Substorm activity precursors in the dayside magnetic perturbations |
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| Affiliation: | 1. Arctic and Antarctic Research Institute, St Petersburg 199397, Russia;2. Danish Meteorological Institute, Copenhagen, Denmark;1. Division of Dermatology, University of Alberta, Canada;2. Division of Rheumatology, University of Alberta, Edmonton, Canada;3. Division of Hematology, University of Calgary, Canada;4. Division of Rheumatology, University of Calgary, Canada;1. Istituto Nazionale di Astrofisica, Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, Rome, Italy;2. Serco for ESA, European Space Agency, ESRIN, Directorate of Earth Observation Programmes, Largo G. Galilei 1, Frascati, Italy |
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| Abstract: | Magnetic data from a meridional chain of stations in Greenland and AL-indices of magnetic activity have been used to study the relationship between magnetic perturbations in the dayside cleft region and substorm activity in the night-time auroral zone. The analysis of 14 substorms, isolated and prolonged, has shown that intensification of westward currents in the postnoon sector of the cleft precedes or accompanies substorm development in the night-time auroral zone. Westward currents appear in the northern cleft as substorm precursors even under the adverse influence of the IMF positive By component. These currents trend to extend in the prenoon sector. To explain the relationship between the cleft currents and auroral electrojet the connection between neutral layer currents and noon Birkeland currents is proposed. This connection can be realized by means of the source region acting just inside the daytime magnetopause owing to stationary reconnection of geomagnetic field and IMF, the source region flowing downstream to the tail magnetopause. |
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