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On a possible connection between the longitudinally propagating near‐Earth plasma sheet and auroral arc waves: A reexamination
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| Zeitschriftentitel: | Journal of Geophysical Research: Space Physics |
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| Personen und Körperschaften: | , , , |
| In: | Journal of Geophysical Research: Space Physics, 120, 2015, 1, S. 432-444 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
American Geophysical Union (AGU)
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| Schlagwörter: |
| Zusammenfassung: | <jats:title>Abstract</jats:title><jats:p>Azimuthally propagating low‐frequency waves (or wavy structures) often occur in a localized region of the near‐Earth plasma sheet and auroral arc immediately prior to auroral breakup. Although both are believed to be magnetospheric and ionospheric manifestations of a plasma sheet instability that may lead to substorm onset, the fundamental coupling processes behind their relationship are not yet understood. To address this question, we reexamined in detail a fortuitous conjunction event of prebreakup near‐Earth plasma sheet and auroral arc waves, initially reported by Uritsky et al. (2009) using the Time History of Events and Macroscale Interactions during Substorms space‐ground observations. The event exhibited a morphological one‐to‐one association between longitudinally propagating arc wave (LPAW) in the ionosphere and Pi2/Pc4 range wave activity in the plasma sheet. Our analysis revealed that (1) the LPAW was the periodic luminosity modulation of the growth phase arc by faint, diffuse, green line‐dominated auroral patches propagating westward along/near the arc, rather than some type of small‐scale arc structuring, such as auroral beads/rays/undulations; and (2) the plasma sheet wave, which had a diamagnetic nature, propagated duskward with accompanying coincident modulation of field‐aligned fluxes of 0.1–30 keV electrons. These findings suggest that the LPAW was likely connected to the plasma sheet wave via modulated diffuse precipitation of hard plasma sheet electrons (> ~1 keV), not via filamentary field‐aligned currents, as expected from the ballooning instability regime. Another potential implication is that such prebreakup low‐frequency wave activity in the near‐Earth plasma sheet is not necessarily guaranteed to initiate prebreakup auroral arc structuring.</jats:p> |
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| Umfang: | 432-444 |
| ISSN: |
2169-9402
2169-9380 |
| DOI: | 10.1002/2014ja020694 |