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Field-aligned current reconfiguration and magnetospheric response to an impulse in the interplanetary magnetic field BY component
Ist Teil von
Geophysical research letters, 2013-06, Vol.40 (11), p.2489-2494
Ort / Verlag
Washington: Blackwell Publishing Ltd
Erscheinungsjahr
2013
Quelle
Access via Wiley Online Library
Beschreibungen/Notizen
When the interplanetary magnetic field (IMF) is dawnward or duskward, magnetic merging between the IMF and the geomagnetic field occurs near the cusp on the dayside flanks of the magnetosphere. During these intervals, flow channels in the ionosphere with velocities in excess of 2 km/s have been observed, which can deposit large amounts of energy into the high‐latitude thermosphere. In this study, we analyze an interval on 5 April 2010 where there was a strong dawnward impulse in the IMF, followed by a gradual decay in IMF magnitude at constant clock angle. Data from the Sondrestrom incoherent scatter radar and the Defense Meteorological Satellite Program spacecraft were used to investigate ionospheric convection during this interval, and data from the Active Magnetospheric and Planetary Electrodynamics Response Experiment (AMPERE) were used to investigate the associated Field‐Aligned Current (FAC) system. Additionally, data from AMPERE were used to investigate the time response of the dawnside FAC pair. We find there is a delay of approximately 1.25 h between the arrival of the dawnward IMF impulse at the magnetopause and strength of the dawnward FAC pair, which is comparable to substorm growth and expansion time scales under southward IMF. Additionally, we find at the time of the peak FAC, there is evidence of a reconfiguring four‐sheet FAC system in the morning local time sector of the ionosphere. Additionally, we find an inverse correlation between the dawn FAC strength and both the solar wind Alfvénic Mach number and the SYM‐H index. No statistically significant correlation between the FAC strength and the solar wind dynamic pressure was found.
Key Points
An impulse in IMF By drives fast flows in the high latitude ionosphere
The peak dawn‐side FAC strength occurs 1.25 hours after the impulse
The FAC strength correlates well with solar wind MA and SYM‐H