Effects of dissipation on rotational discontinuities

Journal Article · Sun May 01 04:00:00 EDT 1988 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA093iA05p03969· OSTI ID:5962420

Wu, C C ^[1]

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1. University of California, Los Angeles (United States)

The effects of dissipation on rotational discontinuities have been studied as an initial-value problem. Starting with a rotational discontinuity, the author applies resistivity and viscosity and follows the resulting evolution of the system by numerically integrating in time the viscous, resistive MHD equations. The results show that by including dissipation, a rotational discontinuity is unstable and will evolve to an MHD intermediate shock of the kind whose shock frame fluid velocities are subfast, super-Alfvenic, and superslow ahead, and subfast, sub-Alfvenic, and superslow behind the shock. (However, with small dissipation, the intermediate shock and the rotational discontinuity would be very close.) The results also show that there are a larger class of shocklike structures, which do not satisfy Rankine-Hugoniot relations, in the time-dependent dissipative MHD equations. The results also indicate that the corresponding Riemann problem is not well-posed. in addition, the admissibility of MHD equations is discussed. The conclusion is that all entropy satisfying shocks along the shock curve are physical. This differs from the conventional view that intermediate shocks are not allowed. This also differs from the admissibility criterion of Oleinik (1957) and Liu (1981). However, their criterion is valid for a strictly hyperbolic system, whereas the set of MHD equations is nonstrictly hyperbolic. Regarding the magnetospheric physics, the study suggests that instead of rotational discontinuities, intermediate shocks should exist at the magnetopause. Thus one has a different signature from that of a rotational discontinuity to compare with space observations.

• OSTI ID: 5962420
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 93:A5; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALFVEN WAVES
COMPARATIVE EVALUATIONS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ENERGY LOSSES
EQUATIONS
EVALUATION
FLUID MECHANICS
HYDRODYNAMICS
HYDROMAGNETIC WAVES
LOSSES
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MAGNETOPAUSE
MATHEMATICAL MODELS
MECHANICS
NUMERICAL SOLUTION
RANKINE-HUGONIOT EQUATIONS
SHOCK WAVES
TIME DEPENDENCE
VISCOSITY