Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity

Ambika Singh

doi:doi:10.11648/j.ijass.20261401.12

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Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity

Ambika Singh^*

Published in International Journal of Astrophysics and Space Science (Volume 14, Issue 1)

Received: 2 January 2026 Accepted: 14 January 2026 Published: 30 January 2026

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Abstract

The diurnal anisotropy of galactic cosmic ray intensity provides an important diagnostic of solar modulation processes operating in the heliosphere. In the present work, a comprehensive long-term investigation of the diurnal anisotropy has been carried out using pressure-corrected hourly neutron monitor data from two high-latitude stations, Moscow and Kiel, covering a period of 52 years (1965–2016) corresponding to solar cycles 20 to 24. Daily values of the first harmonic diurnal amplitude and phase were obtained through harmonic analysis, from which annual mean values were derived. The long-term relationship between the diurnal amplitude and phase has been examined on annual, solar-cycle, and solar magnetic polarity bases. While day-to-day variations of amplitude and phase are found to be statistically independent, their annual averages exhibit clear solar-cycle-dependent behavior. A weak positive correlation between the diurnal amplitude and phase is observed when all years are considered together. However, a pronounced odd–even solar cycle asymmetry emerges when the data are segregated into odd and even cycles. Strong and statistically significant positive correlations characterize the odd solar cycles, whereas even solar cycles display weak and insignificant correlations. Furthermore, a clear dependence on solar magnetic polarity is observed, with large positive correlations during positive polarity epochs (A > 0) and reduced or reversed correlations during negative polarity epochs (A < 0). These results provide strong observational evidence that long-term variations of cosmic ray diurnal anisotropy are governed not only by solar activity but also by heliospheric magnetic polarity and particle drift effects.

Published in	International Journal of Astrophysics and Space Science (Volume 14, Issue 1)
DOI	10.11648/j.ijass.20261401.12
Page(s)	14-19
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Galactic Cosmic Rays, Diurnal Anisotropy, Solar Cycle, Solar Magnetic Polarity, Neutron Monitor Observations

References

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[2]	Ananth, A. G., Venkatesan, D. and Pillai, S.; “Long-term changes in the cosmic ray diurnal anisotropy”, Solar Physics, 143, 187-196 (1993).
[3]	Ahluwalia, H. S. and Riker, J. F.; “Diurnal anisotropy during solar activity cycle twenty and diffusion-convection model”, Proc. 19th Int. Cosmic Ray Conf., San Diego (USA), 5, 116-119 (1985).
[4]	Axford, W. I.; “The modulation of galactic cosmic rays in the interplanetary medium”, Planet. Space Sci., 13, 115 (1965).
[5]	Forman, M. A. and Gleeson, L. J.; “Cosmic ray streaming and anisotropies” Astrophys. Space Sci., 32, 77-94 (1975).
[6]	Parker, E. N.; “Theory of streaming of cosmic rays and the diurnal variation”, Planet. Space Sci., 12, 735-749 (1964).
[7]	Hall, D. L., Duldig, M. L. and Humble, J. E.; “Analysis of sidereal and solar anisotropies in cosmic rays”, Space Sc. Rev., 78, 401-442 (1996).
[8]	Mori, S.; “Annual modulation of solar diurnal variation of the cosmic ray nucleonic component in three-dimensional space”, J. Geomag. Geoelectr., 27, 1-23(1975).
[9]	Munakata, K. and Nagashima, K.; “A theory of cosmic ray anisotropies of solar origin”, Plant. Space Sci., 34, 99 (1986).
[10]	Nagashima, K., Duggal, S. P. and Pomerantz, M. A.; “Cosmic ray anisotropy in three-dimensional space”, Planet. Space Sci., 16, 29-46 (1968).
[11]	Singh, Ambika, Tiwari, A. K. and Agrawal, S. P.; “Study of High and Low Amplitude Wave Trains of Cosmic Ray Diurnal Variation during Solar Cycle 23’’, J. Astrophys. Astr. 31, 89-96 (2010).
[12]	Singh, Ambika, Dubey, Divya, Singh, R. P. Tiwari, A. K.; ‘Variation of Upper Cut-off Rigidity of Cosmic Ray Diurnal Anisotropy”, IJIRSET, 2, 4648-4654 (2013).
[13]	Singh, Munendra, Badruddin; “Study of the cosmic ray diurnal anisotropy during different solar magnetic conditions”, Solar Physics, 233, 291-317 (2006).
[14]	Tiwari, A. K., Singh, Ambika and Agrawal, S. P.; “Study of the Diurnal Variation of Cosmic Rays during Different Phases of Solar Activity”, Solar Phys, 279, 253-267 (2012).
[15]	Venkatesan, D. and Badruddin; “Cosmic ray intensity variations in the 3-dimentional heliosphere”, Space Sci. Rev., 52, 121-194 (1990).
[16]	Yadav, R. S. and Badruddin ; “Solar longitudinal distribution of solar flares in association with Forbush decreases”, Ind. J. Radio Space phys., 12, 10 (1983).

