Explosive Nature of Auroral Formation During Substorm Expansion Phase
Abstract
Substorms result from the dynamical response of the M-I coupling system to external solar wind driving and to internal dynamics. During the growth phase, energy and momentum are transferred from the solar wind into the magnetosphere. The M-I coupling system is constantly driven by the solar wind. A decrease in momentum transfer from the solar wind due to, for example, an IMF northward turning, will cause force imbalance in the tail, producing a net earthward body force acting on the magnetotail, and start a preconditioning stage. This huge earthward force can cause a large scale earthward movement of the tail, producing dipolarizations.
We emphasize the physics of the generation of substorm auroral arcs which is the key to understanding the explosive nature of substorm aurora and the triggering mechanism of substorm onset. During the preconditioning stage, the formation of localized onset auroral arcs can redistribute perpendicular mechanical and magnetic stresses in auroral flux tubes, locally decoupling the magnetosphere from ionosphere drag. This will enhance the tail earthward shear flows and rapidly build up stronger parallel electric fields in the auroral acceleration region, leading to a sudden and violent tail energy release.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM13D3328S
- Keywords:
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- 2431 Ionosphere/magnetosphere interactions;
- IONOSPHERE;
- 2740 Magnetospheric configuration and dynamics;
- MAGNETOSPHERIC PHYSICS;
- 2756 Planetary magnetospheres;
- MAGNETOSPHERIC PHYSICS;
- 7524 Magnetic fields;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY