12:30 PM - 12:45 PM
[PEM28-03] Energy budget of the plasma sheet during auroral substorms
Keywords:Substorm, plasma sheet, aurora, Magnetohydrodynamics
Using the global MHD simulation, it is found that magnetic energy release rate and thermal energy accumulation rate are balanced in the plasma sheet during the early expansion phase of the simulated substorm. Around the peak of the expansion phase, energy release rate in the plasma sheet does not meet the energy consumption rate in the ionosphere. External energy source from outside of the plasma sheet is needed to maintain the high auroral activity. The JxB force of the dipolarization does the work to increase the thermal energy inside. This is how the accumulated magnetic energy within a distance of 10 Re is converted into the thermal energy during the early expansion. The increase of the thermal energy is the source of enhanced Region-2 field-aligned current system. Region1 field-aligned current must be supplied from outside of the plasma sheet to maintain the high auroral activity in the ionosphere. The dynamo of Region1 is slow-mode expansion in the cusp-mantle region. The enhanced conductivity plays the essential role to introduce the large Region 1 field aligned current because the dynamo has the nature of voltage-generator.