Statistics – Computation
Scientific paper
Sep 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt........16m&link_type=abstract
Thesis (PHD). UNIVERSITY OF COLORADO AT BOULDER , Source DAI-B 59/03, p. 1155, Sep 1998, 476 pages.
Statistics
Computation
7
Scientific paper
Convection is of fundamental importance in the sun. It is primarily responsible for a large variety of observable phenomena, including differential rotation and the solar dynamo. Previous numerical simulations of global-scale solar convection in rotating spherical shells of fluid have been restricted by computational resources to deal with nearly laminar flow regimes. Disparities between the differential rotation profiles that such models predict and those deduced from helioseismology, coupled with recent advances in high performance computing, prompted my collaborators and to begin pursuing numerical simulations of global-scale convection turbulent parameter regimes. In order to take full advantage of available computational resources, we have developed a sophisticated numerical model specifically designed to run highly efficiently on massively parallel supercomputer architectures. Part I of this thesis includes a description of this model and the first scientific results it has produced. We have found that transport by nonlinear advection in the turbulent flow regime gives rise to a qualitatively different redistribution of angular momentum relative to laminar flows that more closely matches the inferred solar differential rotation. A number of other consequences of turbulence and its interaction with rotation have also been investigated, as well as the influence and nature of convective penetration into a stably-stratified interior. Part II of this thesis concerns several aspects of the fluid dynamical processes occurring in interstellar molecular clouds. Extensive mappings of carbon monoxide line emission in several densely sampled regions are analyzed in terms of the one- and two-point statistics of their velocity centroids, interpreted as quantitative descriptors of their underlying dynamics. Although some of the statistical properties are very suggestive of laboratory experiments and numerical simulations of turbulent flows, others remain enigmatic. The propagation of MHD shock waves in 'clumpy' interstellar clouds is also considered, using a simple one-dimensional analytic model. Particular emphasis is placed on how internal motions can be generated via direct shock acceleration and induced MHD wave fields. The former mechanism is found to be relatively more efficient.
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