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APA Style

Singh, A. (2026). Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity. International Journal of Astrophysics and Space Science, 14(1), 14-19. https://doi.org/10.11648/j.ijass.20261401.12

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ACS Style

Singh, A. Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity. Int. J. Astrophys. Space Sci. 2026, 14(1), 14-19. doi: 10.11648/j.ijass.20261401.12

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AMA Style

Singh A. Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity. Int J Astrophys Space Sci. 2026;14(1):14-19. doi: 10.11648/j.ijass.20261401.12

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@article{10.11648/j.ijass.20261401.12,
  author = {Ambika Singh},
  title = {Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity},
  journal = {International Journal of Astrophysics and Space Science},
  volume = {14},
  number = {1},
  pages = {14-19},
  doi = {10.11648/j.ijass.20261401.12},
  url = {https://doi.org/10.11648/j.ijass.20261401.12},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijass.20261401.12},
  abstract = {The diurnal anisotropy of galactic cosmic ray intensity provides an important diagnostic of solar modulation processes operating in the heliosphere. In the present work, a comprehensive long-term investigation of the diurnal anisotropy has been carried out using pressure-corrected hourly neutron monitor data from two high-latitude stations, Moscow and Kiel, covering a period of 52 years (1965–2016) corresponding to solar cycles 20 to 24. Daily values of the first harmonic diurnal amplitude and phase were obtained through harmonic analysis, from which annual mean values were derived. The long-term relationship between the diurnal amplitude and phase has been examined on annual, solar-cycle, and solar magnetic polarity bases. While day-to-day variations of amplitude and phase are found to be statistically independent, their annual averages exhibit clear solar-cycle-dependent behavior. A weak positive correlation between the diurnal amplitude and phase is observed when all years are considered together. However, a pronounced odd–even solar cycle asymmetry emerges when the data are segregated into odd and even cycles. Strong and statistically significant positive correlations characterize the odd solar cycles, whereas even solar cycles display weak and insignificant correlations. Furthermore, a clear dependence on solar magnetic polarity is observed, with large positive correlations during positive polarity epochs (A > 0) and reduced or reversed correlations during negative polarity epochs (A < 0). These results provide strong observational evidence that long-term variations of cosmic ray diurnal anisotropy are governed not only by solar activity but also by heliospheric magnetic polarity and particle drift effects.},
 year = {2026}
}

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TY  - JOUR
T1  - Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity
AU  - Ambika Singh
Y1  - 2026/01/30
PY  - 2026
N1  - https://doi.org/10.11648/j.ijass.20261401.12
DO  - 10.11648/j.ijass.20261401.12
T2  - International Journal of Astrophysics and Space Science
JF  - International Journal of Astrophysics and Space Science
JO  - International Journal of Astrophysics and Space Science
SP  - 14
EP  - 19
PB  - Science Publishing Group
SN  - 2376-7022
UR  - https://doi.org/10.11648/j.ijass.20261401.12
AB  - The diurnal anisotropy of galactic cosmic ray intensity provides an important diagnostic of solar modulation processes operating in the heliosphere. In the present work, a comprehensive long-term investigation of the diurnal anisotropy has been carried out using pressure-corrected hourly neutron monitor data from two high-latitude stations, Moscow and Kiel, covering a period of 52 years (1965–2016) corresponding to solar cycles 20 to 24. Daily values of the first harmonic diurnal amplitude and phase were obtained through harmonic analysis, from which annual mean values were derived. The long-term relationship between the diurnal amplitude and phase has been examined on annual, solar-cycle, and solar magnetic polarity bases. While day-to-day variations of amplitude and phase are found to be statistically independent, their annual averages exhibit clear solar-cycle-dependent behavior. A weak positive correlation between the diurnal amplitude and phase is observed when all years are considered together. However, a pronounced odd–even solar cycle asymmetry emerges when the data are segregated into odd and even cycles. Strong and statistically significant positive correlations characterize the odd solar cycles, whereas even solar cycles display weak and insignificant correlations. Furthermore, a clear dependence on solar magnetic polarity is observed, with large positive correlations during positive polarity epochs (A > 0) and reduced or reversed correlations during negative polarity epochs (A < 0). These results provide strong observational evidence that long-term variations of cosmic ray diurnal anisotropy are governed not only by solar activity but also by heliospheric magnetic polarity and particle drift effects.
VL  - 14
IS  - 1
ER  -

