University of Oulu

Gil, A., Mishev, A., Poluianov, S., & Usoskin, I. (2022). Diurnal anisotropy of polar neutron monitors: Dome C looks poleward. Advances in Space Research, 70(9), 2618–2624.

Diurnal anisotropy of polar neutron monitors : Dome C looks poleward

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Author: Gil, Agnieszka1; Mishev, Alexander2; Poluianov, Stepan2;
Organizations: 1Siedlce University, Institute of Mathematics, Konarskiego 2, 08-110 Siedlce, Poland
2Space Physics and Astronomy Research Unit and Sodankyl\"a Geophysical Observatory, University of Oulu, FI-90014 Oulu, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link:
Language: English
Published: Elsevier, 2022
Publish Date: 2023-12-14


Galactic cosmic rays (GCR) exhibit a small local anisotropy observed as diurnal variability of ground-based neutron monitor (NM) count rates. Since the asymptotic directions of various NMs are different, their ability to observe the GCR diurnal variation also varies. Here we show that the Dome C (DOMC) NM is hardly sensitive to the diurnal variation, with its amplitude being 0.03%, in contrast to other polar NMs whose sensitivity to the diurnal variability ranges from 0.16 to 0.4%. We argue that this is related to the fact that DOMC NM has a narrow asymptotic-direction cone looking nearly to the South pole (geographic latitude above 75°). This makes the DOMC NM a unique detector being the only existing NM accepting cosmic-ray particles originating from the off-equatorial region. This is important for detailed studies of cosmic-ray transport in the vicinity of Earth, specifically for anisotropic solar energetic particle events.

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Series: Advances in space research
ISSN: 0273-1177
ISSN-E: 1879-1948
ISSN-L: 0273-1177
Volume: 70
Issue: 9
Pages: 2618 - 2624
DOI: 10.1016/j.asr.2021.12.010
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: A.G. acknowledges R. Modzelewska for constructive discussion. We are grateful to the PIs of Dome C, Oulu, Thule, South Pole, Apatity, and Tere Adelie neutron monitors. The NM count rates were obtained from: (Dome C and Oulu NMs) and NMDB database, (Thule, South Pole, Apatity, and Tere Adelie). We are grateful to the personnel of Concordia station hosting the DOMC/DOMB instrumentation. Operation of DOMC/DOMB NMs is possible thanks to the hospitality of the Italian polar program PNRA (via the LTCPAA PNRA 2015/AC3 and the BSRN PNRA OSS-06 projects) and the French Polar Institute IPEV, and logistical support by the Finnish Antarctic Research Program (FINNARP). This work was supported by the Academy of Finland (Projects Nos. 330064 QUASARE and 321882 ESPERA).
Academy of Finland Grant Number: 330064
Detailed Information: 330064 (Academy of Finland Funding decision)
321882 (Academy of Finland Funding decision)
Copyright information: © 2022. This manuscript version is made available under the CC-BY-NC-ND 4.0 license