Traveling convection vortices as seen by the SuperDARN HF radars

Details Traveling convection vortices as seen by the SuperDARN HF radars Traveling convection vortices as seen by the SuperDARN HF radars

Feb 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999jgr...104.2591l&link_type=abstract

Journal of Geophysical Research, Volume 104, Issue A2, p. 2591-2602

Physics

9

Ionosphere: Ionosphere/Magnetosphere Interactions, Ionosphere: Electric Fields, Magnetospheric Physics: Magnetopause, Cusp, And Boundary Layers, Magnetospheric Physics: Magnetosphere/Ionosphere Interactions

Scientific paper

Two impulsive traveling convection vortex (TCV) events observed simultaneously by ground based magnetometers and the SuperDARN HF radars in the prenoon sector were studied. In both cases, disturbances traveled westward at speeds of 4-6 km/s. Convection patterns derived from magnetometer measurements and radar observations were overall in reasonable agreement; observed differences at some points might be caused by both the nonuniform ionospheric conductivity distribution and difference in the integration time of the radar and magnetometer data. For one event, the convection patterns obtained from magnetometer data and SuperDARN radar measurements were relatively simple; they can be interpreted as a result of the westward motion of a convection vortex system associated with a pair of field-aligned currents separated in azimuthal direction. This TCV event was associated with relatively low Pc5 pulsation activity, contrary to the second TCV event that was accompanied by a train of Pc5 magnetic pulsations of large amplitude. Convection patterns for the second event were complicated. A simple scenario for the interpretation of the generation of TCVs and Pc5 pulsations is suggested. A sudden impulse in the solar wind dynamic pressure produces disturbances on several boundaries of magnetospheric plasma: on the magnetopause, the LLBL inner edge, and the plasma sheet inner edge. These boundaries are elastic so that surface waves can propagate along them. The high-latitude wave is responsible mainly for TCVs, whereas the low-latitude waves may be responsible for excitation of Pc5 field line resonance pulsations. The scenario explains important features of both TCV events and Pc5 pulsations: both phenomena appear simultaneously and show westward (eastward) propagation, but the TCVs are observed at latitudes close to the LLBL inner edge, whereas the Pc5 pulsations occur at lower latitudes, close to the inner boundary of the plasma sheet.

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