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Cane et al. 1994
Cane, H.V., Richardson, I.G., von Rosenvinge, T.T. and Wibberenz, G. (1994). Cosmic ray decreases and shock structure: A multispacecraft study. Journal of Geophysical Research 99: doi: 10.1029/94JA01529. issn: 0148-0227.

We examine >60-MeV/amu ion data from three spacecraft (IMP 8 and Helios 1 and 2) at the time of a number of short term (1 GeV) detected by ground-based neutron monitors in the years 1976 to 1979. The multispacecraft data allow us to investigate the structure of the modulation region and in particular the relative importance, as a function of location, of the shock and shock driver (ejecta) in causing the reduction in particle densities. Although the shocks contributing to cosmic ray decreases often have particle enhancements associated with them in the >60-MeV/amu data, this is not the case for three of the events discussed in this paper where a shock-associated decrease is also evident. Whereas the shock can cause an increase or decrease at low (i.e., less than neutron monitor) energies, the reduction of particle densities in the driver, if it is intercepted, is usually evident at all energies. Thus the overall shape of a decrease at >60 MeV/amu depends primarily on whether the ejecta is intercepted. We find that the particle density inside ejecta increases with increasing radial distance from the Sun. In many of the events in this study, entry and exit of ejecta are accompanied by abrupt changes in the decrease and recovery rates which indicate that the effect of the ejecta is local. In constrast, the effect of the shock lasts many days after the shock has passed by and is evident at large angular distances from the longitude of the solar source, i.e., the effect of the shock is nonlocal. Within 1 AU there seems to be no radial dependence of the shock effect. One cosmic ray decrease seen at Earth, which had an unusual profile, can be understood if the median plane of the ejecta was inclined to the ecliptic. ¿ American Geophysical Union 1994

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Abstract

Keywords
Interplanetary Physics, Cosmic rays, Interplanetary Physics, Flare and stream dynamics, Interplanetary Physics, Interplanetary magnetic fields, Interplanetary Physics, Interplanetary shocks
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
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