Pulsed currents carried by whistlers. II. Excitation by biased electrodes

Journal Article · Sun May 01 00:00:00 EDT 1994 · Physics of Plasmas; (United States)

DOI:https://doi.org/10.1063/1.870692· OSTI ID:6930646

Urrutia, J M; Stenzel, R L; Rousculp, C L ^[1]

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1. University of California, Los Angeles, California 90024-1547 (United States)

The transport of time-dependent current between electrodes in contact with a large laboratory magnetoplasma is examined experimentally. Single electrodes biased with respect to the chamber wall or pairs of electrically floating electrodes are used to produce pulsed currents ([omega][sub [ital ci]][much lt]2[pi]/[Delta][ital t][much lt][omega][sub [ital ce]]). The associated magnetic field vector, [bold B]([bold r],[ital t]), is measured in space and time, and the total current density is calculated from [bold J]([bold r],[ital t])=[del][times][bold B]([bold r],[ital t])/[mu][sub 0]. The current front is found to propagate at a characteristic wave speed, which does not depend on current amplitude or polarity. The transient current spreads across [bold B][sub 0] within a conical region, which depends on source geometry and plasma parameters. It is shown by Fourier transforming [bold B]([bold r],[ital t]) into [bold B]([bold k],[omega]) that the transient fields consist of a spectrum of oblique low-frequency whistler waves. In Fourier space, the inductive and space charge electric fields are calculated from Faraday's law and the assumption that [bold E][sub tot]=[bold E][sub ind]+[bold E][sub sc] along [bold B][sub 0] is negligible. Inverse transforming yields [bold E]([bold r],[ital t]). The transient wave fields ([bold B],[bold J],[bold E]) exhibit multiple induction effects and the formation of space charges. The results are relevant to pulsed Langmuir probes, beams, and antennas as well as moving steady-state magnetic/current sources such as particle collectors on spacecraft and magnetized asteroids (e.g., Gaspra).

• OSTI ID: 6930646
• Journal Information: Physics of Plasmas; (United States), Vol. 1:5; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
WHISTLERS
CURRENT DENSITY
ASTEROIDS
ELECTRODES
FARADAY LAWS
FOURIER ANALYSIS
LANGMUIR PROBE
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
TRANSIENTS
ELECTRIC PROBES
ELECTROMAGNETIC RADIATION
FLUID MECHANICS
HYDRODYNAMICS
MECHANICS
NOISE
PROBES
RADIATIONS
RADIO NOISE
RADIOWAVE RADIATION
700330* - Plasma Kinetics
Transport
& Impurities- (1992-)
700340 - Plasma Waves
Oscillations
& Instabilities- (1992-)