Abstract
AbstractAn algorithm to detect high‐speed ionospheric flow channels (FCs) in the polar cap was applied to data from the Longyearbyen radar of the Super Dual Auroral Radar Network. The Longyearbyen radar is at high latitude (78.2°N, 16.0°E geographic coordinates) and points northeast; therefore, it is in an ideal position for measuring zonal flows in the polar cap. The algorithm detected 998 events in the dayside polar cap region over 2 years of observations. The detected FCs typically were between 200 and 300 km latitudinal width, 1.1–1.3 km s−1 peak velocity, and 3 min in duration. The FC location shows an interplanetary magnetic field (IMF) By dependency, moving dawnward/duskward for a +By/−By. The FC monthly occurrence shows a bimodal distribution with peaks around the spring and autumn equinoxes, likely due to increased coupling between the solar wind‐magnetosphere‐ionosphere system at these times. The highest peak velocities show an absence of broad FC widths, suggesting that as the flow speed increases in the polar cap, the channels become more localized and narrow.
Highlights
The shape and flow strength of the large scale high-latitude plasma convection is strongly governed by the interplanetary magnetic field (IMF) (Cowley & Lockwood, 1992)
The majority of flow channels were detected on the dayside, with the densest population in the prenoon sector between 9 and 12 magnetic local time (MLT)
The small occurrence of nightside flow channels could be due to the field of view (FOV) of the radar being too far north in order to identify nightside reconnection-driven channels
Summary
The shape and flow strength of the large scale high-latitude plasma convection is strongly governed by the interplanetary magnetic field (IMF) (Cowley & Lockwood, 1992). Under southward IMF, magnetic reconnection occurs at the dayside subsolar point due to the merging of antiparallel magnetic fields. This reconnection drives antisunward flows across the polar cap, and reconnection in the Earth's magnetotail drives sunward return flows at lower, subauroral latitudes (Dungey, 1961). The resultant motion due to dayside and nightside reconnection under IMF Bz− conditions is visualized as a twin cell ionospheric convection pattern. The dayside convection throat and cusp are shifted postnoon, and the tension imposed on the field lines leads ionospheric flows with an westward component. For IMF By−, the orientation of the cells is reversed, the dayside convection throat and cusp are shifted prenoon, and the ionospheric flows have an eastward component
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