Understanding the deflection of the `Cartwheel CME': data analysis and modeling

Abstract

We study the low corona evolution of the `Cartwheel' coronal mass ejection (CME; 2008-04-09) by reconstructing its 3D path and modeling it with magneto-hydrodynamic simulations. This event exhibits a double-deflection that has been reported and analyzed in previous works but whose underlying cause remained unclear. The `Cartwheel CME' travels toward a coronal hole (CH) and against the magnetic gradients. Using a high-cadence, full trajectory reconstruction, we accurately determine the location of the magnetic flux rope (MFR) and, consequently, the magnetic environment in which it is immersed. We find a pseudostreamer (PS) structure whose null point may be responsible for the complex evolution of the MFR at the initial phase. From the pre-eruptive magnetic field reconstruction, we estimate the dynamic forces acting on the MFR and provide a new physical insight on the motion exhibited by the 2008-04-09 event. By setting up a similar magnetic configuration in a 2.5D numerical simulation we are able to reproduce the observed behavior, confirming the importance of the PS null point. We find that the magnetic forces directed toward the null point cause the first deflection, directing the MFR towards the CH. Later, the magnetic pressure gradient of the CH produces the reversal motion of the MFR.