HR: 1340h
AN: SM23B-0423    [Abstracts]
TI: On the propagation of low frequency MHD perturbations in thin current sheets: Theory and CLUSTER observations
AU: * Louarn, p
EM: philippe.louarn@cesr.fr
AF: CESR, Av. du colonel Roche, Toulouse, 31017 France
AU: Fruit, G
EM: fruit@math.waikato.ac.nz
AF: Depart. of mathematics, University of Waikato, Hamilton, 3105 New Zealand
AU: Tur, A
EM: anatoly.tour@cesr.fr
AF: CESR, Av. du colonel Roche, Toulouse, 31017 France
AU: Sauvaud, J
EM: jean-andre.sauvaud@cesr.fr
AF: CESR, Av. du colonel Roche, Toulouse, 31017 France
AU: Lucek, E
EM: e.lucek@imperial.ac.uk
AF: The Blackett lab., Imperial College, London, SW7 2BZ United Kingdom
AB: This study is a contribution to the analysis of the 'turbulence' observed in the plasmasheet. Given that linear perturbations could be a constituant of the actual fluctuations, we use Harris and modified Harris (with a non nul Bz component) models to determine the low frequency perturbations that may propagate in thin current sheets.This analysis thus extends the previous studies performed in a 1D Harris sheet (Fruit et al 2002 and 2004)which already showed a good agreement with the observations performed during some time periods. The goal is to capture the main characteristics of the MHD perturbations (a mixture of alfvenic and magnetosonic fluctuations given the non-homogeneity of the structure) in a more complex 2D model in order to estimate their importance in the constitution of the observed magnetic 'turbulence'. From plasma and magnetic measurements of the 4 Cluster spacecraft, we estimate the general parameters of the current sheet (orientation, thickness, sound and Alfven speed), we deduce what would be general characteristics of the linear MHD fluctuations in this non-homogeneous structure and compare them with the observed 'turbulence'. We show that, in some circumstances, the 'turbulence' could correspond to such linear MHD perturbations that have reached large amplitudes. Not surprisingly, this is not the most general case and kinetic or non-MHD effects as well as non linear effects certainly play a fundamental role.
DE: 2744 Magnetotail
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2764 Plasma sheet
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005