Diurnal variations of galactic cosmic rays as detected by polar neutron monitors
Gil, Agnieszka; Mishevc, Alexander; Poluianovc, Stepan; Usoskin, Ilya (2024-09-27)
Sissa Medialab
27.09.2024
Gil, A., Mishevc, A., Poluianovc, S., & Usoskin, I. (2023). Diurnal variations of galactic cosmic rays as detected by polar neutron monitors. Proceedings of 38th International Cosmic Ray Conference (ICRC2023). PoS Proceedings of science, 444, 1331. https://doi.org/10.22323/1.444.1331
https://creativecommons.org/licenses/by-nc-nd/4.0/
© 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/
© 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/
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:oulu-202410106249
https://urn.fi/URN:NBN:fi:oulu-202410106249
Tiivistelmä
Abstract
Galactic cosmic rays (GCRs) present a small local anisotropy visible as a diurnal variation in the count rates of the ground-based neutron monitors (NMs). NMs have varying capabilities in observing these fluctuations due to their different asymptotic directions that span a wide range of latitudes. Due to the Earth’ s rotation, they continuously scan the GCR flux producing the diurnal variation in the count rates. Our study reveals that Dome C (DOMC) is the only NM that does not observe this daily variability (the amplitude is <0.03%) in contrast to other polar NMs, whose diurnal variation amplitudes range from 0.16 to 0.4%. The reason for this is the narrow asymptotic cone of the DOMC NM, which is directed almost towards the polar direction with a geographic latitude of over 75 degrees. As a result, DOMC NM is uniquely positioned to receive cosmic rays from outside the equatorial plane, making it particularly useful for investigating 3D cosmic-ray transport in the Earth's vicinity, especially during anisotropic solar energetic particle events.
Galactic cosmic rays (GCRs) present a small local anisotropy visible as a diurnal variation in the count rates of the ground-based neutron monitors (NMs). NMs have varying capabilities in observing these fluctuations due to their different asymptotic directions that span a wide range of latitudes. Due to the Earth’ s rotation, they continuously scan the GCR flux producing the diurnal variation in the count rates. Our study reveals that Dome C (DOMC) is the only NM that does not observe this daily variability (the amplitude is <0.03%) in contrast to other polar NMs, whose diurnal variation amplitudes range from 0.16 to 0.4%. The reason for this is the narrow asymptotic cone of the DOMC NM, which is directed almost towards the polar direction with a geographic latitude of over 75 degrees. As a result, DOMC NM is uniquely positioned to receive cosmic rays from outside the equatorial plane, making it particularly useful for investigating 3D cosmic-ray transport in the Earth's vicinity, especially during anisotropic solar energetic particle events.
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