PoS - Proceedings of Science
Volume 444 - 38th International Cosmic Ray Conference (ICRC2023) - Solar & Heliospheric Physics (SH)
Study of modulation cycles of cosmic ray diurnal anisotropy variation using 22 years of GRAPES-3 muon data
M. Zuberi*, K.P. Arunbabu, S. Ahmad, M. Chakraborty, S.R. Dugad, S.K. Gupta, B. Hariharan, Y. Hayashi, P. Jagadeesan, A. Jain, P. Jain, S. Kawakami, H. Kojima, S. Mahapatra, P.K. Mohanty, Y. Muraki, P.K. Nayak, T. Nonaka, A. Oshima, D. Pattanaik, M. Rameez, K. Ramesh, L.V. Reddy, S. Shibata, P. Subramanian and F. Varsiet al. (click to show)
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Pre-published on: July 25, 2023
Published on: —
Abstract
The diurnal variations of the galactic cosmic rays (GCRs) measured by ground-based detectors
represent an anisotropic flow of GCR at 1 AU, also known as solar diurnal anisotropy (SDA).
The GRAPES-3 muon telescope (G3MT) has been recording high statistics of muons at a rate
of ∼50000 per second for the past two decades allowing us to probe the tiny variations in the
muon flux caused by solar phenomena. We have examined the 22 years (2000-2021) of G3MT
data using the Fourier series technique to obtain the daily SDA amplitude and phase. We observe
that the yearly averages of SDA amplitudes have a period of one sunspot cycle (11 years), which
strongly correlates with the interplanetary magnetic field. The annual phase variation suggests
the presence of 22-year periodicity and shows a clear shift towards earlier hours with a decrease
in solar activity.
DOI: https://doi.org/10.22323/1.444.1349
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