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Magnetospheric solitary structure maintained by 3000 km/s ions as a cause of westward moving auroral bulge at 19 MLT
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2009 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, no 7, 2947-2969 p.Article in journal (Refereed) Published
Abstract [en]

In the evening equatorial magnetosphere at about 4 R-E geocentric distance and 19 MLT, the four Cluster spacecraft observed a solitary structure with a width of about 1000 similar to 2000 km in the propagation direction. The solitary structure propagates sunward with about 5 similar to 10 km/s carrying sunward electric field (in the propagation direction) of up to about 10 mV/m (total potential drop of about 5 similar to 10 kV), depletion of magnetic field of about 25%, and a duskward E x B convection up to 50 km/s of He+ rich cold plasma without O+. At the same time, auroral images from the IMAGE satellite together with ground based geomagnetic field data showed a westward (sunward at this location) propagating auroral bulge at the magnetically conjugate ionosphere with the solitary structure. The solitary structure is maintained by flux enhancement of selectively 3000 km/s ions (about 50 keV for H+, 200 keV for He+, and 750 keV for O+). These ions are the main carrier of the diamagnetic current causing the magnetic depletion, whereas the polarization is maintained by different behavior of energetic ions and electrons. Corresponding to aurora, field-aligned accelerated ionospheric plasma of several keV appeared at Cluster from both hemispheres simultaneously. Together with good correspondence in location and propagation velocity between the auroral bulge and the solitary structure, this indicates that the sunward moving auroral bulge is caused by the sunward propagation of the solitary structure which is maintained by energetic ions. The solitary structure might also be the cause of Pi2-like magnetic variation that started simultaneously at Cluster location.

Place, publisher, year, edition, pages
2009. Vol. 27, no 7, 2947-2969 p.
Keyword [en]
Magnetospheric physics, Auroral phenomena, Electric fields, Energetic, particles, trapped, storm-substorm relationship, field-aligned currents, ring current, traveling surge, satellite measurements, pi-2 pulsations, radiation, belts, electric-field, cluster, dynamics
URN: urn:nbn:se:kth:diva-18656ISI: 000268622700030ScopusID: 2-s2.0-75149180883OAI: diva2:336703
QC 20100525Available from: 2010-08-05 Created: 2010-08-05Bibliographically approved

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Lindqvist, Per-Arne
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Space and Plasma Physics
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