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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2010 > Séminaires 2010 > Le jeudi 16 septembre à 14h

Le jeudi 16 septembre à 14h

Patrick Diamond
(Professor of Physics at the "University of California San Diego,
Department of Physics" and "the Center for Astrophysics and Space
Sciences (CASS)". He is also the director of the Korean "WCI Center
for Fusion Plasma Theory, NFRI".)

Mixing, Memory and Magnetism : PV Dynamics and Zonal Flow Formation in Drift Wave Turbulence and Beta Plane MHD

Jeudi 16 sept 2010 14h Salle de conférence du LIX, Palaiseau

Zonal flows are ubiquitous in laboratory plasmas and geophysical
fluids,and are an important player in the process of momentum
transport and turbulence self-regulation.Here,we take a "second look"
at zonal flows from the point of view of real space dynamics of
potential vorticity (PV) and momentum/pseudomomentum conservation
theorems.This approach is complementary to the usual MFE community
perspective derived from inverse cascade and/or modulational
instability. Specifically,we examine the mechanisms of PV mixing and
memory decay in drift wave turbulence,in the context of both fluid and
kinetic models,and use the insights gleaned to construct
pseudomomentum conservation theorems analogous to to the
Charney-Drazin theorem, familiar from GFD.These pseudomomentum theorems
reveal a great deal about the spatial structure and drive dynamics of
plasma zonal flows WITHOUT the need for a Reynolds stress closure,and
so are a useful complement to standard approaches.Several insights into
the structure of drift wave -zonal flow turbulence are presented and
discussed.We then consider weakly magnetized beta plane MHD.In that
case,we show that even a weak magnetic field is sufficient to inhibit
PV mixing on account of the freezing-in law .This results in quenching
of zonal flow formation.We argue that this quench is intrinsically
magnetic Reynolds number dependent,as is its closely related 2D
counterpart,the quench of turbulent resistivity .We conclude with a
brief discussion of the implications for momentum transport in the
solar tachocline.


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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)