Conditions For Wave Propagation Along Solar Magnetic Flux Tubes

Abstract

There is an intimate relation between all aspects of the solar activity and the presence of solar magnetic fields. Observations showed that the magnetic field at the photospheric level consists of magnetic flux tubes, which are located at supergranule boundaries. The flux tubes interact with the solar granulation and convection and, as a result, longitudinal, transverse and torsional magnetic tube waves are generated. These waves are responsible for carrying the energy to the upper parts of the solar atmosphere and heating the atmosphere to temperatures much higher than the solar photosphere. The energy carried by transverse and torsional waves may also play a dominant role in acceleration of the solar wind. It is important to determine the propagation conditions for all three types of magnetic tube waves. The main purpose of analytical studies performed in this thesis is to derive cutoff frequencies for the waves propagating along thin and vertically oriented magnetic flux tubes, and to determine the range of frequencies corresponding to propagating and evanescent waves under the solar conditions. Among new results obtained in this thesis is an alternative much simpler approach to derive the transverse wave equation, the derivation of the wave equation for torsional waves propagating along different parts of exponentially diverging flux tubes, and the cutoff frequencies for torsional waves.