The magnetohydrodynamical Kelvin-Helmholtz instability and the investigation for coronal mass ejections

Main aim of this thesis study is to investigate the definition and the formation mechanism of Kelvin-Helmholtz instability occured in the fluid when the shear velocity exists at the density interfaces. Secondly, to study the processes at the density interfaces in plasma defined as a magnetised fluid and to search the effects of fundamental parameters like magnetic field, shear velocity and wave number on the growth rate of the instability. While the increasing values of magnetic field are removing the instability, the higher values of shear velocity have an enhancing effect on the growth rate of instability. When the perturbations do not move along the shear velocity, it becomes easy to stabilize the instability. Additionally, it is also observed that the increasing values of wave number speed up the processes of stabilization and destabilization.As an application The Kelvin-Helmholtz instability possibly occured in Coronal Mass Ejections which is one of interesting subjects of Solar Physics was studied. In this investigation, occurrence and unoccurrence of instability are determined for the different values of magnetic field, shear velocity and wave number.Anahtar Kelimeler : Interface Instability, Kelvin-Helmholtz Instability, Magnetohydrodynamics, Shear Velocity, Magnetic Field, Sun, Coronal Mass Ejections.