University of Oulu

Poluianov, S., & Mishev, A. (2021, July 7). The altitude profile of the cosmic ray atmospheric cutoff. Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021). 37th International Cosmic Ray Conference. https://doi.org/10.22323/1.395.1331

The altitude profile of the cosmic ray atmospheric cutoff

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Author: Poluianov, Stepan1; Mishev, Alexander1
Organizations: 1University of Oulu, 90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.8 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2021081643323
Language: English
Published: Sissa, 2021
Publish Date: 2021-08-16
Description:

Abstract

Neutron monitors are the main ground-based instruments for continuous measurements the cosmic-ray intensity operating over more than five decades. Those instruments are energy-integrating detectors with count rates governed by the atmospheric and geomagnetic cutoffs. The geomagnetic cutoff dominates (up to 17 GV in rigidity) over most of the globe. However, it is negligible in the polar regions, and there, the atmospheric cutoff is important. The atmospheric cutoff depends on the elevation of the instrument above sea level (on the atmospheric depth), and it is estimated as ~1 GV for cosmic-ray protons at sea level. However, the cutoff is not precisely known at higher altitudes. This is specifically important for studies based on high-altitude polar neutron monitors, which count rate is solely defined by the atmospheric cutoff.

We present a newly estimated altitude profile of the atmospheric cutoff for cosmic-ray protons, which can be used in analysis of both galactic cosmic rays and solar energetic particles. We computed the profile using two methods. The first one is based on Monte Carlo simulation of the cosmic-ray induced cascade in the atmosphere with the PLANETOCOSMICS code. The second one uses recently computed and verified neutron monitor yield function by Mishev et al., 2020, which considers the efficiency of the instrument. Both methods agree reasonably well, though the yield-function based one provides a more conservative result, as expected. There are two definitions of solar-particle sub-GLE (sub-Ground-Level-Enhancement) events by Raukunen et al. (2018) and Poluianov et al. (2018) based on different principles. Considering the derived in this study atmospheric cutoff at altitudes about 3000 m a.s.l., we conclude: there is no contradiction between the definitions.

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Series: POS. Proceedings of science
ISSN: 1824-8039
ISSN-E: 1824-8039
ISSN-L: 1824-8039
Volume: 395
Article number: 1331
DOI: 10.22323/1.395.1331
OADOI: https://oadoi.org/10.22323/1.395.1331
Host publication: Proceedings of 37th International Cosmic Ray Conference (ICRC2021)
Conference: International Cosmic Ray Conference
Type of Publication: B3 Article in conference proceedings
Field of Science: 115 Astronomy and space science
Subjects:
Funding: We acknowledge the support from the Academy of Finland (projects 330064 QUASARE and 321882 ESPERA).
Academy of Finland Grant Number: 330064
321882
Detailed Information: 330064 (Academy of Finland Funding decision)
321882 (Academy of Finland Funding decision)
Copyright information: © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).
  https://creativecommons.org/licenses/by-nc-nd/4.0/