| Volumes and Issues Contents of Issue 8 |
www.ann-geophys.net/27/3043/2009/
doi:10.5194/angeo-27-3043-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Foreshock-like density cavity in the outflow region of magnetotail reconnection
1University of Toulouse, UPS, CESR, 9 avenue colonel Roche, 31028 Toulouse cedex 4, France
2CNRS, UMR5187, 31028 Toulouse, France
3State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Beijing 100080, China
4School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
5Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA
6Centre d'Etudes des Environnements Terrestre et Planétaires, Centre National de la Recherche Scientifique, 78140 Vélizy, France
Abstract. During Cluster spacecraft crossing of the magnetotail, a novel density depleted cavity in association with magnetic compressions in the outflow region of reconnection was observed. It contains intense reflected field-aligned particles, which are produced by a generation mechanism similar to that of the terrestrial foreshock, and hence manifests a foreshock-like morphology. In this cavity, reflected field-aligned proton beams were observed and simultaneously the feature of magnetic-mirror loss-cone proton distributions were found. Magnetic field fluctuations, especially quasi-monochromatic oscillations, were recorded. Both the leading egde and the ULF wave boundary of the ion foreshock are identified from the time sequence of proton and magnetic field observations. Just upstream of the leading egde of the ion foreshock, reflected field-aligned electrons were detected, whose distribution has a narrow bump-on-tail pattern. However, close to the shock front, reflected electrons with a broad bump-on-tail pattern was measured. These two different manifestations of reflected electrons reveal the differences in their microscopic physics of the reflecting process. Moreover, a part of incident ions was further accelerated in the cavity due to trans-time magnetic pumping which provides another possible mechanism in the multi-step acceleration processes in reconnection.
Full Article (PDF, 3693 KB)
Citation: Cai, C. L., Dandouras, I., Rème, H., Cao, J. B., Zhou, G. C., Parks, G. K., and Fontaine, D.: Foreshock-like density cavity in the outflow region of magnetotail reconnection, Ann. Geophys., 27, 3043-3053, doi:10.5194/angeo-27-3043-2009, 2009. Bibtex EndNote Reference Manager XML
