Cosmic Ray Hydrodynamics

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AST-0907837ZweibelInterstellar and intergalactic gas is pervaded by relativistic charged particles known as cosmic rays, which account for a significant fraction of the energy density in the gas. A fluid theory of cosmic rays has been developed in which collisions with tiny electromagnetic fluctuations mimic collisions with particles, capturing cosmic ray physics on large scales and allowing some beautiful simulations of galaxy clusters and large scale structure formation. This project will extend and generalize the fluid picture of cosmic rays so as to capture viscous effects and to treat cosmic ray interaction with very weak magnetic fields in the intergalactic medium and in galaxies and galaxy clusters at early times. This improved picture will then be applied to assess the thermal stability and overall viscosity of intracluster gas, to estimate the rate at which intergalactic plasma is heated by cosmic rays, and to study the effects of cosmic rays on the stability of hot X-ray cavities in clusters. This work develops microscale physics through analytic calculation and state-of-the-art numerical simulations of restricted scope. The small scale processes that will be studied also apply to interstellar environments, to pulsar wind nebulae, and even to laboratory plasmas.The research will help to build bridges between the plasma physics and high energy neutrino astrophysics groups at the University of Wisconsin. The work involves postdoctoral training, undergraduate research, and public outreach using existing facilities and programs.This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).