The Evolution of Galactic and Intergalactic Magnetic Fields

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AST-0507367ZweibelThis project will help to clarify one of the fundamental questions of astrophysics: what is the origin of magnetic fields, and how do they evolve? Observations show that magnetic fields existed in galaxies and in the intergalactic medium by the time the Universe was less than a tenth its present age. It seems unlikely these fields were created in the Big Bang, and recent work suggests they arose by the creation of a small 'seed' field and its subsequent amplification by hydro-magnetic turbulence. This idea still faces significant technical difficulties. This research will consider the interaction of energetic particles, or cosmic rays, with very weak magnetic fields, exploring the exchange of energy both analytically and numerically. It will investigate a conjectured 'bootstrap' process whereby streaming cosmic rays amplify helical fluctuations, growing the magnetic field and accelerating cosmic rays, which amplify more fluctuations, and so on. This study should also lead to an improved theory for cosmic ray acceleration in the intergalactic medium, including testable predictions based on radiative and nucleosynthetic signatures.The research will train at least one student in advanced computing and in interdisciplinary work at the interface between astrophysics and plasma physics.