Fast-moving diffuse auroral patches: A new aspect of daytime Pc3 auroral pulsations

Tetsuo Motoba, Yusuke Ebihara, Akira Kadokura, Mark J. Engebretson, Marc R. Lessard, Allan T. Weatherwax, Andrew Gerrard

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5 Scopus citations


Auroral pulsations are a convenient diagnostic of wave-particle interactions in the magnetosphere. A case study of a daytime Pc3 (22–100 mHz) auroral pulsation event, measured with a ~2 Hz sampling all-sky camera at South Pole Station (74.4°S magnetic latitude) on 17 May 2012, is presented. The daytime Pc3 auroral pulsations were most active in a closed field line region where the aurora was dominated by diffuse green-line emissions and within ±2 h of magnetic local noon. Usually, but not always, the corresponding periodic variations were recorded with a colocated search coil magnetometer. Of particular interest is the two-dimensional auroral signature, indicating that the temporal luminosity variations at a given point were due to repeated formation and horizontal motion of faint, nonpulsating auroral patches with scale sizes of ~100 km. The individual patches propagated equatorward with speeds of 15 km s−1 up to 20–25 km s−1 one after another along the magnetic meridian through local magnetic zenith. These properties differ considerably from typical pulsating aurorae, being periodic on-off luminosity variations in a particular auroral patch and drifting in accordance with the convection electric field in the magnetosphere. We speculate that such repetitive patterns of the fast-moving auroral patches, being another aspect of the daytime Pc3 auroral pulsations, may be a visible manifestation of compressional Pc3 waves which propagate earthward and cause modulation of precipitating keV electron fluxes in the dayside outer magnetosphere.

Original languageEnglish (US)
Pages (from-to)1542-1554
Number of pages13
JournalJournal of Geophysical Research: Space Physics
Issue number2
StatePublished - Feb 1 2017

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Geophysics


  • daytime auroral pulsations
  • outer magnetospheric dynamics
  • wave-particle interactions


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