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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
A12102,
10 PP., 2007
doi:10.1029/2006JA011894
Long-term decline of South Pole neutron rates
Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, Delaware, USA
Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, Delaware, USA
Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA
Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, Delaware, USA
Scripps Institute of Oceanography, University of California, San Diego, La Jolla, California, USA
Institute for Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire, USA
Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, Delaware, USA
The count rate recorded by a neutron monitor at South Pole, Antarctica, displays a long-term decline over the 32-year span from 1965 to 1997. The neutron rate follows an 11-year cycle with maxima at times of low solar activity, but the 1997 peak rate was approximately 8% lower than the 1965 peak rate based on 27-d averages. This change is much larger than that recorded by any other neutron monitor. We suggest that the South Pole monitor, owing to its unique position at both high latitude and high altitude (2820 m), has enhanced sensitivity at ∼1–3 GV relative to a sea level monitor and may be responding to a change in the intensity of primary cosmic rays in this rigidity region. Measurements of cosmic rays made aboard stratospheric balloons and on the IMP-8 spacecraft support the possibility of a long-term change in cosmic ray intensity.
Received 2 June 2006; accepted 24 August 2007; published 27 December 2007.
Citation: (2007), Long-term decline of South Pole neutron rates, J. Geophys. Res., 112, A12102, doi:10.1029/2006JA011894.
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