The relationship between substorm onset and fast flow generation in Earth's magnetotail
Abstract
We use global resistive MHD simulations to investigate the relationship between the onset of magnetic reconnection and the generation of fast flows in the near-Earth magnetotail. We find that a southward turning of the IMF after a prolonged period of northward IMF results in the formation of a thin current sheet and the onset of reconnection in the dipole transition region (about 10-12 RE). We identify the formation of the new near-Eath X line as substorm onset. The change in magnetic topology results in the tailward ejection of a large (~5 RE) plasmoid. If the IMF remains southward, the aspect ratio of the tail current sheet increases on a time scale of a few minutes until the tail X line reaches ~25 RE, after which the current sheet becomes unstable to secondary plasmoid formation. Earthward propagating plasmoids are identified as dipolarization fronts and fast flow channels that break in the dipole transition region. These results suggest that: 1) near-Earth tail reconnection should occur closer to Earth than previously thought; and 2) that the onset of fast magnetotail flows further down the tail occurs after substorm onset closer to Earth, when the tail current sheet aspect ratio reaches the critical plasmoid-unstable value. We discuss the crucial role of ion scale physics (namely, the Hall terms in the generalized Ohm's law) in the generation of the field-aligned currents that relate these magnetospheric phenomena to their auroral counterparts.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM13D3330D
- 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