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Magnetotail energy dissipation during an auroral substorm
E V Panov1, W Baumjohann1, R A Wolf2
1Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
Nature Physics
|December 6, 2016
Summary
Violent space plasma energy releases during substorms are modulated by field-aligned currents (FACs). These currents control auroral brightness and energy dissipation in the ionosphere, driven by plasma jet braking and oscillations.
Area of Science:
- Space Physics
- Plasma Physics
- Geophysics
Background:
- Substorms release significant space plasma energy from Earth's magnetotail, causing intense electric currents and bright auroras.
- The precise mechanisms modulating these currents and controlling energy dissipation in the ionosphere remain incompletely understood.
Purpose of the Study:
- To investigate the role of field-aligned currents (FACs) in modulating magnetotail energy release during substorms.
- To understand how plasma energy is dissipated in the ionosphere and how auroral displays are controlled.
Main Methods:
- Utilized data from the THEMIS satellite fleet, including imagers and magnetometers.
- Analyzed ground-based observations to correlate with satellite measurements.
Main Results:
- Identified field-aligned currents (FACs) as key modulators of plasma energy dissipation.
- Demonstrated that FACs are generated during magnetotail topology changes and the braking of plasma jets.
- Observed that auroral arc movement is linked to plasma oscillations and the expansion/restretching dynamics of the magnetotail.
Conclusions:
- Plasma energy dissipation during substorms is controlled by FACs, which are influenced by plasma pressure and flux tube volume gradients.
- The observed auroral dynamics, including equatorward movement of discrete arcs, are sufficient to dissipate the released energy.
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