Bursts of Pc 1‐2 near the ionospheric footprint of the cusp and their relationship to flux transfer events

Authors:
  • RARoger L. Arnoldy
    Roger L. Arnoldy
  • MEM. J. Engebretson
    M. J. Engebretson
  • LCL. J. Cahill
    L. J. Cahill
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Abstract
Ground‐based induction antennas at high latitudes measure a magnetic signature which can be modeled as the ground signature of a moving, large vortex of ionospheric Hall current. This Hall current is believed to be generated by the field‐aligned current in a helical flux tube that has been reconnected: a flux transfer event (FTE). These possible FTEs are seen predominantly by ground stations near the dayside cusp, although similar signatures can be found near the plasmapause and in the polar cap. A significant result obtained from the induction antennas is that for about 60% of the cusp FTEs there are coincident Pc 1–2 pulsations. If the FTE‐coincident Pc 1–2 pulsations are produced by ion cyclotron resonance, the energy of the streaming hot ion population can be estimated and is found to be consistent with midaltitude spacecraft measurements and sounding rocket data. Pc 1–2 pulsations measured near the plasmapause which occur simultaneously with the cusp Pc 1–2 coincident with FTEs pose some questions about the generation of the Pc 1–2 and whether the FTE signatures may not simply be the result of solar wind pressure impulses on the magnetopause.

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