Speaker
Description
The Earth’s magnetotail is formed primarily of magnetic field lines that are topologically open, i.e. connected to the interplanetary magnetic field (IMF). During periods of northward-directed IMF, the magnetopause reconnection site moves tailward of the cusps, resulting in either the ‘stirring’ of magnetic flux without a net change in topology (“single lobe reconnection”), or the closure of the open magnetic flux that forms the magnetotail lobes (“dual lobe reconnection”). However, northward IMF is also favourable for the formation of a topologically closed structure in the magnetotail called a transpolar arc. We present direct observations of reconnection between the IMF and the magnetotail magnetic field close to a “wedge” of closed magnetotail field lines associated with a transpolar arc. When the lobe reconnection process is modified in this way, it leads to the opening of closed magnetotail flux associated with the transpolar arc. We also discuss the possible role of such a configuration in recently reported “non-lobe” high latitude reconnection events.
