Propagation of a large Forbush decrease in cosmic‐ray intensity past the Earth, Pioneer 11 at 34 AU, and Pioneer 10 at 53 AU
1992; American Geophysical Union; Volume: 19; Issue: 14 Linguagem: Inglês
10.1029/92gl01445
ISSN1944-8007
AutoresJ. A. Van Allen, R. W. Fillius,
Tópico(s)Atmospheric Ozone and Climate
ResumoDuring 1991, large and distinctive Forbush decreases in cosmic‐ray intensity were observed at Pioneer 11 at 34 AU on 21 August and at Pioneer 10 at 53 AU on 30 September. An apparently related shock passed Voyager 1 at 46 AU on 14 September. These three events are plausibly associated with each other and with a large Forbush decrease at the Earth on 12 June. The apparent radial speed of propagation was about 820 km s −1 , independent of radial distance; and the decrease of cosmic‐ray intensity was of similar magnitude (≈ 20 percent) at Earth, Pioneer 11, and Pioneer 10, i.e., over a radial range 1 to 53 AU and over a range of heliocentric ecliptic longitude at least as great as 173°. For over a month following passage of the interplanetary shock by Pioneer 11, detectable intensities of locally accelerated protons of E p ≈ 1 MeV were present. The causative solar flare for the entire family of apparently related events was identified with reasonable certainty as a 3B/ X 12.0 one in active region 6659 on 11 June at W17 N31. These new observations together with comparable ones reported previously provide the basis for a new quantitative model of the propagation of Forbush decreases in the outer heliosphere, described by RWF in a paper submitted to the Journal of Geophysical Research .
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