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Home > Seminars and Workshops > Past seminars, PhD & HDR defense > 2010 > Séminaires 2010 > Le jeudi 2 décembre 2010 à 11 heures

Le jeudi 2 décembre 2010 à 11 heures

Pablo Garcia-Martinez - Dynamics of magnetic relaxation

Le jeudi 2 décembre 2010 à 11 heures à Palaiseau (salle de conférences du LIX)

Magnetic relaxation is a process observed in several laboratory and
astrophysical plasmas. It is triggered by some macroscopic
magnetohydrodynamic (MHD) instability whose non-linear evolution produces
a rapid redistribution of currents inside the plasma and strong magnetic
energy dissipation. Such evolution frequently settles the plasma into a
largely stable “quiescent” state (or relaxed state). In conventional
tokamaks, these events are (almost) always undesirable, because they
degrade the confinement. However, there are other devices, such as the
spheromak, the spherical tokamak or the reversed field pinch (RFP), which
rely on magnetic relaxation to initiate and/or sustain the plasma
configuration. In this talk, I will introduce recent studies on the
dynamics of the relaxation during the injection of magnetic helicity in
spheromaks. Firstly, I will briefly describe the fundamental assumptions
of the relaxation theory of J. B. Taylor [PRL 33, 1139 (1974)] and revise
the concepts of magnetic helicity and helicity injection current drive.
Secondly, the physical model (viscous-resistive-MHD) will be introduced
as well as the numerical approach employed (finite volume method).
Finally, the results of the numerical simulations will be interpreted and
compared with observations. The relationship with the relaxation of solar
coronal loops will be outlined.


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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