Dissertation/Thesis Abstract

Magnetogenesis through Relativistic Velocity Shear
by Miller, Evan, Ph.D., Dartmouth College, 2016, 95; 10001975
Abstract (Summary)

Magnetic fields at all scales are prevalent in our universe. However, current cosmological models predict that initially the universe was bereft of large-scale fields. Standard magnetohydrodynamics (MHD) does not permit magnetogenesis; in the MHD Faraday’s law, the change in magnetic field B depends on B itself. Thus if B is initially zero, it will remain zero for all time. A more accurate physical model is needed to explain the origins of the galactic-scale magnetic fields observed today. In this thesis, I explore two velocity-driven mechanisms for magnetogenesis in 2-fluid plasma. The first is a novel kinematic ‘battery’ arising from convection of vorticity. A coupling between thermal and plasma oscillations, this non-relativistic mechanism can operate in flows that are incompressible, quasi-neutral and barotropic. The second mechanism results from inclusion of thermal effects in relativistic shear flow instabilities. In such flows, parallel perturbations are ubiquitously unstable at small scales, with growth rates of order with the plasma frequency over a defined range of parameter-space. Of these two processes, instabilities seem far more likely to account for galactic magnetic fields. Stable kinematic effects will, at best, be comparable to an ideal Biermann battery, which is suspected to be orders of magnitude too weak to produce the observed galactic fields. On the other hand, instabilities grow until saturation is reached, a topic that has yet to be explored in detail on cosmological scales. In addition to investigating these magnetogenesis sources, I derive a general dispersion relation for three dimensional, warm, two species plasma with discontinuous shear flow. The mathematics of relativistic plasma, sheared-flow instability and the Biermann battery are also discussed.

Indexing (document details)
Advisor: Rogers, Barrett
Commitee: Caldwell, Robert, Mahajan, Swadesh, Millan, Robyn
School: Dartmouth College
Department: Physics and Astronomy
School Location: United States -- New Hampshire
Source: DAI-B 77/06(E), Dissertation Abstracts International
Subjects: Physics, Plasma physics
Keywords: Kelvin-helmholtz, Magnetogenesis, Plasma, Relativsitic
Publication Number: 10001975
ISBN: 9781339417042
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