Complex Analysis of the Polar Substorm Based on Magnetic, Optical, and Radar Observations near Spitsbergen
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A comprehensive analysis of the polar substorm registered by IMAGE network stations close to the poleward boundary of the auroral oval has been carried out with THEMIS, CLUSTER, and GEOTAIL satellites in favorable positions for analysis. The observation interval is characterized by a low level of geomagnetic activity. The polar substorm looked like three negative, bay-like disturbances and developed within an ordinary substorm registered at stations in the middle of the auroral zone half an hour before the polar substorm. Each bay-like disturbance of the polar substorm was accompanied by a poleward drift of aurora and westward electrojet, a Pi2 pulsation group, a surge of magnetic activity over the range of 0.1–10 Hz, and enhancement of electronic precipitations over Spitsbergen. The differences between the first activation and two subsequent ones in the aurora dynamics, ionospheric convection, and electronic precipitations are revealed. The disturbed zone longitudinal sizes and position in the magnetosphere are estimated. Possible causes of the substorm onset and disturbances associated with it are discussed. The results of the study expand the statistics on the polar substorm phenomenon and will enable insight into its nature.
Geomagnetic activity indices Dst and Kp are taken from the Kyoto University database. The authors are grateful to John Hopkins University (JHU/APL) and to the OVATION project for opportunities to explore the auroral oval parameters, to FGM team and ESA Cluster archive for magnetic data from CLUSTER satellites. EISCAT is an international association financed by the research organizations of China (CRIRP), Finland (SA), Japan (NIPR and STEL), Norway (NFR), Sweden (VR), and England (NERC). Data from the IMAGE network magnetometers, keograms from LYR and ABK cameras, and the online procedure of calculation of equivalent ionospheric currents are available on the website of the MIRACLE project. Data from GEOTAIL and THEMIS satellites are taken from the CDAWeb database. The authors are grateful to N. Safargaleeva (Polar Geophysical Institute) for assistance in the data selection process.
VS acknowledges support from the Academy of Finland via grant 316991.
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