Computer Science – Numerical Analysis
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........11v&link_type=abstract
PhD Dissertation, Maryland Univ. College Park, MD United States
Computer Science
Numerical Analysis
5
Magnetohydrodynamic Turbulence, Solar Wind, Turbulence Models, Plasma Heating, Energy Spectra, Plasma Temperature, Energy Dissipation, Magnetohydrodynamic Flow, Kolmogorov Theory, Wentzel-Kramer-Brillouin Method, Magnetic Fields, Flux Density, Numerical Analysis, Homogeneous Turbulence, Solar Wind Velocity
Scientific paper
In this thesis we apply MHD turbulence phenomenologies, namely the Kolmogorov-like and Kraichnan's phenomenologies, to the evolution of amplitude, cross helicity, and temperature in the solar wind. Using an energy equation and assuming that the solar wind is a locally homogeneous incompressible 'dissipationless' turbulent magnetofluid, we show that the amplitude evolution of the solar wind fluctuations is close to the WKB predictions, which is consistent with the solar wind observations. We find that 'dynamic alignment' (increase in normalized cross helicity sigma(c)) can occur in the Kolmogorov-like phenomenology; however, if the large-scale 'inward' and 'outward' propagating Alfvenic fluctuations are approximately equal and the small-scale fluctuations obey the Kolmogorov-like phenomenology, sigma(c) decreases with time, a result consistent with the solar wind observations. We have estimate the amount of turbulent dissipation and temperature evolution in the solar wind using the MHD turbulence models, the emphasis being on the Kolmogorov-like model. We find that no existing turbulence phenomenology can consistently explain the observed T(r), but enough energy flux is available for turbulent heating to be a likely contributor to the heating of the solar wind. We also perform numerical simulations of MHD turbulence and compare the numerical results with the model predictions and with the solar wind observations. The ratio of the largest inertial range fluctuation amplitude to the mean magnetic field for the numerical simulations is comparable to the corresponding ratio in the solar wind. In the numerical simulations it is difficult to distinguish between the power-law indices of 5/3 (Kolmogorov-like) and 3/2 (Kraichnan) for the energy spectra, but a power law spectrum is established. However, the analysis of energy cascade rates show that for small sigma(c), the numerical results are generally consistent with the predictions of the Kolmogorov-like model. Hence, for small sigma(c) our numerical simulations appear to be consistent with the observed k-5/3 energy spectra in the solar wind. The numerical results and the temperature evolution of Alfvenic streams differ significantly from those of non-Alfvenic streams, which suggests that turbulence models depend on normalized cross helicity sigma(c) in a more complex fashion than present in the existing phenomenologies.
No associations
LandOfFree
Magnetohydrodynamic turbulence models of solar wind evolution does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Magnetohydrodynamic turbulence models of solar wind evolution, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetohydrodynamic turbulence models of solar wind evolution will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1684844