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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
Sprache Englisch
ISSN 0992-7689
Digitales Dokument URL
Erschienen In: Annales Geophysicae ; 26, no. 8 ; Nr. 26, no. 8 (2008-08-04), S.2191-2202
Datensatznummer 250016178
Publikation (Nr.) Volltext-Dokument vorhandencopernicus.org/angeo-26-2191-2008.pdf
 
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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