Barium swarm: An ionospheric alternating current generator in CRIT I

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA01974· OSTI ID:5187060

Brenning, N ^[1]; Kelley, M C; Swenson, C ^[2]; Providakes, J ^[3]; Stenbaek-Nielsen, H C ^[4]

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1. Royal Inst. of Tech., Stockholm (Sweden)
2. Cornell Univ., Ithaca, NY (USA)
3. MITRE Corp., Bedford, MA (USA)
4. Univ. of Alaska, Fairbanks (USA)

A model is developed for the motion of a low-{beta} cloud of plasma which starts with uniform velocity V{sub i} across the magnetic field through a larger ambient plasma. The model cloud is a circular cylinder of length L, with the axis aligned with the magnetic field. The density limit above which the cloud is self-polarized to E{sub p} = {minus}V{sub i}xB is determined. At lower cloud densities the internal electric field is tilted at an angle between antiparallel to the injection direction V{sub i} and the self-polarization direction E{sub p} = {minus}V{sub i}xB and becomes close to antiparallel to V{sub i} for thin clouds. The ions in thin clouds perform a collective gyration with decreasing amplitude, which a stationary observer will see as an oscillation involving electric, magnetic, and density perturbations with a frequency close to the ion gyro frequency. The currents perpendicular to B inside the cloud are a combination of electron Hall current, ion current, and plasma displacement current. They combine as magnetic-field-aligned currents which are drawn from the ambient ionosphere by a divergence in the perpendicular electric field. These field-aligned currents give a perturbation of the magnetic field which is related to the electric field perturbation by {Delta}E/{Delta}B {approx} V{sub A}. The low-density version of the model is applied to an oscillation observed by a subpayload in the ionospheric rocket experiment CRIT I, which had a frequency close to the barium gyrofrequency, electric field fluctuations of amplitude 10 mV/m, density fluctuations with {Delta}n/n {approx} 0.2, and a time duration of 1 s. All four features can be reproduced by the model, using a density and an injection velocity consistent with other independent observations from CRIT I. In CRIT I the magnetic oscillations were not measured at the subpayload, and the relation {Delta}E/{Delta}B {approx} V{sub A} could not be tested.

• OSTI ID: 5187060
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A6; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGED PARTICLES
CURRENTS
DIAGNOSTIC TECHNIQUES
EARTH ATMOSPHERE
ELECTRIC CURRENTS
ELECTRIC FIELDS
IONIZATION
IONOSPHERE
IONS
MATHEMATICAL MODELS
PLANETARY IONOSPHERES
PLASMA DENSITY
PLASMA DRIFT
ROCKETS
VELOCITY