A simulation of a CME propagation and shock evolution in the lower solar corona

We present a simulation of the evolution of a CME (~800km/s at 5 solar radii) in the lower solar corona (until 5 solar radii) using Space Weather Modeling Framework (SWMF). The configuration of the sun's magnetic field is based on the MDI data on the solar surface during Carrington Rotation 1922. The pre-CME background solar wind is generated under this boundary condition and Wang-Sheeley-Arge (WSA) model. To initiate a CME, we inserted a Titov-Demoulin flux rope in an active region near the solar equator. The zone along nose of the CME is refined to resolve the CME-driven-shock. Our results show that a higher density region is followed by a dark cavity behind the shock and the higher density region is expanding while propagating away from the sun. These features are consistent with the CME observations which shows that a bright front followed by a dark area after the shock. After the initiation stage, in which the CME has a large acceleration followed by a deceleration, the CME demonstrates a nearly constant and slow acceleration of the order of 100m/s 2. At 5 solar radii, the CME has a speed of 800km/s. Although CME is accelerating, the Mach number of the shock is decreasing because the Alfven speed upstream of the shock is increasing. Detailed analysis of the pressures on the CME shows that the thermal pressure account for most of the acceleration of the CME and the magnetic pressure contribute to the acceleration at an early time but it becomes negligible when the CME moves further away from the sun. We also present the evolution of shock geometry near the nose of the CME and find that the shock is nearly perpendicular. Further investigation of the dependency in latitude of the shock and their effects on particle acceleration are required in a future work.