3D numerical experiment for EUV waves caused by flux rope eruption

Abstract

ABSTRACT We present a 3D magnetohydrodynamic numerical experiment of an eruptive magnetic flux rope (MFR) and the various types of disturbances it creates, and employ forward modelling of extreme ultraviolet (EUV) observables to directly compare numerical results and observations. In the beginning, the MFR erupts and a fast shock appears as an expanding 3D dome. Under the MFR, a current sheet grows, in which magnetic field lines reconnect to form closed field lines, which become the outermost part of an expanding coronal mass ejection (CME) bubble. In our synthetic SDO/AIA images, we can observe the bright fast shock dome and the hot MFR in the early stages. Between the MFR and the fast shock, a dimming region appears. Later, the MFR expands so its brightness decays and it becomes difficult to identify the boundary of the CME bubble and distinguish it from the bright MFR in synthetic images. Our synthetic images for EUV disturbances observed at the limb support the bimodality interpretation for coronal disturbances. However, images for disturbances propagating on-disc do not support this interpretation because the morphology of the bright MFR does not lead to circular features in the EUV disturbances. At the flanks of the CME bubble, slow shocks, velocity vortices and shock echoes can also be recognized in the velocity distribution. The slow shocks at the flanks of the bubble are associated with a 3D velocity separatrix. These features are found in our high-resolution simulation, but may be hard to observe as shown in the synthetic images.