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NASA NTRS1985

Long-term modulation of cosmic rays during solar cycle 21

A preliminary result concerning the rigidity dependence of the longer-term solar cycle modulation is reported. The long-term modulation, using monthly mean intensities and referred to November 1977 as a normalizing level, appear to be in accordance with the exponent gamma = 1, provided only Brisbane and Hobart data are used. Darwin data do not conform to this pattern except perhaps during the early years of the cycle until about the end of 1980, since when the Darwin long-term intensity has been largely steady, apart from Forbush-type decreases and the as yet unidentified vector from the observed SI vector. The true SI vector of galactic origin can be obtained. The resultant vector has the amplitude of 0.031% and the phase of 2.3h. The present result seems to be consistent with those so far reported.

Fenton, A. G.↗

NASA NTRS1985

Cosmic rays 10Be biennal data and their relationship to aurorae and sunspots

The galactic cosmic ray (C.R.) variations which should give information on three dimensional aspects of the heliospheric magnetic fields and on the solar wind, which modulate their influx into the Solar System were studied. In order to decode the information from the C.R. series it is necessary to know the mechanisms through which the modulation is produced. It it clear that a balance of effects with sources at different heliospheric latitudes results in the modulated C.R. intensity. It is found that the modulation of 10Be in polar ice may be due to at least two main contributions: (1) negative and in phase with the Solar flare activity modulating the cosmic ray flux in Forbush-type decreases, and (2) positive in phase with the appearance of large wind streams situated at both polar coronal holes. It is found that the high heliolatitude activity is related to a stable periodicity of 11.1y whereas the low heliolatitude activity contributes to the wondering of the solar cycles.

Attolini, M. R.↗

NASA NTRS1987

Solar activity and heliosphere-wide cosmic ray modulation in mid-1982

A plausible candidate flare is identified for each of the four major Forbush-like decrease events that were observed in the outer heliosphere in mid-1982. The associations are as follows: (1) FD 1 at P10 - backside flare at W152 deg on June 3; (2) FD 1 at P11 - 2B flare at E25 deg on June 6; (3) FD2 at P11 - 3B flare at E36 deg on July 12; and (4) FD 2 at P10 - 1N limb flare at W100 deg on July 22. In each case, the identified flare was 35 deg or less in ecliptic longitude from the affected satellite. There is no compelling evidence from near-sun spacecraft observations that the shocks from any of the four identified flares encompassed both P10 and P11. A significant fraction of the major near-sun interplanetary disturbances during June and July of 1982 arose in the relatively narrow range of Carrington longitude from 275-320 deg.

Cliver, E. W.↗