Signatures in the dayside aurora of plasma transfer from the magnetosheath

Abstract

Continuous ground‐based observations of the dayside aurora provide important information, complementary to the in situ measurements from satellites, on plasma transport and electromagnetic coupling between the magnetosheath and the magnetosphere. In this study, observations of the polar cusp/dayside oval aurora from Svalbard and simultaneous observations of the nightside aurora from Poker Flat, Alaska, and the interplanetary magnetic field from satellites are used to identify the ionospheric signatures of plasma transfer from the solar wind to the magnetosphere. The characteristics of motion, spatial scale, time of duration, and repetition frequency of certain day side auroral forms which occur at the time of large‐scale oval expansions (interplanetary magnetic field B z < 0) are observed to be consistent with the expected optical signatures of plasma transfer through the dayside magnetopause boundary layer, associated with flux transfer events. Similarly, more large‐scale (time and space) events are tentatively explained by the quasi steady state reconnection process.