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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 31, issue 8
Ann. Geophys., 31, 1463–1483, 2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 31, 1463–1483, 2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 30 Aug 2013

Regular paper | 30 Aug 2013

Comparison between vortices created and evolving during fixed and dynamic solar wind conditions

Y. M. Collado-Vega1, R. L. Kessel2, D. G. Sibeck1, V. L. Kalb3, R. A. Boller4, and L. Rastaetter1 Y. M. Collado-Vega et al.
  • 1NASA Goddard Space Flight Center, Space Weather Laboratory, Code 674, Greenbelt, MD, USA
  • 2NASA Headquarters, SMD, Heliophysics Division, Washington, D.C., USA
  • 3NASA Goddard Space Flight Center, Terrestrial Information Systems Laboratory, Code 619, Greenbelt, MD, USA
  • 4NASA Goddard Space Flight Center, Science Data Systems Branch, Code 586, Greenbelt, MD, USA

Abstract. We employ Magnetohydrodynamic (MHD) simulations to examine the creation and evolution of plasma vortices within the Earth's magnetosphere for steady solar wind plasma conditions. Very few vortices form during intervals of such solar wind conditions. Those that do remain in fixed positions for long periods (often hours) and exhibit rotation axes that point primarily in the x or y direction, parallel (or antiparallel) to the local magnetospheric magnetic field direction. Occasionally, the orientation of the axes rotates from the x direction to another direction. We compare our results with simulations previously done for unsteady solar wind conditions. By contrast, these vortices that form during intervals of varying solar wind conditions exhibit durations ranging from seconds (in the case of those with axes in the x or y direction) to minutes (in the case of those with axes in the z direction) and convect antisunward. The local-time dependent sense of rotation seen in these previously reported vortices suggests an interpretation in terms of the Kelvin–Helmholtz instability. For steady conditions, the biggest vortices developed on the dayside (about 6 RE in diameter), had their rotation axes aligned with the y direction and had the longest periods of duration. We attribute these vortices to the flows set up by reconnection on the high-latitude magnetopause during intervals of northward Interplanetary Magnetic Field (IMF) orientation. This is the first time that vortices due to high-latitude reconnection have been visualized. The model also successfully predicts the principal characteristics of previously reported plasma vortices within the magnetosphere, namely their dimension, flow velocities, and durations.

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