Latitudinal and field-aligned cosmic ray gradients 2 to 5 AU Voyages 1 and 2 and IMP 8

Journal Article · Thu Dec 01 04:00:00 EST 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA088iA12p09889· OSTI ID:5094700

Roelof, E C; Decker, R B; Krimigis, S M

Latitudinal and field-aligned cosmic ray gradients have been measured separately by inter-normalization of the similar integral response (greater than approximately 30 MeV/nucleon) and high counting rates of approximately 60 counts per second of the anticoincidence detectors of the LECP experiment on Voyagers 1 and 2 and the CPME experiment on IMP 8. The unambiguous separation of latitudinal from field-aligned gradients in long-lived (greater than 10 days) cosmic ray structures is possible because during their Earth-Jupiter transits, the two Voyagers are never separated by more than a few degrees in latitude or longitude, or by more than 8% of the helioradius of either spacecraft, and because the Voyagers remain magnetically well-connected to Earth, which allows a direct estimate of field-aligned gradients. The IMF connection is estimated by using the solar wind velocities measured by the PLS experiment on Voyager 1. Latitudinal gradients of approximately 2 to 5%/deg are found in short-lived (10 to 30 days) structures, while they are approximately 1 to 2%/deg in structures recurring over several solar rotations. Radial gradients, except in the onsets of Forbush decreases, are commonly approximately 2%/AU, although there are rotations on which neither a radial nor a latitudinal gradient is measurable above 1%/AU or 1%/deg. Application of diffusion-convection theory to these gradients shows that if one assumes that diffusion dominates transport transverse to the magnetic field, one obtains an upper bound on the transverse mean free path for scattering lambda/sub perpendicular/ much less than 10/sup -3/ AU at 1 GeV/nucleon, which is inconsistent with values predicted by diffusion theory.

• Research Organization: The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20707
• OSTI ID: 5094700
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 88:A12; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RAY FLUX
COSMIC RAY PROPAGATION
DIFFUSION
FORBUSH DECREASE
GEOGRAPHICAL VARIATIONS
IMP SATELLITES
INTERPLANETARY MAGNETIC FIELDS
INTERPLANETARY SPACE
LATITUDE EFFECT
MAGNETIC FIELDS
RADIATION FLUX
SATELLITES
SPACE
SPACE VEHICLES
VARIATIONS
VEHICLES
VOYAGER SPACE PROBES