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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 30, issue 3
Ann. Geophys., 30, 537-544, 2012
https://doi.org/10.5194/angeo-30-537-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 30, 537-544, 2012
https://doi.org/10.5194/angeo-30-537-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 16 Mar 2012

Regular paper | 16 Mar 2012

A plasma flow vortex in the magnetotail and its related ionospheric signatures

C. L. Tang C. L. Tang
  • 1Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University at Weihai, Weihai, Shandong, 264209, China
  • 2Sate Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, China

Abstract. We presented a large-scale plasma flow vortex event that occurred on 1 March 2009 observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. During the interval, THEMIS satellites were located in the premidnight region between 11 and 16 RE downtail. Dawnward-earthward plasma flows were seen initially in the magnetotail, followed by duskward-tailward flows. This suggests that a clockwise plasma flow vortex (seen from above the equatorial plane) was observed on the dawn side of the plasma sheet. Furthermore, high energy (>1 keV) electrons were observed. Auroral images at 427.8 nm and THEMIS white light all-sky imager (ASI) at Fort Smith showed a discrete auroral patch formed at the poleward of the auroral oval, it then intensified. It extended eastward and equatorward first and followed by westward motion to form the clockwise auroral vortex. The auroral feature corresponded to the ionospheric signatures of the plasma flow vortex in the magnetotail when the Alfvén transit time between the magnetotail and the ionosphere was taken into account. We suggest that the large-scale clockwise plasma flow vortex in association with the high energy (>1 keV) electrons on the dawn side of the plasma sheet generated a downward field-aligned current (FAC) that caused the related ionospheric signatures. The plasma flow vortex had rotational flow speeds of up to 300 km s−1. The current density associated with the plasma flow vortex was estimated at 2.0 μA m−2, mapped to the ionosphere.

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