Fast-Moving Diffuse Auroral Patches: A New Aspect of Daytime Pc3 Auroral Pulsations
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 dayt...
| Main Authors: | , , , , , , |
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| Format: | Text |
| Language: | unknown |
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Merrimack ScholarWorks
2017
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| Subjects: | |
| Online Access: | https://scholarworks.merrimack.edu/phy_facpub/16 https://scholarworks.merrimack.edu/cgi/viewcontent.cgi?article=1015&context=phy_facpub |
| Summary: | 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. |
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