Surface and Fundamental Modes of Oscillations in Thin Coronal Loops

Abstract

The oscillations in thin magnetic flux tubes in the solar corona are considered. The surface and fundamental modes of oscillations are shown to be the main modes of fast and slow oscillations. The slow surface and fundamental modes are waveguide ones. The fast surface mode is a leaky one, while the fast fundamental mode is a waveguide one. The fundamental modes considered by us exist only in magnetic flux tubes affected by the environment. Our definition of the fundamental modes does not coincide with the universally accepted one. Present-day observations of oscillations in coronal loops can hardly record the slow sausage modes, the first of which is considered as the fundamental one. The fast sausage modes should not be observed at a poor spatial resolution either. The first fast sausage mode, which is commonly considered as the fundamental one, is an exception. However, this mode is absent in thin magnetic flux tubes.