Introduction

Solar influences on ionospheric plasma outflows have significant potential impacts on the nightside plasma sheet via a transport route through the polar caps and into the mid-tail plasma sheet, as observed by Orsini et al. [1982] and modeled by Cladis [1986]. The association of ionospheric outflow mass flux enhancements with geomagnetic activity (Kp index) and with solar EUV activity (solar EUV proxy, the 10.7cm microwave flux, F10.7) have been well-established for some time [Yau et al., 1985]. The association with F10.7 has been shown to result from the enhancement of neutral oxygen density in the topside ionosphere, at the expense of the neutral hydrogen density [Cannata et al., 1989]. The association with Kp suggests a relationship to enhancement of nightside auroral activity. However, the largest fluxes of heavy ion escape originate from the dayside auroral zone [Yau et al., 1985, , ], and the dayside aurora responds more directly to solar wind conditions [Liou et al., 1998].

A survey of cleft plasma outflow properties was presented by Pollock et al. [1990]. It found a close association with the cusp region of field-aligned currents, and a strong correlation (R=0.72) between the hourly averaged value of interplanetary Bz and the invariant latitude of peak upward O flux. Surprisingly, no significant correlation (R -0.14) was found between the interplanetary magnetic field (Bz) and the flux of plasma upwelling. A good correlation has been reported between the occurrence frequency of dayside upwelling and the solar wind dynamic pressure by Giles [1993]. However, no published accounts have related the outflow flux to solar wind drivers. With this in mind, we report here a particularly dramatic example of interplanetary effects, and place it in a context provided by statistical results from the DE-1/ISEE-1 data sets.