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

Journal Article · Mon Apr 01 04:00:00 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), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A4; ISSN JGREA; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

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