Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations

• Published in: Annales Geophysicae
• Main Authors: Senior, C., Cerisier, J.-C., Rich, F., Lester, M., Parks, G. K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2002
• Subjects: article; Verlagsveröffentlichung; Iceland
• Online Access: https://doi.org/10.5194/angeo-20-771-2002; https://noa.gwlb.de/receive/cop_mods_00035963; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00035917/angeo-20-771-2002.pdf; https://angeo.copernicus.org/articles/20/771/2002/angeo-20-771-2002.pdf

High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF). Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended regions of auroral particle precipitation from the magnetospheric boundaries. A DMSP pass over the Iceland-West field-of-view while one of these sporadic bursts of enhanced flow is observed, indicates that the flow bursts appear within the plasma sheet and at its outward edge, which excludes Kelvin-Helmholtz instabilities at the magnetopause boundary as the generation mechanism. In the nightside region, the precipitation is more spot-like and the convection organizes itself as clockwise U-shaped structures. We interpret these flow bursts as the convective transport following plasma injection events from the tail into the night-side ionosphere. We show that during this period, where the IMF clock angle is around 70°, the dayside magnetosphere is not completely closed. Key words. Ionosphere (Auroral ionosphere; Ionospheremagnetosphere interactions; Particle precipitation)