CORONAL MAGNETIC RECONNECTION DRIVEN BY CME EXPANSION—THE 2011 JUNE 7 EVENT

Abstract

Coronal mass ejections (CMEs) erupt and expand in a magnetically structured\nsolar corona. Various indirect observational pieces of evidence have shown that\nthe magnetic field of CMEs reconnects with surrounding magnetic fields,\nforming, e.g., dimming regions distant from the CME source regions. Analyzing\nSolar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on\n2011 June 7, we present the first direct evidence of coronal magnetic\nreconnection between the fields of two adjacent ARs during a CME. The\nobservations are presented jointly with a data-constrained numerical\nsimulation, demonstrating the formation/intensification of current sheets along\na hyperbolic flux tube (HFT) at the interface between the CME and the\nneighbouring AR 11227. Reconnection resulted in the formation of new magnetic\nconnections between the erupting magnetic structure from AR 11226 and the\nneighboring active region AR 11227 about 200 Mm from the eruption site. The\nonset of reconnection first becomes apparent in the SDO/AIA images when\nfilament plasma, originally contained within the erupting flux rope, is\nre-directed towards remote areas in AR 11227, tracing the change of large-scale\nmagnetic connectivity. The location of the coronal reconnection region becomes\nbright and directly observable at SDO/AIA wavelengths, owing to the presence of\ndown-flowing cool, dense (10^{10} cm^{-3}) filament plasma in its vicinity. The\nhigh-density plasma around the reconnection region is heated to coronal\ntemperatures, presumably by slow-mode shocks and Coulomb collisions. These\nresults provide the first direct observational evidence that CMEs reconnect\nwith surrounding magnetic structures, leading to a large-scale re-configuration\nof the coronal magnetic field.\n