Abstract
Recent observations in the vicinity of the dayside magnetopause have led to much new information concerning the interactions between magnetosheath and magnetospheric plasma which lead to large-scale magnetospheric convection. In this paper the boundary observations are reviewed, and compared both with theoretical suggestions and with requirements imposed by measurements of the total transpolar voltage at low altitudes. It is concluded that (a) magnetic reconnection probably plays a dominant role in driving convection when IMF Bz is negative, the limited observational evidence being consistent with reconnection-associated phenomena generating voltages of several tens of kV as required by the low altitude observations; (b) when IMF Bz is positive, boundary processes appear to be compatible with generating -10-20kV background voltages as also observed at low altitudes, though the nature of the boundary interaction process remains unclear, and (c) recent observations at low altitudes in the vicinity of the dayside cusp contain evidence for impulsive phenomena occurring at the dayside magnetopause boundary, which are consistent with expectations based on reconnection-associated flux transfer events as opposed to the “impulsive penetration” picture.
