University of Oulu

Asvestari, E., Gil, A., Kovaltsov, G. A., & Usoskin, I. G. (2017). Neutron monitors and cosmogenic isotopes as cosmic ray energy-integration detectors: Effective yield functions, effective energy, and its dependence on the local interstellar spectrum. Journal of Geophysical Research: Space Physics, 122, 9790–9802.

Neutron monitors and cosmogenic isotopes as cosmic ray energy-integration detectors : effective yield functions, effective energy, and its dependence on the local interstellar spectrum

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Author: Asvestari, Eleanna1,2; Gil, Agnieszka3; Kovaltsov, Gennady A.4;
Organizations: 1Space Climate Research Unit, University of Oulu, Oulu, Finland
2Department of Physics, University of Helsinki, Helsinki, Finland
3Institute of Mathematics and Physics, Siedlce University, Siedlce, Poland
4Ioffe Physical-Technical Institute, St. Petersburg, Russia
5Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.8 MB)
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Language: English
Published: American Geophysical Union, 2017
Publish Date: 2018-04-13


The method of assessment of galactic cosmic rays (GCR) variability over different timescales, using energy-integrating ground-based detectors such as a neutron monitor and cosmogenic isotopes ¹⁰Be and ¹⁴C stored in natural archives is revisited here. The effective yield functions for cosmogenic ¹⁴C (globally mixed in the atmosphere) and ¹⁰Be (realistically deposited in the polar region) are calculated and provided, in a tabulated form, in the supporting information. The effective energy of a detector is redefined so that the variability of the flux of GCR particles at this energy is equal to that of the detector’s count rate. The effective energy is found as 11–12 GeV/nucleon for the standard polar neutron monitor, and 6–7 GeV/nucleon and 5.5–6 GeV/nucleon for ¹⁴C and ¹⁰Be, respectively. New “calibration” relations between the force-field modulation potentials, based on different models of local interstellar spectra (LIS) are provided. While such relations are typically based on refitting the modeled cosmic ray spectra with a prescribed LIS model, the method introduced here straightforwardly accounts for the exact type of the detector used to assess the spectrum. The relations are given separately for ground-based neutron monitors and cosmogenic isotopes. This work allows for harmonization of different works related to variability of galactic cosmic ray flux in the vicinity of Earth, on long-term scale.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 122
Issue: 10
Pages: 9790 - 9802
DOI: 10.1002/2017JA024469
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This work was partially supported by the ReSoLVE Centre of Excellence (Academy of Finland, project 272157). A. G. acknowledges the Polish National Science Centre, decision DEC-2016/22/E/HS5/00406.
Academy of Finland Grant Number: 272157
Detailed Information: 272157 (Academy of Finland Funding decision)
Copyright information: ©2017. American Geophysical Union.