Combined energy and pitch angle diffusion of pickup ions at comet Halley

Journal Article · Mon Apr 01 00:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA02608· OSTI ID:5260681

Ye, Gang; Cravens, T E ^[1]

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1. Univ. of Kansas, Lawrence (USA)

It is well known that cometary pickup ions (e.g., H{sub 2}O{sup +}, OH{sup +}, O{sup +}, CO{sup +}, H{sup +}) initially form a ring-beam distribution in the solar wind reference frame, which is highly unstable to the growth of MHD waves (such as ion-cyclotron waves). The low-frequency magnetic fluctuations (or waves), which were observed upstream of comet Halley, cannot only pitch angle scatter the pickup ions so that the distribution becomes at least partially isotropized, but also stochastically accelerate the ions, resulting in the energetic ion populations observed in the vicinity of comet Halley. The authors have used numerical solutions of the quasi-linear diffusion equation to investigate the cometary ion pickup process at comet Halley. Both pitch angle and energy diffusion are taken into account. Many quasi-linear models of cometary pickup ions exist which involve one type of diffusion or the other but not both types at once. They find that the pitch angle scattering occurs faster than the energy diffusion, as expected. Moreover, the results demonstrate that the distribution of accelerated energetic ions is more isotropic than that of ions which have just been picked up. In fact, the ion distribution function on the initial pickup shell is quite anisotropic, even close to the comet Halley bow shock.

• OSTI ID: 5260681
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A4; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
HALLEY COMET
SOLAR WIND
IONS
DISTRIBUTION FUNCTIONS
INTERACTIONS
ACCELERATION
CARBON MONOXIDE
DIFFUSION
HYDROMAGNETIC WAVES
HYDROXYL RADICALS
ISOTROPY
MOLECULAR IONS
NUMERICAL SOLUTION
OXYGEN
PROTONS
QUASILINEAR PROBLEMS
SCATTERING
WATER
BARYONS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHARGED PARTICLES
COMETS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
FUNCTIONS
HADRONS
HYDROGEN COMPOUNDS
NONMETALS
NUCLEONS
OXIDES
OXYGEN COMPOUNDS
RADICALS
SOLAR ACTIVITY
640107* - Astrophysics & Cosmology- Planetary Phenomena