On large-scale rotational motions and energetics of auroral shear layers

Journal Article · Sat Jun 01 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA00446· OSTI ID:5313635

Lotko, W; Shen, M M ^[1]

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1. Dartmouth Coll., Hanover, NH (USA)

The stability, dynamics and energetics of an auroral shear layer are considered in the framework of incompressible, one-fluid magnetohydrodynamics, under conditions where current flow through the system is limited by the finite Pedersen conductivity and an enhanced field-aligned resistivity. The model includes a magnetospheric region where currents resulting from polarization electric fields and viscous forces are important, an ionospheric substrate of uniform conductivity, and a force-free acceleration region, characterized by a linear current-voltage relation and located at an intermediate altitude between the magnetospheric viscous/polarization layer and the ionosphere. It is assumed that the Alfven wave transit time across the viscous/polarization layer is small compared with the eddy time. Neutral stability of the model system is determined for a class of one-dimensional equilibria in which a specified current distribution at the upper boundary of the viscous/polarization layer produces a potential structure with convergent, localized reversals in the transverse (E {times} B) electric field. The calculated neutral curves depend on three nondimensional parameters related to the intensity of the imposed field-aligned current, the shear layer scale size, and the ratio of resistive to viscous drag at equilibrium. Numerical simulations of unstable configurations show that (1) two-dimensional quasi-steady rotational states arise when the equilibrium is weakly unstable; (2) eddy shedding turbulent states can arise when the equilibrium is strongly unstable; and (3) the flow kinetic energy and energy input/dissipation rates in the model system are reduced as a consequence of the instability. Power spectral densities for the electric and magnetic fields are also evaluated along sample satellite cuts through the shear layer.

• OSTI ID: 5313635
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A6; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAL ZONES
SHEAR
ACCELERATION
ALFVEN WAVES
EARTH MAGNETOSPHERE
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRIC FIELDS
ELECTRODYNAMICS
ENERGY LOSSES
IONOSPHERE
LAYERS
MATHEMATICAL MODELS
MOTION
NUMERICAL ANALYSIS
STABILITY
CURRENTS
EARTH ATMOSPHERE
ELECTRICAL PROPERTIES
HYDROMAGNETIC WAVES
LOSSES
MATHEMATICS
PHYSICAL PROPERTIES
PLANETARY IONOSPHERES
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena