Coordinated ground-based, low altitude satellite and Cluster observations on global and local scales during a transient post-noon sector excursion of the magnetospheric cusp

Abstract

Abstract. On 14 January 2001, the four Cluster spacecraft passed through the northern magnetospheric mantle in close conjunction to the EISCAT Svalbard Radar (ESR) and approached the post-noon dayside magnetopause over Greenland between 13:00 and 14:00 UT. During that interval, aCorrespondence to: H. J. Opgenoorth (opg@irfu.se) sudden reorganisation of the high-latitude dayside convection pattern accurred after 13:20 UT, most likely caused by a direction change of the Solar wind magnetic field. The result was an eastward and poleward directed flow-channel, as monitored by the SuperDARN radar network and also by arrays of ground-based magnetometers in Canada, Greenland and Scandinavia. After an initial eastward and later 1368 H. J. Opgenoorth et al.: Cluster and ground-based observations of a transient cusp event poleward expansion of the flow-channel between 13:20 and 13:40 UT, the four Cluster spacecraft, and the field line footprints covered by the eastward looking scan cycle of the Söndre Strömfjord incoherent scatter radar were engulfed by cusp-like precipitation with transient magnetic and electric field signatures. In addition, the EISCAT Svalbard Radar detected strong transient effects of the convection reorganisation, a poleward moving precipitation, and a fast ion flowchannel in association with the auroral structures that suddenly formed to the west and north of the radar. From a detailed analysis of the coordinated Cluster and ground-based data, it was found that this extraordinary transient convection pattern, indeed, had moved the cusp precipitation from its former pre-noon position into the late post-noon sector, allowing for the first and quite unexpected encounter of the cusp by the Cluster spacecraft. Our findings illustrate the large amplitude of cusp dynamics even in response to moderate solar wind forcing. The global ground-based data proves to be an invaluable tool to monitor the dynamics and width of the affected magnetospheric regions.

Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate

“…An association between patches and transient reconnection pulses has been suggested by a number of recent studies Lockwood et al, 2000Opgenoorth et al, 2001;Moen et al, 2001). Other studies suggest patches are linked to other phenomena, such as travelling convection vortices (Valladares et al, 1994(Valladares et al, , 1999.…”

“…They are seen moving poleward into the polar cap on the dayside (Foster and Doupnik, 1984;Foster, 1989;Lockwood and Carlson, 1992;Opgenoorth et al, 2001;Carlson et al, 2002, moving across the central polar cap (Weber et al,1984;Anderson et al, 1988;Sojka et al, 1993Sojka et al, , 1994McEwen and Harris, 1996;Pedersen, 2000), and emerging from the polar cap into the nightside auroral oval (Lockwood and Carlson, 1992). In many studies, patches have been associated with regions of enhanced HF radar backscatter and so linked with the poleward-moving events seen by these radars (Rodger et al, 1994a, b;Milan et al, 2000;Davies et al, 2002).…”

“…In this model, lower-concentration flux tubes arise from local times further away from noon and, once in the polar cap, they form the equatorward part of each patch of newly-opened flux generated by a reconnection pulse. Combined observations by the EISCAT Svalbard Radar (ESR) with the EISCAT VHF and CUTLASS radars and by the ESR with the Cluster and DMSP spacecraft (Opgenoorth et al, 2001) provide evidence for this mechanism. Furthermore, fast azimuth scans by the ESR have shown plasma enhancements propagating into the polar cap (Carlson et al, 2002).…”

Cluster observations of a structured magnetospheric cusp

“…The data have also revealed the existence of a double cusp structure, and field-aligned currents and plasma instabilities in the cusp (e.g. Bosqued et al, 2001;Krauklis et al, 2001;Gurnett et al, 2001;Taylor et al, 2001;Decreau et al, 2001;Opgenoorth et al, 2001;Pitout et al, 2001;Réme et al, 2001;Cornilleau et al, 2003). Recently, Cargill et al (2005) presented a review of Cluster at the magnetospheric cusps.…”

The Chinese ground-based instrumentation in support of the combined Cluster/Double Star satellite measurements

“…Opgenoorth and Lockwood (1997) have discussed ways to support the multipoint insitu satellite measurements and presented a number of potentially useful configurations between the satellites and any one ground-based observatory. A number of papers have been published since Cluster launched to show how the combined spacecraft and ground-based observation could help to shed light on outstanding questions in magnetospheric physics (Opgenoorth et al, 2001;Lockwood et al, 2001a, b;Moen et al, 2001). …”