The thermal catastrophe model of substorms
The resonant absorption of Alfven waves in the plasma sheet boundary layer (PSBL) provides a significant source of energy for the heating of plasma sheet particles. We show that the energy absorbed is a function of the central plasma sheet (CPS) temperature. The heating curve when coupled with convective transport yields an equation of state for the steady state plasma sheet whose solution has the form of a mathematical catastrophe. We have previously suggested that this catastrophe is associated with the abrupt increase of energy dissipation during the onset of the substorm expansion phase. In this paper our master equation is generalized to include convection velocity /ital V//sub x/ self-consistent with pressure anisotropy, and to retain the dynamics describing the transition across the thermal catastrophe. The dynamic terms allow evaluation of the time scale for the catastrophe to occur. The evolution of the plasma sheet through the growth phase to onset is traced in the quasi-static limit, assuming that the system passes slowly through a succession of equilibrium states described by the stationary limit of the master equation. The state variable for the plasma sheet is the temperature /ital T/; the control variables are the evolving lobe field /ital B//sub l/ and the incident power flux, represented by /ital W//similar to//ital b//sup 2/, where /ital b/ is the amplitude of the driving waves at the surface of the PSBL. Other parameters are reduced to initial conditions and then scale self-similarly with the evolving /ital B//sub l/. For a physically reasonable range of /ital W/, catastrophe occurs as /ital B//sub l/ increases above a critical value, and in a relatively narrow range of local time, nominally 2200/lt//ital LT//lt/2400. The power dissipated after onset by resonant absorption is of order 10/sup 9/ W//ital R//sup 2//sub /ital e//.
- Research Organization:
- Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa (US); Plasma Physics Division, Science Applications International Corporation, McLean, Virginia
- OSTI ID:
- 5961979
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 94:A6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
EARTH MAGNETOSPHERE
MAGNETIC STORMS
SOLAR WIND
ALFVEN WAVES
ANISOTROPY
BOUNDARY LAYERS
CONVECTION
ENERGY ABSORPTION
EQUATIONS OF STATE
MATHEMATICAL MODELS
PLASMA HEATING
PLASMA SHEET
PRESSURE EFFECTS
ABSORPTION
EARTH ATMOSPHERE
ENERGY TRANSFER
EQUATIONS
HEAT TRANSFER
HEATING
HYDROMAGNETIC WAVES
LAYERS
MASS TRANSFER
SOLAR ACTIVITY
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena