https://doi.org/10.1140/epjp/s13360-024-05191-2
Regular Article
Empirical implications of location-dependent cosmic ray diurnal anisotropy on small-amplitude Forbush decreases
1
Department of Industrial Physics, Faculty of Science, Ebonyi State University, 480101, Abakaliki, Ebonyi State, Nigeria
2
Astrophysics and Astronomy Research Unit, Department of Physics and Astronomy, University of Nigeria, 410101, Nsukka, Enugu State, Nigeria
3
Department of Physics, University of Jinka, 4420, Jinka, Jinka State, Ethiopia
Received:
7
July
2023
Accepted:
16
April
2024
Published online:
9
May
2024
Forbush decreases (FDs) are one of the most spectacular phenomena in the time-intensity changes of cosmic ray (CR) flux. They play a crucial role in space-weather predictions. Their varieties and manifestations at different locations are frequently linked with solar ejections and the associated anisotropic particle fluxes. As a key variable in space-weather research, every part of the events including precursors, onset, FD minimum, main/recovery phase, and the attendant CR anisotropies has received considerable attention in the literature. Nevertheless, the focus has generally been on high-magnitude FDs (
). Investigation of small-amplitude FDs (
), which are also caused by similar space weather conditions that generate large events, remains an open field as it has yet to receive adequate attention. While there are several catalogs of high-magnitude FDs, for example, we are not aware of any catalogs of low-amplitude FDs besides the event list recently published by our team. The detailed and rigorous analysis performed in the current work shows that two naturally superposed CR signals—11-year solar cycle oscillations and CR diurnal anisotropy—could make manual cataloging of small FDs difficult. Using an extremely sensitive version of the recently developed automatic functional harmonic analysis, catalogs of small-amplitude FDs are created from thirty neutron monitors at different locations. The relationship between these events and the amplitude of the accompanying CR anisotropies at the respective locations is tested. The results show that the connection between the parameters varies significantly between different points on the Earth. Although there are some exceptions, high- and low-rigidity stations register stronger and weaker connections, respectively.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2024. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
