Field-aligned currents during the extreme solar minimum between the solar cycles 23 and 24
Abstract
The solar minimum between solar cycles 23 and 24 was unusually long and deep. The afternoon upward region-1 (R1) field-aligned current (FAC) response to this extreme solar minimum was examined and compared to that for the entire solar cycle 23. The responses on the dayside are different than those on the nightside. The field-aligned current density (J//) on the dayside, at 12 - 17 MLT appears to peak in the declining phase of the solar max, in 2003, when the solar wind speed peaks, whereas J// on the nightside, at 18 - 23 MLT, appears insensitive to the solar cycle. In the interval 1995 - 2010, J// at 15 - 17 MLT appears to reach the lowest value during the extreme solar minimum in 2009, when the solar wind speed also reaches the lowest value. The J// response is consistent with our previous study that shows that afternoon R1 at 12 - 17 MLT is located mostly on open field lines or at the boundary layer, where the current is driven by the velocity shear at magnetopause boundary. However, on the nightside, at 18 - 23 MLT, R1 is located mostly on the closed field lines where J// is not driven directly and immediately by the solar wind. The FAC latitudinal width (Λ), on the other hand, shows the opposite trend. The nightside Λ exhibits a solar cycle effect such that Λ is smaller at the solar minimum and smallest during the extreme solar minimum in 2009, consistent with a previous study. However, the dayside Λ exhibits little solar cycle effect. As a result, the FAC intensity exhibits a solar cycle variation at all local times and the FAC intensity is lower during the extreme solar minimum that that of the previous solar minimum.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMSM23A2230W
- Keywords:
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- 2721 MAGNETOSPHERIC PHYSICS Field-aligned currents and current systems;
- 2736 MAGNETOSPHERIC PHYSICS Magnetosphere/ionosphere interactions;
- 2431 IONOSPHERE Ionosphere/magnetosphere interactions;
- 2784 MAGNETOSPHERIC PHYSICS Solar wind/magnetosphere interactions