Velocity distributions of cometary protons picked up by the solar wind

Journal Article · Mon May 01 04:00:00 EDT 1989 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA094iA05p05227· OSTI ID:6069280

Neugebauer, M; Lazarus, A J; Balsiger, H; Fuselier, S A; Neubauer, F M; Rosenbauer, H

Velocity space distributions of picked up cometary protons were measured by the ion mass spectrometer on the Giotto spacecraft upstream of the Halley bow shock. Large pitch angle anisotropies were observed at all distances >1.2 x 10/sup 6/ km from the comet. As expected, pitch angle diffusion was much more rapid than energy diffusion. When the field was quasi-parallel to the solar wind velocity vector, it was possible to discern the effect of pitch angles scattering by sunward propagating, field-aligned hydromagnetic waves, but there is evidence for other scattering modes as well. For quasi-perpendicular geometries, the pitch angle distribution was very asymmetric with phase space density peaks near pitch angles of 180/sup 0/. It is suggested that the asymmetric pitch angle distribution may be caused by global rather than local wave-particle interactions. Just outside the shock, the pitch angle distribution was nearly isotropic and the radius of the pickup shell increased significantly. copyright American Geophysical Union 1989

• Research Organization: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
• OSTI ID: 6069280
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 94:A5; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANGULAR VELOCITY
COMETS
ENERGY RANGE
EV RANGE
EV RANGE 10-100
EV RANGE 100-1000
HALLEY COMET
HYDROMAGNETIC WAVES
MASS SPECTROMETERS
MEASURING INSTRUMENTS
PROTON SPECTRA
SHOCK WAVES
SOLAR ACTIVITY
SOLAR WIND
SPECTRA
SPECTROMETERS
VELOCITY
WAVE PROPAGATION