Magnetosonic Streaming

Abstract

The Faraday effect in gas dynamics called acoustic streaming and its accompanying nonlinear phenomena is found to have analogies in plasma magnetohydrodynamics. A natural place where these effects occur is the solar atmosphere covered by random ensembles of magnetic flux tubes. Unlike acoustic streaming, magnetosonic streaming consisting of the generation of plasma flows by an oscillating flux tube, is accompanied by a current drive and results in a specific evolution of magnetic structures. Depending on the physical parameters of a system, a single magnetic flux tube may be either split into thinner flux tubes or be diffusively dissolved into the ambient plasma. The effect of the magnetosonic streaming on one hand, is an obvious candidate for the generation of electric currents and mass flows at magnetic flux tube sites, and, on the other hand, it determines the evolution of magnetic structures, like, e.g., their fragmentation processes, and ultimately their lifetimes. In this chapter, we shall describe the nature and origin of the magnetosonic streaming and then use the theory to explain observed regularities in the evolution of photospheric flux tubes. Some regimes will be also verified in numerical simulation. Application of these results to observed properties of photospheric flux tubes will be given both in the qualitative and quantitative analysis.