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Related Concept Videos

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Magnetic Declination

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Source of the dayside cusp aurora.

S B Mende1, H U Frey1, V Angelopoulos2

  • 1Space Sciences Laboratory University of California Berkeley California USA.

Journal of Geophysical Research. Space Physics
|November 22, 2016
PubMed
Summary

Dayside cusp aurora, observed by Antarctic imagers and THEMIS satellites, is confirmed to be direct precipitation from the magnetosheath. Particle acceleration by dispersive Alfvén waves is identified as the likely cause of observed emissions.

Keywords:
cusp aurora

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Area of Science:

  • Space Physics
  • Auroral Physics
  • Magnetospheric Physics

Background:

  • Monochromatic all-sky imagers in Antarctica monitor auroral activity.
  • The Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission studies magnetospheric dynamics.

Purpose of the Study:

  • To investigate the origin of dayside cusp aurora using coordinated satellite and ground-based observations.
  • To determine the relationship between magnetopause crossings and ionospheric auroral emissions.

Main Methods:

  • Coordinated observations from Antarctic imagers and THEMIS satellites.
  • Magnetic field and plasma density measurements from THEMIS.
  • Ionospheric mapping using the Tsyganenko-96 field model.

Main Results:

  • Dayside cusp aurora (630 nm) is confirmed to be on open field lines, originating from magnetosheath precipitation.
  • Structured N2+ (427.8 nm) emissions indicate particle acceleration.
  • Magnetosheath particle energy and density correlate with N2+ emission intensity.
  • Dispersive Alfvén waves are the likely electron acceleration mechanism.

Conclusions:

  • Dayside cusp aurora is a direct consequence of magnetosheath particle precipitation onto open field lines.
  • Particle acceleration, likely by dispersive Alfvén waves, is crucial for generating observed auroral emissions.
  • A distinct hard-electron precipitation zone at lower latitudes originates within the magnetosphere.