Dynamics Explorer Measurements of Particles, Fields, and Plasma Drifts Over a Horse-Collar Auroral Pattern.

Sharber, J. R.; Hones, E. W.; Heelis, R. A.; Craven, J. D.; Frank, L. A.; Maynard, N. C.; Slavin, J. A.; Birn, J.

doi:10.5636/jgg.44.1225

Cited by 6 publications

(2 citation statements)

References 20 publications

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“…The detection algorithm used to identify the TPAs works by identifying the peak in average radiance intensity above 12.5° colatitude and as such will always identify the location based on the brightest arc which in the case of the HCA is usually the dawn arc. The HCA events studied by Sharber et al (1992) supports this. Their event which occurred on 2nd December 1981 and was imaged between 14:21 and 15:46 UT by DE-1 first clearly showed the well-defined dawnside web and arc feature with the duskside not being clear until 15:10 UT, although they note that the general pattern is present throughout the period.…”

Section: Hca Morphology and Relation To Tpassupporting

confidence: 65%

“…The HCA events studied by Sharber et al. (1992) supports this. Their event which occurred on 2nd December 1981 and was imaged between 14:21 and 15:46 UT by DE‐1 first clearly showed the well‐defined dawnside web and arc feature with the duskside not being clear until 15:10 UT, although they note that the general pattern is present throughout the period.…”

Section: Discussionmentioning

confidence: 62%

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Occurrence Statistics of Horse Collar Aurora

et al. 2022

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Horse collar aurora (HCA) are an auroral feature where the dawn and dusk sector auroral oval moves polewards and the polar cap becomes teardrop shaped. They form during prolonged periods of northward interplanetary magnetic field (IMF), when the IMF clock angle is small. Their formation has been linked to dual‐lobe reconnection (DLR) closing magnetic flux at the dayside magnetopause. The conditions necessary for DLR are currently not well‐understood therefore understanding HCA statistics will allow DLR to be studied in more detail. We have identified over 600 HCA events between 2010 and 2016 in UV images captured by the Special Sensor Ultraviolet Spectrographic Imager instrument on‐board the Defense Meteorological Satellite Program spacecraft F16, F17 and F18. As expected, there is a clear preference for HCA occurring during northward IMF. We find no clear seasonal dependence in their occurrence, with an average of 8 HCA events per month. The occurrence of HCA events does not appear to depend on the Bx component of the IMF. Considering the average radiance intensity across the dusk‐dawn meridian shows the HCA as a separate bulge inside the auroral oval and that the dawn side arc of the HCA is usually brighter than the dusk in the Lyman‐Birge‐Hopfield short band. We relate this to the expected field aligned current pattern of HCA formation. We further suggest that transpolar arcs observed in the dawn sector simultaneously in both northern and southern hemispheres are misidentified HCA.

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Section: Hca Morphology and Relation To Tpassupporting

confidence: 65%

Section: Discussionmentioning

confidence: 62%