Structure of small-scale magnetic flux tubes and excitation of sausage mode oscillations

Abstract

The nature of small-scale magnetic fields in the solar atmosphere is discussed. In the first part of the review, equilibrium models for the structure of magnetic flux tubes are presented. It is shown that the thermodynamic properties of the flux tube atmosphere are sensitive to energy transport by radiation. A comparison of the results with observations shows that the temperature and magnetic field strength are in broad agreement. In the second part, the linear interaction of a flux tube with sound waves or p-modes in the external medium is analysed. The idealized case of an isothermal atmosphere is considered, which allows the mathematical problem to be solved exactly. The detailed behaviour of the flux tube response and its dependence on various parameters is analysed. It is pointed out that in general the interaction is non-resonant. An application of the results to the solar atmosphere is discussed.