Magnetic reconnection at the dayside magnetopause in global Lyon-Fedder-Mobarry simulations

We find the simulations exhibit two qualitatively different reconnection processes. The first process we identify as three-dimensional topology merging along a separator line, in which solar wind and dipolar field lines reconnect, creating field lines with one foot point on the Earth and the other in the solar wind. For IMF angles of 45 and 90 degrees this topology merging is a predominantly antiparallel reconnection process concentrated near nulls in the magnetic cusps, while for larger IMF clock angles of 135 or 180 degrees the reconnection extends across belt-like regions spanning the subsolar point.

For clock angles of 45 and 90 degrees we also identify a second type of reconnection process that is a three-dimensional form of guide field reconnection and typically occurs in regions along the separator line closer to the subsolar point. This process can mediate the reconnection of solar wind field lines with each other or can couple to the topology merging, leading to a subset of field lines that exhibit reconnection in multiple locations at the same moment of time.