Abstract
Abstract. Unsteady processes in the solar wind–magnetosphere interaction, such as vortices developed at the magnetopause boundary by the Kelvin–Helmholtz instability, may contribute to the process of mass, momentum and energy transfer into the Earth's magnetosphere. The research described in this paper validates an algorithm to automatically detect and characterize vortices based on velocity data from simulations. The vortex identification algorithm (VIA) systematically searches the 3-D velocity fields to identify critical points where the magnitude of the velocity vector vanishes. The velocity gradient tensor is computed and its invariants are used to assess vortex structure in the flow field. We use the Community Coordinated Modeling Center (CCMC) Runs on Request capability to create a series of model runs initialized from the conditions observed by the Cluster mission in the Hwang et al. (2011) analysis of Kelvin–Helmholtz vortices observed during southward interplanetary magnetic field (IMF) conditions. We analyze further the properties of the vortices found in the runs, including the velocity changes within their motion across the magnetosheath. We also demonstrate the potential of our tool to identify and characterize other transient features (e.g., flux transfer events, FTEs) with vortical internal structures. We find that the vortices are associated with flows on the magnetosheath side of the magnetopause that reach speeds greater than the solar wind speed at the bow shock. Keywords. Magnetospheric physics (MHD waves and instabilities; solar wind–magnetosphere interactions) – space plasma physics (numerical simulation studies)
Highlights
Large eddy structures or vortices can mark regions of intense flow activity and are important in understanding physical transport processes
We found that our tool could identify such features of flux transfer events (FTEs) due to their vortical structure in the simulation
The large data sets that are available through magnetospheric simulations and spacecraft missions require an automated search algorithm to focus on specific areas or features such as transients on the magnetopause boundary
Summary
Large eddy structures or vortices can mark regions of intense flow activity and are important in understanding physical transport processes. A second study, Collado-Vega et al (2013), used the first stages of the automated approach to analyze vortex development when the IMF abruptly switched from southward to northward with other solar wind conditions fixed. This was the first time that vortices formed during high-latitude reconnection were visualized. The fast data characterization and vortex detection made possible with this algorithm will permit the researcher to identify magnetosphere locations for further investigation in large simulation output data sets This saves time, and diminishes the potential for missing features of interest.
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