Dayside moving auroral forms and bursty proton auroral events in relation to particle boundaries observed by NOAA 12

Abstract

This paper consider two sequences of moving auroral forms that were observed in the early postnoon sector above Svalbard. The series of events observed on January 12, 1992, moved westward (noonward) under unknown IMF conditions. The events observed on December 17, 1992, moved eastward while interplanetary magnetic field BY was strongly negative. The auroral luminosity for these events was dominated by the 630.0-nm emission line but correlated in space and time with subvisual Hβ intensifications. NOAA 12 particle characteristics relate the moving auroral forms to low-latitude boundary layer precipitation located poleward of the electron trapping boundary, i.e., on open magnetic field lines. The auroral activity and associated particle signatures are both attributed to magnetopause reconnection. Since magnetic reconnection is the only known mechanism capable of bulk injecting magnetosheath ions and electrons on the dayside, we suggest that simultaneous occurrence of proton and electron auroral activity is a unique footprint of dayside magnetic reconnection. Copyright 1998 by the American Geophysical Union.