Forbush decreases and particle acceleration in the outer heliosphere

Journal Article · Tue May 01 04:00:00 EDT 1990 · Geophysical Research Letters (American Geophysical Union); (USA)

DOI:https://doi.org/10.1029/GL017i006p00761· OSTI ID:6517732

Van Allen, J A ^[1]; Mihalov, J D ^[2]

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1. Univ. of Iowa, Iowa City (USA)
2. NASA/Ames Research Center, Moffett Field, CA (USA)

Major solar flare activity in 1989 has provided examples of the local acceleration of protons at 28 AU (Pioneer 11) and of the propagation of Forbush decreases in galactic cosmic ray intensity to a heliocentric radial distance of 47 AU (Pioneer 10). The combination of these and previous data at lesser distances shows (a) that Forbush decreases propagate with essentially constant magnitude to (at least) 47 AU and with similar magnitude at widely different ecliptic longitudes and (b) that the times for recovery from such decreases become progressively greater as the radial distance increases, being of the order of months in the outer heliosphere. A phenomenological scheme for (b) is proposed and fresh support is given to the hypothesis that the solar cycle modulation of the galactic cosmic ray intensity is attributable primarily to overlapping Forbush decreases which are more frequent and of greater magnitude near times of maximum solar activity than at times of lesser activity.

• OSTI ID: 6517732
• Journal Information: Geophysical Research Letters (American Geophysical Union); (USA), Journal Name: Geophysical Research Letters (American Geophysical Union); (USA) Vol. 17:6; ISSN GPRLA; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ATMOSPHERES
BARYONS
COSMIC RADIATION
DISTANCE
ELEMENTARY PARTICLES
FERMIONS
FORBUSH DECREASE
HADRONS
HELIOSPHERE
IONIZING RADIATIONS
MODULATION
NUCLEONS
PIONEER SPACE PROBES
PROTONS
RADIATIONS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR CYCLE
SOLAR FLARES
SOLAR PARTICLES
SOLAR PROTONS
SOLAR RADIATION
SPACE VEHICLES
STELLAR RADIATION
VARIATIONS
VEHICLES