Polar and Cluster observations of a dayside inverted-V during conjunction

Abstract

We investigate particle and fields data during a conjunction of the Polar and Cluster spacecraft. This conjunction occurs near the dayside cusp boundary layer when a dayside inverted-V was observed in the particle data of both satellites. Electron, ion, electric field, and magnetic field data from each satellite confirm that the dayside inverted-V (DSIV) structure is present at the location of both satellites and the electric fields persist from the altitude of the Polar (lower) spacecraft to the altitude of the Cluster spacecraft. We observe accelerated, precipitating electrons and upward ions along the magnetic field. In addition, large amplitude electric fields perpendicular to the ambient magnetic field seen by Polar and by Cluster suggest significant parallel electric fields associated with these events. For similar DSIV events observed by the Polar spacecraft, plasma waves (identified as possible Alfvén waves) have been observed to propagate in both directions along the magnetic field line. Future conjunctions will be necessary to confirm that DSIVs are associated with reconnection sites.