Electric fields and cold electrons in the vicinity of comet Halley

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

DOI:https://doi.org/10.1029/90JA02459· OSTI ID:5192641

Laakso, H ^[1]

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1. Finnish Meteorological Institute, Helsinki (Finland) European Space Agency, Noordwijk (Netherlands)

The structure and dynamics of the plasma environment on the sunward side of comet Halley are investigated using measurements during the Vega inbound encounters from a double probe antenna and two Langmuir probes (the APV-V experiment), within a cometocentric distance of {approximately}850,000 km. Based upon the behavior of the electric fields and the cold electrons, three regions can be identified in the cometosheath (in particular during the Vega 1 approach): transition layers are passed through at {approximately}780,000 km (R{sub 1}) and {approximately}360,000 km (R{sub 2}). The outer cometosheath (near and beyond R{sub 1}) is characterized by large-scale variations in the cold electron density and the electric field, peaking at {approximately}1 mHz. The R{sub 2} crossing is detected in the plasma wave data as enhanced fluctuations at {approximately}15 mHz. About 25,000 km downstream of R{sub 2}, the spacecraft traverses a current layer (thickness {approximately}10,000 km) indicated by a sharp gradient in the dc electric field and the cold electron density. The continuous, relatively rapid increase in the intensity of plasma waves begins at a cometocentric distance of {approximately}200,000 km. Simultaneously, the cold electron density starts growing in accordance with the r{sup {minus}2} law. The cometopause crossing at {approximately}160,000 km produces only moderate effects in the APV-V measurements. In the cometary plasma region, some interesting features are examined, such as a current layer passed by Vega 1 at 54,000 km and sudden ion density enhancements observed by Vega 2 at {approximately}35,000 km. On several occasions, the APV-V measurements are heavily influenced by dust particles striking the spacecraft structure. From these events the author concludes that the sudt particles are strongly charged and partially coupled to cometary plasmas (or vice versa).

• OSTI ID: 5192641
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A5; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGED PARTICLES
COMETS
COSMIC DUST
DUSTS
DYNAMICS
ELECTRIC FIELDS
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
ELEMENTARY PARTICLES
ENVIRONMENT
FERMIONS
HALLEY COMET
INTERACTIONS
IONS
LEPTONS
MATHEMATICAL MODELS
MECHANICS
MORPHOLOGY
PLASMA
PLASMA DIAGNOSTICS
PLASMA WAVES
SOLAR ACTIVITY
SOLAR WIND
SPACE VEHICLES
VARIATIONS
VEGA SPACE PROBES
VEHICLES