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| Titel |
Polar observations of ion/electron bursts at the pre-dawn polar cap boundary: evidence for internal reconnection of overdraped lobe flux |
| VerfasserIn |
P. E. Sandholt, C. J. Farrugia |
| 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 ; 26, no. 8 ; Nr. 26, no. 8 (2008-08-04), S.2191-2202 |
| Datensatznummer |
250016178
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| Publikation (Nr.) |
 copernicus.org/angeo-26-2191-2008.pdf |
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| Zusammenfassung |
| Observations made by Polar of ion-electron bursts on the
dawn side of the polar cap are presented. They occurred when
conditions external to the magnetosphere corresponded to that of the
sheath region of a magnetic cloud, which was characterized by
very high densities/dynamic pressure and a magnetic field
which was strong in all components and which was tilted
antisunward (Bx<0) and northward (Bz>0)
with its
clock angle lying between 20 and 90°
(By: 8–15 nT).
A clear temporal development in the energy range spanned by
the individual ion bursts (from 0.2–2 keV to 1–10 keV) was present.
We relate this
to a corresponding temporal evolution in the cloud sheath field and plasma.
We analyze the solar wind-magnetosphere
aspects of the observations using the concepts of (i)
(i) overdraped lobe flux, (ii) Bx- and By-regulated
sequential reconnections
in opposite hemispheres (magnetopause and internal modes),
and (iii) newly-closed magnetic flux.
In particular, we find that the most energetic
ion bursts (accompanied by bi-directionally streaming electrons
at 1–10 keV and intense magnetosheath-origin fluxes)
are located on newly closed field lines
generated by internal reconnection occurring between overdraped
lobe field lines
and the closed geomagnetic field. This result
corroborates a topology of lobe reconnection under
conditions of dipole tilt and/or nonzero IMF Bx component advanced by
Watanabe et al. (2006), which in our case is adapted to
nonzero IMF By conditions. |
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