Flux Tube Dynamics in the Presence of Mass Flows

Abstract

Mass flows observed throughout the solar atmosphere exhibit many patterns. They are observed in a wide temperature range of $3 \times 10^4$–$10^7$ K, and can have a steady, unsteady, or explosive character. Their amplitudes vary from a few tenths of km s$^{-1}$ at the photosphere up to hundreds of km s$^{-1}$ in the transition region and corona. The presence of mass flows drastically changes the dynamics of magnetic structures, and most importantly, plays a crucial role in the processes of the energy production, transfer, and release. Depending on the geometry and intensity of the flow, the system of magnetic flux tubes exhibits a number of unusual phenomena that are directly observed. In this chapter, we consider mainly two effects associated with the presence of mass flows. One is the instability of negative-energy waves (NEWs) and other lies in the range of velocities beyond the instability threshold, namely the effect of mass flows on the energy transfer by the phase mixed Alfvén waves.