NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The velocity distributions of cometary protons picked up by the solar windVelocity 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 greater than 1.2 x 10 to the 6th 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 angle 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 deg. 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.
Document ID
19890051530
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Neugebauer, M.
(California Institute of Technology Jet Propulsion Laboratory, Pasadena, United States)
Lazarus, A. J.
(MIT Cambridge, MA, United States)
Balsiger, H.
(Bern, Universitaet Switzerland)
Fuselier, S. A.
(Lockheed Research Laboratories Palo Alto, CA, United States)
Neubauer, F. M.
(Koeln, Universitaet Cologne, Federal Republic of Germany, United States)
Date Acquired
August 14, 2013
Publication Date
May 1, 1989
Publication Information
Publication: Journal of Geophysical Research
Volume: 94
ISSN: 0148-0227
Subject Category
Astrophysics
Accession Number
89A38901
Funding Number(s)
CONTRACT_GRANT: JPL-957906
CONTRACT_GRANT: NGL-22-009-015
CONTRACT_GRANT: NASW-3729
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available