Wave phenomena preceding and during a beam-plasma discharge

Journal Article · Tue Feb 28 23:00:00 EST 1989 · Journal of Geophysical Research; (USA)

DOI:https://doi.org/10.1029/JA094iA03p02654· OSTI ID:6048537

Boswell, R W; Morey, I J; Porteous, R K ^[1]

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1. Australian National Univ., Canberra, Australian Capital Territory (Australia)

The waves and associated phenomena which are generated prior to and during the beam-plasma discharge (BPD) in the waves on magnetized beams and turbulence (WOMBAT) apparatus are described. These range in frequency from below the ion gyrofrequency of a few kilohertz to strong harmonics of the electron plasma frequency above 1 GHz. The low-frequency ion waves appear to be driven by E {times} B forces arising from the nonneutrality of the electron beam-plasma column at low beam currents (I{sub b}) or low gas pressures (P). As I{sub b} increases, the motion becomes chaotic after a sequence of wave period doublings resulting in the generation of subharmonies. Windows of coherent motion are observed within the chaotic regions. Further increases in I{sub b} lead to increases in ionizing collisions and when the background plasma density becomes sufficiently high, waves around the electron plasma frequency can be generated. Initially, these waves are modulated by the gross density perturbations of the large-amplitude ion waves, but subsequently they also increase to large amplitudes: e{phi}/kT {approximately} 1. This is sufficient to accelerate the background electrons to ionizing energies and produce the BPD. At low pressures this occurs for f{sub pe}/f{sub ce} {approximately} 0.5 (BPD1) with the process occurring in short bursts ({approximately} 100{tau}{sub pe}). Increasing I{sub b} produces a sudden jump in the frequency to {approximately} 1.5 f{sub ce} and a further increase in the plasma density and luminosity, which the authors term BPD2.

• OSTI ID: 6048537
• Journal Information: Journal of Geophysical Research; (USA), Journal Name: Journal of Geophysical Research; (USA) Vol. 94:A3; 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
ACCELERATION
BEAM-PLASMA SYSTEMS
BEAMS
EARTH ATMOSPHERE
ELECTRON BEAMS
INSTABILITY
IONIZATION
IONOSPHERE
LANGMUIR FREQUENCY
LEPTON BEAMS
MODULATION
PARTICLE BEAMS
PLANETARY IONOSPHERES
PLASMA DENSITY
PLASMA INSTABILITY
PLASMA WAVES
WAVE PROPAGATION