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Buoy-based detection of low-energy cosmic-ray neutrons to monitor the influence of atmospheric, geomagnetic, and heliospheric effects
  • +6
  • Martin Schrön,
  • Daniel Rasche,
  • Jannis Weimar,
  • Markus Otto Köhli,
  • Konstantin Herbst,
  • Bertram Boehrer,
  • Lasse Hertle,
  • Simon Kögler,
  • Steffen Zacharias
Martin Schrön
Helmholtz Centre for Environmental Research GmbH - UFZ

Corresponding Author:[email protected]

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Daniel Rasche
GFZ German Research Centre for Geosciences
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Jannis Weimar
Physikalisches Institut, Heidelberg University
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Markus Otto Köhli
Heidelberg University
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Konstantin Herbst
Christian-Albrechts-Universität zu Kiel
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Bertram Boehrer
UFZ - Helmholtz Centre for Environmental Research
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Lasse Hertle
Helmholtz-Centre for Environmental Research - UFZ, Department for Monitoring and Exploration Technologies
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Simon Kögler
Helmholtz-Centre for Environmental Research - UFZ, Department for Monitoring and Exploration Technologies
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Steffen Zacharias
UFZ Helmholtz Centre for Environmental Research
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Abstract

Cosmic radiation on Earth responds to heliospheric, geomagnetic, atmospheric, and lithospheric changes. In order to use its signal for soil hydrological monitoring, the signal of thermal and epithermal neutron detectors needs to be corrected for external influencing factors. However, theories about the neutron response to soil water, air pressure, air humidity, and incoming cosmic radiation are still under debate. To challenge these theories, we isolated the neutron response from almost any terrestrial changes by operating bare and moderated neutron detectors in a buoy on a lake in Germany from July 15 to December 02, 2014. We found that the count rate over water has been better predicted by a recent theory compared to the traditional approach. We further found strong linear correlation parameters to air pressure and air humidity for epithermal neutrons, while thermal neutrons responded differently. Correction for incoming radiation proved to be necessary for both thermal and epithermal neutrons, for which we tested different neutron monitors and correction methods. Here, the conventional approach worked best with the Jungfraujoch monitor in Switzerland, while the approach from a recent study was able to adequately rescale data from more remote neutron monitors. However, no approach was able to sufficiently remove the signal from a major Forbush decrease event, to which thermal and epithermal neutrons showed a comparatively strong response. The buoy detector experiment provided a unique dataset for empirical testing of traditional and new theories on CRNS. It could serve as a local alternative to reference data from remote neutron monitors.