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Author Information

Ambika Singh

Physics Department, Shaheed Bhagat Singh Government PG College, Pipariya, India

Contact Email

http://orcid.org/0009-0003-6515-0333

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APA Style

Singh, A. (2026). Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity. International Journal of Astrophysics and Space Science, 14(1), 14-19. https://doi.org/10.11648/j.ijass.20261401.12

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ACS Style

Singh, A. Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity. Int. J. Astrophys. Space Sci. 2026, 14(1), 14-19. doi: 10.11648/j.ijass.20261401.12

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AMA Style

Singh A. Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity. Int J Astrophys Space Sci. 2026;14(1):14-19. doi: 10.11648/j.ijass.20261401.12

Copy | Download

@article{10.11648/j.ijass.20261401.12,
  author = {Ambika Singh},
  title = {Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity},
  journal = {International Journal of Astrophysics and Space Science},
  volume = {14},
  number = {1},
  pages = {14-19},
  doi = {10.11648/j.ijass.20261401.12},
  url = {https://doi.org/10.11648/j.ijass.20261401.12},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijass.20261401.12},
  abstract = {The diurnal anisotropy of galactic cosmic ray intensity provides an important diagnostic of solar modulation processes operating in the heliosphere. In the present work, a comprehensive long-term investigation of the diurnal anisotropy has been carried out using pressure-corrected hourly neutron monitor data from two high-latitude stations, Moscow and Kiel, covering a period of 52 years (1965–2016) corresponding to solar cycles 20 to 24. Daily values of the first harmonic diurnal amplitude and phase were obtained through harmonic analysis, from which annual mean values were derived. The long-term relationship between the diurnal amplitude and phase has been examined on annual, solar-cycle, and solar magnetic polarity bases. While day-to-day variations of amplitude and phase are found to be statistically independent, their annual averages exhibit clear solar-cycle-dependent behavior. A weak positive correlation between the diurnal amplitude and phase is observed when all years are considered together. However, a pronounced odd–even solar cycle asymmetry emerges when the data are segregated into odd and even cycles. Strong and statistically significant positive correlations characterize the odd solar cycles, whereas even solar cycles display weak and insignificant correlations. Furthermore, a clear dependence on solar magnetic polarity is observed, with large positive correlations during positive polarity epochs (A > 0) and reduced or reversed correlations during negative polarity epochs (A < 0). These results provide strong observational evidence that long-term variations of cosmic ray diurnal anisotropy are governed not only by solar activity but also by heliospheric magnetic polarity and particle drift effects.},
 year = {2026}
}

Copy | Download

TY  - JOUR
T1  - Polarity Dependence of the Diurnal Anisotropy of Cosmic Rays Intensity
AU  - Ambika Singh
Y1  - 2026/01/30
PY  - 2026
N1  - https://doi.org/10.11648/j.ijass.20261401.12
DO  - 10.11648/j.ijass.20261401.12
T2  - International Journal of Astrophysics and Space Science
JF  - International Journal of Astrophysics and Space Science
JO  - International Journal of Astrophysics and Space Science
SP  - 14
EP  - 19
PB  - Science Publishing Group
SN  - 2376-7022
UR  - https://doi.org/10.11648/j.ijass.20261401.12
AB  - The diurnal anisotropy of galactic cosmic ray intensity provides an important diagnostic of solar modulation processes operating in the heliosphere. In the present work, a comprehensive long-term investigation of the diurnal anisotropy has been carried out using pressure-corrected hourly neutron monitor data from two high-latitude stations, Moscow and Kiel, covering a period of 52 years (1965–2016) corresponding to solar cycles 20 to 24. Daily values of the first harmonic diurnal amplitude and phase were obtained through harmonic analysis, from which annual mean values were derived. The long-term relationship between the diurnal amplitude and phase has been examined on annual, solar-cycle, and solar magnetic polarity bases. While day-to-day variations of amplitude and phase are found to be statistically independent, their annual averages exhibit clear solar-cycle-dependent behavior. A weak positive correlation between the diurnal amplitude and phase is observed when all years are considered together. However, a pronounced odd–even solar cycle asymmetry emerges when the data are segregated into odd and even cycles. Strong and statistically significant positive correlations characterize the odd solar cycles, whereas even solar cycles display weak and insignificant correlations. Furthermore, a clear dependence on solar magnetic polarity is observed, with large positive correlations during positive polarity epochs (A > 0) and reduced or reversed correlations during negative polarity epochs (A < 0). These results provide strong observational evidence that long-term variations of cosmic ray diurnal anisotropy are governed not only by solar activity but also by heliospheric magnetic polarity and particle drift effects.
VL  - 14
IS  - 1
ER  -

Copy | Download