Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobeReportar como inadecuado

Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobe - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

1 Solar Terrestrial Physics Division 2 Department of Physics and Astronomy 3 IRF 4 EISCAT Scientific Association 5 MSSL - Mullard Space Science Laboratory 6 CESR - Centre d-étude spatiale des rayonnements 7 Space Vehicles Directorate 8 University of Calgary 9 Remote Sensing Group 10 HAO - High Altitude Observatory 11 FMI - Finnish Meteorological Institute 12 University of California 13 University of Tromso 14 Communications Research Centre 15 Blackett Laboratory 16 Department of Physics Oslo 17 Department of Physics Minneapolis 18 DMI - Danish Meteorological Institute 19 Istituto di Fisica dello Spazio Interplanetario

Abstract : During the interval between 8:00–9:30 on 14 January 2001, the four Cluster spacecraft were moving from the central magnetospheric lobe, through the dusk sector mantle, on their way towards intersecting the magnetopause near 15:00 MLT and 15:00 UT. Throughout this interval, the EISCAT Svalbard Radar ESR at Longyearbyen observed a series of poleward-moving transient events of enhanced F-region plasma concentration -polar cap patches-, with a repetition period of the order of 10 min. Allowing for the estimated solar wind propagation delay of 75 ± 5 min, the interplanetary magnetic field IMF had a southward component during most of the interval. The magnetic footprint of the Cluster spacecraft, mapped to the ionosphere using the Tsyganenko T96 model with input conditions prevailing during this event, was to the east of the ESR beams. Around 09:05 UT, the DMSP-F12 satellite flew over the ESR and showed a sawtooth cusp ion dispersion signature that also extended into the electrons on the equatorward edge of the cusp, revealing a pulsed magnetopause reconnection. The consequent enhanced ionospheric flow events were imaged by the SuperDARN HF backscatter radars. The average convection patterns derived using the AMIE technique on data from the magnetometers, the EISCAT and SuperDARN radars, and the DMSP satellites show that the associated poleward-moving events also convected over the predicted footprint of the Cluster spacecraft. Cluster observed enhancements in the fluxes of both electrons and ions. These events were found to be essentially identical at all four spacecraft, indicating that they had a much larger spatial scale than the satellite separation of the order of 600 km. Some of the events show a correspondence between the lowest energy magnetosheath electrons detected by the PEACE instrument on Cluster 10–20 eV and the topside ionospheric enhancements seen by the ESR at 400–700 km. We suggest that a potential barrier at the magnetopause, which prevents the lowest energy electrons from entering the magnetosphere, is reduced when and where the boundary-normal magnetic field is enhanced and that the observed polar cap patches are produced by the consequent enhanced precipitation of the lowest energy electrons, making them and the low energy electron precipitation fossil remnants of the magnetopause reconnection rate pulses.

Autor: M. Lockwood - H. Opgenoorth - A. P. Van Eyken - A. Fazakerley - J.-M. Bosqued - W. Denig - J. A. Wild - C. Cully - R. Greenwald -



Documentos relacionados