuations in turbulence at sub-ion Larmor scales.

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