Solar wind modulation of cusp particle signatures and their associated ionospheric flows

Abstract

This paper presents a multi‐instrument case study of the northern polar cusp at a variety of altitudes in conjunction with solar wind measurements. In the midaltitude cusp the Polar spacecraft observed pulsed particle and magnetic field signatures with periodicities ranging from ∼5 to 40 min for over 3 hours. Simultaneously, the CUTLASS HF radars measured poleward moving radar auroral forms (PMRAFs) with inter‐PMRAF periods similar to the Polar periodicities but several degrees of magnetic latitude poleward of the ionospheric footprint of the spacecraft. Such PMRAFs have previously been identified as ionospheric signatures of transient reconnection and flux transfer events. During this event, both the ACE and Wind spacecraft were making measurements in the solar wind. Oscillations in the time‐shifted solar wind magnetic fields and flows and calculated reconnection electric fields were observed with the same periodicities as those seen by Polar and CUTLASS. We conclude that the solar wind Alfvén waves modulate the dayside interaction, producing periodic flux transfer events resulting in the pulsed cusp particle signatures and PMRAFs. This study is the first observation of solar wind driven pulsed cusp particle signatures and associated PMRAFs, i.e., at both magnetospheric and ionospheric altitudes, at multiple simultaneous discrete periodicities.