APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011;
Anaheim, California
Session R4: So Many Dynamos: Flow Generated Magnetic Fields in Nature, in the Computer, and in the Lab II
1:30 PM–3:18 PM,
Monday, May 2, 2011
Room: Garden 4
Sponsoring
Units:
DPP DCOMP
Chair: Cary Forest, University of Wisconsin-Madison
Abstract ID: BAPS.2011.APR.R4.2
Abstract: R4.00002 : Magnetogenesis and magnetothermal equilibria in turbulent galaxy-cluster plasmas
2:06 PM–2:42 PM
Preview Abstract
Abstract
Author:
Alexander Schekochihin
(University of Oxford)
We do not know the exact mechanism of magnetic field generation in magnetised
weakly collisional (or collisionless) turbulent plasma. We do know that large-scale
MHD
motions in such plasmas are subject to fast small-scale kinetic instabilities (mirror
and
firehose) triggered (at high beta) by pressure anisotropies and that these
anisotropies
will always arise in a turbulent plasma. Therefore, standard MHD equations cannot
be
used to describe the turbulent dynamo. I will argue that the likely scenario in such
plasmas is explosively fast growth of magnetic fluctuations to dynamical levels. I will
further argue that if an efficient turbulent dynamo is assumed, radiative cooling in
such
plasmas can be balanced in a thermally stable way by turbulent heating, whose rate
is
set by the condition that plasma locally remains in a marginal state with respect to
the
mirror and firehose instabilities. This thermal stability suggests that a cooling
catastrophe is not inevitable, although whether this old problem is thus resolved
depends on whether a number of assumptions about the nonlinear behaviour of the
instabilities, strength of turbulence and efficiency of the dynamo are borne out by
first-
principles microphysical theory, simulations or plasma experiments.\\
References:\\
A. A. Schekochihin, M. Brueggen, L. Feretti, M. W. Kunz, and L. Rudnick,
Space Sci. Rev., in preparation (2011)\\
M. W. Kunz, A. A. Schekochihin, S. C. Cowley, J. J. Binney, and J. S. Sanders,
Mon. Not. R. Astron. Soc., in press (2011) [e-print arXiv:1003.2719]\\
M. S. Rosin, A. A. Schekochihin, F. Rincon, and S. C. Cowley,
Mon. Not. R. Astron. Soc., in press (2011) [e-print arXiv:1002.4017]\\
A. A. Schekochihin, S. C. Cowley, F. Rincon, and M. S. Rosin,
Mon. Not. R. Astron. Soc. 405, 291 (2010) [e-print arXiv:0912.1359]\\
A. A. Schekochihin, S. C. Cowley, R. M. Kulsrud, M. S. Rosin, and T. Heinemann,
Phys. Rev. Lett. 100, 081301 (2008) [e-print arXiv:0709.3828]\\
A. A. Schekochihin and S. C. Cowley,
Phys. Plasmas 13, 056501 (2006) [e-print astro-ph/0601246]\\
A. A. Schekochihin, S. C. Cowley, R. M. Kulsrud, G. W. Hammett, and P. Sharma,
Astrophys. J. 629, 139 (2005) [e-print astro-ph/0501362]
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.APR.R4.2