Kinetic structure of rotational discontinuities: Implications for the magnetopause

Journal Article · Sat Jul 01 04:00:00 EDT 1995 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JA03034· OSTI ID:117674

Krauss-Varban, D; Karimabadi, H; Omidi, N ^[1]

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1. Univ. of California, San Diego, La Jolla, CA (United States)

Magnetic field rotations in the high ion beta magnetosheath that are part of the magnetopause structure are expected to have only a small normal component. We have studied the properties of rotational discontinuities (RDs) under these conditions, viewed as the limit of weak intermediate shocks (ISs), by performing hybrid simulations with a reflecting wall boundary condition (piston method). With this dynamic formation, the sense and size of rotation are not arbitrarily predetermined, but rather evolve from the given upstream (magnetosheath) and downstream (magnetospheric) boundary conditions, similar to what takes place at the magnetopause. This work focuses on several aspects: the observed minimum shear of RDs, their width, their internal signature, and their relation to ISs in isotropic plasmas. Our simulation results are in agreement with the minimum shear observations, that is, the RDs choose the sense of rotation that corresponds to the minimum angle between the upstream and downstream field vector. The RDs are stable, with a unique scale size. Typical gradient scale half widths are one to four ion inertial lengths with a total width up to ten times of that, in agreement with magnetopause observations. We develop a generalized fluid theory of RDs and discuss the characteristic internal signatures of the rotational layer, comparing the kinetic simulation results to predictions from the generalized fluid theory. The results show that ion inertia, anisotropic pressure, finite Larmor radius effects, nonzero ion heat flux, and reflected ions all contribute to the signatures of RDs on kinetic scales.

• Research Organization: National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center
• Sponsoring Organization: USDOE
• OSTI ID: 117674
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A7 Vol. 100; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
66 PHYSICS
COMPUTERIZED SIMULATION
FLUID MECHANICS
GEOPHYSICS
MAGNETOPAUSE
REACTION KINETICS