Localized Reconnection and Plasma Structures at the Magnetopause

The magnetopause current sheet is known to have a thickness comparable to an ion gyro-radius/skin depth and such processes while neglected in MHD are the focal point to multi-spacecraft missions such as THEMIS and Cluster. Multi-fluid/multi-scale modeling is used to examined the structure of magnetopause down to a resolution of 200-300 km. Attention is focused on southward interplanetary magnetic field (IMF) and when there is a non- zero component IMF By. It is shown that with the inclusion of ion gyro-radius/skin depth the reconnection on the magnetopause is very patchy, with a significant (10-20 nT) core magnetic field being generated by the Hall term in the generalized Ohm's law, that is orthogonal to the incident IMF (even when IMF By is non-zero). This magnetic field component means that the question of whether the reconnection is parallel or component is not well posed because the core magnetic field modifies the overall structure of the magnetopause. It is shown though that the strongest acceleration of particles occurs within the vicinity of the subsolar region through with the reconnection being localized to structures less that 0.5 Re in width, a few Re in breadth and varying in time and space. A comparison of the signatures of this reconnection is made between equator and polar orbiting spacecraft.