HR: 1340h
AN: NG23A-1185    [Abstracts]
TI: Density and Temperature Spectra in the Solar Wind: Nearly Incompressible Modelling
AU: * Shaikh, D
EM: dastgeer@ucr.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521 United States
AU: Zank, G P
EM: zank@ucr.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521 United States
AB: Density and temperature spectra in the solar wind frequently exhibit a Kolmogorov-like spectrum. Remarkably, interstellar scintillation and angular radio wave broadening measurements also show that interstellar (electron) density fluctuations exhibit a Kolmogorov-like $k^{-5/3}$ power spectrum extending over many decades in wavenumber space. The ubiquity of the Kolmogorov-like interplanetary and interstellar medium (ISM) density spectrum led to an explanation based on the coupling of incompressible magnetohydrodynamic (MHD) fluctuations to density fluctuations through a ``pseudosound'' relation within the context of ``nearly incompressible'' (NI) hydrodynamics (HD) and MHD models. The NI theory provides a fundamentally different explanation for the observed ISM density spectrum in that density fluctuations can be a consequence of passive scalar convection due to background incompressible fluctuations. Depending upon the amplitude of thermal, pressure and density fluctuations, there exist two distinct approaches to incompressibility. When density and temperature dominate the pressure fluctuations, the NI regime is called heat fluctuation dominated (HFD). On the other hand, when all the fluctuations are comparable heat fluctuation modified (HFM) NI regime results. Here, we present results of our two dimensional nonlinear fluid simulations, exploring various nonlinear aspects, that lead to inertial range ISM turbulence within the context of the NI hydrodymanics models. In qualitative agreement with the NI predictions and in-situ observations, we find that the density fluctuations exhibit a Kolmogorov-like spectrum via a passive convection in the field of the background incompressible fluctuations in both the regimes.
DE: 2144 Interstellar gas
DE: 2159 Plasma waves and turbulence
DE: 2164 Solar wind plasma
DE: 2467 Plasma temperature and density
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting