Abstract
Quiet-time anisotropy data have been obtained by the HEOS-1 spacecraft between December 1968 and April 1970 using an 8-sector analysis of a Čerenkov telescope which has a threshold rigidity of about 1 GV for protons. Meridian and ecliptic plane scans were made. Data obtained at satellite altitudes greater than 20 Earth radii were selected and showed consistent evidence for a sunward radial streaming component of amplitude ~ 0.3% while the azimuthal component from the east showed an apparently significant variation from 0.6% at the start of the period to less than 0.2% at later times. Experimental effects are considered and eliminated as a spurious source of the anisotropy.
As there is no comparable radial streaming at neutron monitor rigidities this effect would appear to be largely confined to particles in the rigidity range 1 to 5 GV. Radial streaming of this amplitude is incompatible with the Urch-Gleeson numerical solutions of the Fokker-Planck transport equation under spherical symmetry. Also no significant correlation of the anisotropy with the interplanetary sector structure was found. A probable explanation lies in a symmetrical falling off-ecliptic gradient associated with the zones of maximum solar activity.
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NAS/NRC Resident Research Associate, Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.
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Dyer, C.S., Engel, A.R., Quenby, J.J. et al. Observation and explanation of a 0.3% sunward radial streaming of 1 to 5 GV cosmic radiation. Sol Phys 39, 243–259 (1974). https://doi.org/10.1007/BF00154985
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DOI: https://doi.org/10.1007/BF00154985