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Burlaga et al. 1995
Burlaga, L.F., Ness, N.F. and McDonald, F.B. (1995). Magnetic fields and cosmic rays in the distant heliosphere at solar maximum: Voyager 2 observations near 32 AU during 1990. Journal of Geophysical Research 100: doi: 10.1029/95JA01557. issn: 0148-0227.

The intensity of >70 MeV cosmic ray protons observed during solar cycle 22 by Voyager 2 (V2) in the distant heliosphere reached a minimum in 1990, corresponding to the maximum of solar activity in mid-1989 (allowing for the propagation time of the solar wind from the sun to Voyager 2 near 32 AU). A step decrease in the cosmic ray intensity observed within the first ≈125 days of 1990 was caused by a global merged interaction region (GMIR), consisting of a cluster of large-amplitude magnetic field strength fluctuations, in which the field was predominantly stronger than average. The step decrease consists of four events in each of which the decrease in cosmic ray intensity is relatively large, and the recovery is either brief or absent. The relation between the cosmic ray intensity and the magnetic field strength observed near 32 AU during this period at the maximum of solar activity in 1989/1990 is similar to that which Voyager 2 observed near 11 AU in 1982/1983 following the maximum of solar activity in the previous solar cycle in 1980. The local changes in the cosmic ray intensity profile are related to the magnetic field strength. Near solar maximum the emission rate of ejecta, which contain magnetic fields that deviate significantly from the spiral direction, is a maximum. Nevertheless, the distribution of elevation angles of the magnetic field observed by Voyager 2 during 1990 is essentially the same as that observed during earlier parts of the solar cycle from 1986 through 1989, including solar minimum in 1986 and 1987. During 1990, the width of the distribution of elevation angles at ≈32 AU was the same as that observed at 1 AU. Sectors were observed, but no sector structure was presented during 1990, just as in 1988, 1989, and 1991. The distribution of daily averages of the magnetic field strength is lognormal for 0.05 nT<B<0.25 nT. However, there are more strong magnetic fields than the lognormal distribution predicts for 0.25 nT<B<0.4 nT, owing to the large MIRs. The large-scale fluctuations of the magnetic field strength have a multifractal structure in the low-frequency range from 2.7 days to at least 21.3 days that influences the cosmic ray intensity profile. ¿ American Geophysical Union 1995

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Abstract

Keywords
Interplanetary Physics, Cosmic rays, Interplanetary Physics, Interplanetary magnetic fields
Journal
Journal of Geophysical Research
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Publisher
American Geophysical Union
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