Journal article
The field-aligned flow approximation for electrons within layers possessing a normal mass flux: A corollary to the deHoffmann-Teller theorem
Journal of Geophysical Research; (United States), Vol.92:A12(A12), pp.13447-13455
12/01/1987
DOI: 10.1029/JA092iA12p13447
Abstract
This paper establishes that the deHoffmann-Teller frame electron bulk velocity V{sub e}{sup HT}(x) is nearly parallel to the magnetic field B(x) everywhere through those one-dimensional, time stationary layers which possess a normal mass flux, even though electric fields perpendicular to the magnetic field exist throughout such layers. Examples of layers of this class are the fast and slow shocks as well as rotational discontinuities. The explicitly calculated corrections to {cflx V}{sub e}{sup HT}(x) {approx equal} {cflx B}(x) are proportional to (1) the electron pressure anisotropy, (2) the electron inertia, and (3) the bulk resistivity. The near alignment of electron bulk velocity inside layers with a normal mass flux represents, for electrons only, a nearly complete extension of the 1950 deHoffmann-Teller theorem concerning the exact alignment of electron and ion flows with the magnetic field in both asymptotic regions outside such layers. This alignment would be perfect within such layers if the electrons were approximated as a massless, dissipationless, isotropic gas. Without such approximations this alignment is better in more oblique shocks of either type. This approximate symmetry provides a simple description of the causes of currents within the layers and an overview of the two-fluid mixing which is caused by passage through them. Finally, in testing with electric and magnetic field profiles for the existence of a deHoffmann-Teller frame at magnetopause crossings is generally superior to ion bulk velocity-magnetic field tests of tangential stress balance. Such tests can be performed whenever the scale lengths of the layer are much larger than the electron gyroradius, regardless of the size of the layer relative to the ion gyroradius.
Details
- Title: Subtitle
- The field-aligned flow approximation for electrons within layers possessing a normal mass flux: A corollary to the deHoffmann-Teller theorem
- Creators
- J.D Scudder - Goddard Space Flight Center
- Resource Type
- Journal article
- Publication Details
- Journal of Geophysical Research; (United States), Vol.92:A12(A12), pp.13447-13455
- DOI
- 10.1029/JA092iA12p13447
- ISSN
- 0148-0227
- eISSN
- 2156-2202
- Language
- English
- Date published
- 12/01/1987
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199774402771
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