Dr. Devika Tharakkal

We study the evolution and saturation of the fully nonlinear Parker and magnetic buoyancy instabilities using three dimensional magnetohydrodynamical simulations of the interstellar medium in a Cartesian box. In order to simulate the nonlinear, statistically steady-state of the system, we impose background horizontal magnetic field, gas density and cosmic ray distributions as functions of height symmetric about the midplane. The nonlinear development of the Parker instability leads to a decrease in the gas scale height, accompanied by the evolution of the magnetic field towards a nearly uniform vertical distribution and vigorous spread of the cosmic rays through the system guided by the localized vertical magnetic fields. We also consider the effect of rotation on the evolution and saturation of the Parker instability. Rotation introduces dynamo effects in the system, which affect the dynamics of magnetic fields and cosmic rays. In particular, rotation results in a reversal of the imposed horizontal magnetic field, resulting in a vertical variation in the sign of the horizontal magnetic field direction. The qualitative evolution of cosmic rays and thermal gas is similar in both rotating and non-rotating cases, but the loss and saturation levels of magnetic field and cosmic rays differ quantitatively