HR: 14:40h
AN: SM23D-05    [Abstracts]
TI: Mirror instability near the threshold: Hybrid simulations
AU: * Hellinger, P
EM: petr.hellinger@ufa.cas.cz
AF: Institute of Atmospheric Physics, AS CR, Bocni II/1401, Prague, 14131, Czech Republic
AU: Trávníček, P
EM: trav@ufa.cas.cz
AF: Institute of Atmospheric Physics, AS CR, Bocni II/1401, Prague, 14131, Czech Republic
AU: Passot, T
EM: Thierry.PASSOT@obs-nice.fr
AF: Observatoire de la Côte d'Azur, CNRS, B.P. 4229, Nice, 06304, France
AU: Sulem, P
EM: Pierre-Louis.Sulem@obs-nice.fr
AF: Observatoire de la Côte d'Azur, CNRS, B.P. 4229, Nice, 06304, France
AU: Kuznetsov, E A
EM: kuznetso@itp.ac.ru
AF: L.D. Landau Institute of Theoretical Physics, 2 Kosygin street, Moscow, 119334, Russian Federation
AU: Califano, F
EM: califano@df.unipi.it
AF: Dipartimento di Fisica, Università di Pisa, Largo Pontercorvo n.3, Pisa, 56127, Italy
AB: Nonlinear behavior of the mirror instability near the threshold is investigated using 1-D hybrid simulations. The simulations demonstrate the presence of an early phase where quasi-linear effects dominate [ Shapiro and Shevchenko, 1964]. The quasi-linear diffusion is however not the main saturation mechanism. A second phase is observed where the mirror mode is linearly stable (the stability is evaluated using the instantaneous ion distribution function) but where the instability nevertheless continues to develop, leading to nonlinear coherent structures in the form of magnetic humps. This regime is well modeled by a nonlinear equation for the magnetic field evolution, derived from a reductive perturbative expansion of the Vlasov-Maxwell equations [ Kuznetsov et al., 2007] with a phenomenological term which represents local variations of the ion Larmor radius. In contrast with previous models where saturation is due to the cooling of a population of trapped particles, the resulting equation correctly reproduces the development of magnetic humps from an initial noise. References
Kuznetsov, E., T. Passot and P. L. Sulem (2007), Dynamical model for nonlinear mirror modes near threshold, Phys. Rev. Lett., 98, 235003. Shapiro, V. D., and V. I. Shevchenko (1964), Sov. JETP, 18, 1109.
DE: 2728 Magnetosheath
DE: 2753 Numerical modeling
DE: 2772 Plasma waves and instabilities (2471)
DE: 7829 Kinetic waves and instabilities
DE: 7839 Nonlinear phenomena (4400, 6944)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting