Date of Award

Winter 2012

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

Benjamin G D Chandran

Abstract

Determining the mechanisms that heat the solar corona is a fundamental problem in heliospheric physics. One of the proposed models is based on low-frequency Alfven waves (o << O i) launched from the coronal base. Theoretical studies and numerical simulations have shown that Alfven-wave low-beta turbulence primarily cascades to smaller scales perpendicular to the mean magnetic field rather than smaller parallel scales, where beta = 8pip/B 2 is the ratio of the plasma pressure to the magnetic pressure. Because of this, the wave frequencies at small scales remain small compared to the proton cyclotron frequency. In this work, we study the possibility of ion heating by this low-frequency Alfven-wave turbulence in a reduced magnetohydrodynamic (RMHD) simulation. In a low-beta plasma, when an ion's gyroradius is comparable to the wave length in the perpendicular direction, the ion undergoes a random walk in the time-varying electrostatic potential. When the fluctuation amplitude exceeds a certain threshold, this stochastic mechanism provides ion heating in the plane perpendicular to the magnetic field lines. We evaluate the stochastic heating rate as a function of the amplitude of the turbulence and compare our findings to previous theoretical results.

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