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Record Neutron Monitor Rates from Galactic Cosmic Rays 2010 SHINE Workshop Su Yeon Oh 1 , John Bieber 1 , Paul Evenson 1

Record Neutron Monitor Rates from Galactic Cosmic Rays 2010 SHINE Workshop Su Yeon Oh 1 , John Bieber 1 , Paul Evenson 1 , John Clem 1 , Yu Yi 2 (syoh@bartol.udel.edu) 1 Bartol Research Institute, Dept. of Physics & Astronomy, University of Delaware

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Record Neutron Monitor Rates from Galactic Cosmic Rays 2010 SHINE Workshop Su Yeon Oh 1 , John Bieber 1 , Paul Evenson 1

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  1. Record Neutron Monitor Rates from Galactic Cosmic Rays 2010 SHINE Workshop Su Yeon Oh1, John Bieber1, Paul Evenson1, John Clem1, Yu Yi2 (syoh@bartol.udel.edu) 1 Bartol Research Institute, Dept. of Physics & Astronomy, University of Delaware 2 Dept. of Astronomy & Space Science, Chungnam National University, Korea

  2. ABSTRACT The recent prolonged, deep minimum in solar activity suggests that modulated Galactic cosmic rays might have attained new space-age highs. However reported neutron monitor rates are ambiguous; some record new highs, and others do not. This work examines the record of eight long-running, high-latitude neutron monitors, four in the northern hemisphere (Apatity, Inuvik, Oulu, Thule) and four in the southern hemisphere (Keguelen, McMurdo, Sanae, Terre Adelie). Most stations display changes in sensitivity, which we characterize by a simple linear trend. After correcting for the change in sensitivity, a consistent picture emerges: All stations considered display new highs at the recent solar minimum, approximately 3% above the previous record high. This work was supported by the BAERI Nuclear R & D Program of MEST/KOSEF, NSF grant OPP-0739620, and by NASA EPSCoR grant NNX09AB05A.

  3. BACKGROUND NASA SCIENCE NEWS on Sept. 29, 2009:Cosmic Rays Hit Space Age High According to sensors on NASA's ACE (Advanced Composition Explorer) spacecraft, galactic cosmic rays have just hit a Space Age high. Energetic iron nuclei counted by the CRIS on NASA's ACE spacecraft reveal that cosmic ray levels have jumped 19% above the previous Space Age high.

  4. Neutron Monitors seem to disagree about whether there was a space age record.

  5. We created a reference data set by averaging 8 high-latitude neutron monitors. The reference suggests there was a new record About 3.2 % above the old record.

  6. Comparing individual neutron monitor with the reference reveals that many neutron monitors have long-term changes in sensitivity. [Examples] Currently we do not understand the source of these changes in sensitivity. They are mysteries.

  7. After detrending count rates, a consistent picture emerges.

  8. Conclusion: At the recent solar minimum, Galactic cosmic rays at neutron monitor energies reached a new space age high approximately 3 % above the previous high. This work was supported by the BAERI Nuclear R&D Program of MEST/KOSEF, NSF grant OPP-0739620, and by NASA EPSCoR grant NNX09AB05A.

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