Physics
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sm61a03c&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #SM61A-03 INVITED
Physics
2407 Auroral Ionosphere (2704), 2409 Current Systems (2708), 2724 Magnetopause, Cusp, And Boundary Layers, 2736 Magnetosphere/Ionosphere Interactions, 2784 Solar Wind/Magnetosphere Interactions
Scientific paper
We report results from a statistical study of high latitude traveling convection vortices measured by the West Coast Greenland Magnetometer chain during the year 1996. Events for the study were selected from 20-second data using a data fitting procedure which identifies mesoscale vortex-like structures in the ionospheric current distribution measured by the magnetometer chain. For an event to be selected, we required 8 continuous measurements where the variations of the fit parameters between two successive time points are small (variations of the field-aligned current I do not exceed 50 kA, and variations of the x and y positions of the vortex center do not exceed 200 km). To ensure that the ionospheric current forms a vortex-like structure, the additional requirement is imposed that stations to the north and south of the vortex center must have H-component variations of opposite sign. For each vortex, the average value of the field-aligned current and vortex speed (northward and eastward) are computed. We have obtained a list of about 22000 vortices with average field-aligned current greater than 20 kA, corresponding to magnetic variations greater than 10 nT observed between 06 and 18 MLT. If we restrict the analysis to vortices with current greater than 50 kA, we have 3900 events. Our analysis investigates the dependence of vortex occurrence and motion on Local Time, solar wind and interplanetary magnetic field parameters. Among our results, we find the best correlation between TCV occurrence and solar wind speed. A strong relationship between occurrence and negative IMF Bz as well as the variance of the IMF is also found. In the noon sector, positive IMF By is associated with westward TCV motion and negative IMF By is associated with eastward TCV motion. Negative IMF Bz appears to slow the northward TCV speed, however positive IMF Bz shows no affect on TCV speed. We interpret the results in terms of Kelvin-Helmholtz generation mechanisms, magnetic reconnection generation mechanisms, and pressure change generation mechanisms.
Clauer Robert C.
Petrov V. G.
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