THE EFFICIENCY OF VISCOUS INTERACTION BETWEEN THE SOLAR-WIND AND THE MAGNETOSPHERE DURING INTENSE NORTHWARD IMF EVENTS

We examined 11 cases when the interplanetary magnetic field (IMF) was intensely northward (> 10 nT) for long durations of time (> 3 hours), to quantitatively determine an upper limit on the efficiency of solar wind energy injection into the magnetosphere. We have specifically sel ected these large BN events to minimize the effects of magnetic reconn ection. Many of these cases occurred during intervals of high-speed st reams associated with coronal mass ejections when viscous interaction effects might be at a maximum. It is found that the typical efficiency of solar wind energy injection into the magnetosphere is 1.0 x 10(-3) to 4.0 x 10(-3), 100 to 30 times less efficient than during periods o f intense southward IMFs. Other energy sinks not included in these num bers are discussed. Estimates of their magnitudes are provided.