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| Titel |
Interhemispheric comparison of spectral width boundary as observed by SuperDARN radars |
| VerfasserIn |
K. Hosokawa, E. E. Woodfield, Mark Lester, S. E. Milan, N. Sato, A. S. Yukimatu, T. Iyemori |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 21, no. 7 ; Nr. 21, no. 7, S.1553-1565 |
| Datensatznummer |
250014662
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| Publikation (Nr.) |
 copernicus.org/angeo-21-1553-2003.pdf |
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| Zusammenfassung |
Previous studies have
shown that dayside equatorward edge of coherent HF radar backscatter having
broad Doppler spectral width is coincident with the equatorward edge of the
cusp particle precipitation. This enables the boundary between broad and narrow
spectral width backscatters (spectral width boundary) in the dayside magnetic
local time sector to be used as a proxy for the open/closed field line
boundary. The present case study employs magnetically conjugate SuperDARN
coherent HF radars to make an inter-hemispheric comparison of the location and
variation of the spectral width boundaries. Agreement between the magnetic
latitudes of the boundaries in both hemispheres is remarkable. Correlation
coefficients between the latitudes of the boundaries are larger than 0.70.
Temporal variation of the spectral width boundary follows the same equatorward
trend in both hemispheres. This is consistent with the accumulation of open
flux in the polar cap by dayside low-latitude magnetopause reconnection,
expected when IMF Bz is negative. Boundaries in both hemispheres
also exhibit short-lived poleward motions superposed on the general
equator-ward trend, which follows the onset of substorm expansion phase and a
temporary northward excursion of IMF Bz during substorm recovery
phase. There is an interhemispheric difference in response time to the substorm
occurrence between two hemispheres. The spectral width boundary in the Southern
Hemisphere starts to move poleward 10 min earlier than that in the Northern
Hemisphere. We discuss this difference in terms of interhemispheric asymmetry
of the substorm breakup region in the longitudinal direction associated with
the effect of IMF By.
Key words. Ionosphere
(ionosphere-magnetosphere interactions; plasma convection) – Magnetospheric
physics (magnetopause, cusp, boundary layers) |
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