Nonlinear electron magnetohydrodynamics physics. II. Wave propagation and wave-wave interactions

Journal Article · Tue Apr 15 04:00:00 EDT 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2903067· OSTI ID:21120240

Urrutia, J M; Stenzel, R L; Strohmaier, K D ^[1]

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1. Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

The propagation of low-frequency whistler modes with wave magnetic field exceeding the ambient field is investigated experimentally. Such nonlinear waves are excited with magnetic loop antennas whose axial field is aligned with the background magnetic field and greatly exceeds its strength. The oscillatory antenna field excites propagating wave packets with field topologies alternating between whistler spheromaks and mirrors. The propagation speed of spheromaks is observed to decrease with amplitude while that of mirrors increases with amplitude. The field distribution varies with amplitude: Spheromaks contract axially while mirrors spread out compared to linear whistlers. Consequently, the peak magnetic field and current densities in spheromaks exceed that of mirrors. Wave-wave interactions of nonlinear whistler modes is also studied. Counterpropagating spheromaks collide inelastically and form a stationary field-reversed configuration. The radius of the toroidal current ring depends on current and can be larger than that of the loop antenna. A tilted field-reversed configuration precesses in the direction of the electron drift. The free magnetic energy is dissipated in the plasma volume and converted into electron heat.

• OSTI ID: 21120240
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 4 Vol. 15; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLITUDES
ANTENNAS
CURRENT DENSITY
ELECTRON DRIFT
ELECTRONS
FIELD-REVERSED THETA PINCH DEVICES
MAGNETIC FIELDS
MAGNETIC MIRRORS
MAGNETOHYDRODYNAMICS
MIRRORS
NONLINEAR PROBLEMS
PLASMA
PLASMA CONFINEMENT
SPHEROMAK DEVICES
WAVE PACKETS
WAVE PROPAGATION
WHISTLER INSTABILITY
WHISTLERS