A multipoint study of a substorm occurring on 7 December, 1992, and its theoretical implications

• Main Authors: Fox, N. J., Cowley, S. W. H., Davda, V. N., Enno, G., Friis-Christensen, E., Greenwald, R. A., Hairston, M. R., Lester, M., Lockwood, M., Lühr, H., Milling, D. K., Murphree, J. S., Pinnock, M., Reeves, G. D.
• Other Authors: GSFC Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center (GSFC), Physics Department, STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Department of Physics and Astronomy Calgary, University of Calgary, Danish Space Research Institute (DSRI), Johns Hopkins University Applied Physics Laboratory Laurel, MD (APL), University of Texas at Dallas Richardson (UT Dallas), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Department of Physics, Okayama University, British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Los Alamos National Laboratory (LANL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1999
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Greenland; EISCAT
• Online Access: https://hal.science/hal-00316696; https://hal.science/hal-00316696/document; https://hal.science/hal-00316696/file/angeo-17-1369-1999.pdf

International audience On 7 December 1992, a moderate substorm was observed by a variety of satellites and ground-based instruments. Ionospheric flows were monitored near dusk by the Goose Bay HF radar and near midnight by the EISCAT radar. The observed flows are compared here with magnetometer observations by the IMAGE array in Scandinavia and the two Greenland chains, the auroral distribution observed by Freja and the substorm cycle observations by the SABRE radar, the SAMNET magnetometer array and LANL geosynchronous satellites. Data from Galileo Earth-encounter II are used to estimate the IMF B z component. The data presented show that the substorm onset electrojet at midnight was confined to closed field lines equatorward of the pre-existing convection reversal boundaries observed in the dusk and midnight regions. No evidence of substantial closure of open flux was detected following this substorm onset. Indeed the convection reversal boundary on the duskside continued to expand equatorward after onset due to the continued presence of strong southward IMF, such that growth and expansion phase features were simultaneously present. Clear indications of closure of open flux were not observed until a subsequent substorm intensification 25 min after the initial onset. After this time, the substorm auroral bulge in the nightside hours propagated well poleward of the pre-existing convection reversal boundary, and strong flow perturbations were observed by the Goose Bay radar, indicative of flows driven by reconnection in the tail.