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Tim Duckenfield (CFSA, Warwick): Slow mode waves in a finite-beta plasma: the effects of heating/cooling misbalance

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Abstract: Slow magnetoacoustic waves are a common feature of many plasma systems, and the study of their dispersion properties allows one to probe the local plasma conditions which otherwise may be difficult to measure. Often these plasma systems are maintained at thermal equilibrium by a delicate balance between continuous heating and cooling mechanisms. As a slow wave propagates through the plasma, the wave perturbs both the plasma's mechanical and thermal equilibrium. Thus if the plasma is continuously being heated and cooled at thermal equilibrium, the wave induces a misbalance between these competing processes. This wave-induced misbalance causes dispersion and amplification/damping of the slow wave, due to the presence of a characteristic time scale(s) in the system: how quickly the perturbation returns to, or destroys, the equilibrium.

In this seminar I will describe some of the important effects that arise from the heating/cooling misbalance, such as the damping or amplification of the wave. In particular I will extend the zero-beta dispersion relation to account for a finite-beta plasma. Finally I want to demonstrate how we may use these slow waves as probes in the solar corona, to help answer one of the biggest physics mysteries in plasma physics: how is the corona still hot?!

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