According to the usual magnetopause reconnection model, plasma flows across the magnetopause current sheet, which is a rotational discontinuity with a nonzero normal magnetic field component Bn, from the magnetosheath into the magnetospheric boundary layer. As the plasma crosses the sheet, which has net current I, it is accelerated by the I¿Bn force and flows toward the poles with speeds up to twice the Alfv¿n speed.

In the past a number of ISEE magnetopause crossings in which such plasma jetting was observed have been interpreted in terms of reconnection, on the basis of a quantitative check of the tangential velocity and magnetic field changes across the magnetopause. In this paper we examine the total energy balance for two of these events (August 9 and September 8, 1978) with the objective of obtaining an additional check on the interpretation in terms of reconnection. The results are as follows: (1) To within experimental and other uncertainties the plasma and magnetic field data appear consistent with reconnection. (2) An enthalpy increase comparable to the kinetic energy increase occurs in the magnetopause. Thus substantial dissipation, which we believe to be viscous in nature, is present in the rotational discontinuity.

(3) During the September 8 event an ion heat flow associated with a beam of reflected magnetosheath particles carried away 10-20% of the total converted electromagnetic energy. (4) The energy balance is consistent with the previously inferred location of the ISEE spacecraft south of the reconnection line on August 9 and north of it on September 8, 1978. For a third event (December 4, 1977) examined here the magnetopause crossing occurred at a substantial northern latitude, but the plasma momentum change was equatorward rather than poleward, and there was little change in plasma kinetic energy. In this case we infer that normal magnetic field and flow components but no local reconnection electric field were present at the magnetopause.