HR: 1400h
AN: SM53A-06    [Abstracts]
TI: Kappa Velocity Distribution Results from Modeling Thermal Fluctuations in a Turbulent Plasma-sheet
AU: * Presicci, M
EM: presicci@colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80309-0392, United States
AU: Baker, D N
EM: Dan.Baker@lasp.colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80309-0392, United States
AB: Kappa velocity distributions are common to laboratory and space plasmas, and exhibit long power law (suprathermal) tails in comparison to Maxwell-Boltzmann distributions. Various processes, including spontaneous scattering by Langmuir and ion-sound waves, charge fluctuations, polydispersity in diffusing particle or random media sizes, induced scattering by photons, and other processes may generate kappa velocity distributions. Since electron and ion velocity measurements in the plasma sheet suggest a highly turbulent state, we consider whether thermal fluctuations in MHD turbulence are sufficient to generate kappa velocity distributions. We model the thermal fluctuations by Langevins equation with a white noise driver. The noise variance is set proportional to the expectation of the square of the local Kolmogorov speed in the turbulent plasma. The modeled variance fluctuates at times sampled from an exponential distribution representing independent increments in mean waiting interval between times of particle interaction with the turbulent plasma. The histogram for the resulting velocity distribution is plotted at pre-selected times, demonstrating the evolution from a chosen initial distribution to the kappa distribution.
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
DE: 2772 Plasma waves and instabilities (2471)
DE: 7853 Spacecraft/atmosphere interactions
DE: 7857 Stochastic phenomena (3235, 3265, 4475)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly