Abstract and keywords
Abstract (English):
Diffusion and electromagnetic mechanisms determine the formation of sporadic Forbush decreases. The diffusion mechanism affects the Forbush decrease amplitude in the turbulent layer, and the part of the coronal mass ejection preceding the magnetic cloud, and its efficiency depends on the level of magnetic field turbulence. The electromagnetic mechanism works in a magnetic cloud, and its efficiency depends on the intensity of regular magnetic and electric fields. We analyze solar wind parameters and cosmic ray density, using the superposed epoch analysis. In 1996–2006, 23 strong Forbush decreases (amplitude >5 %) were detected. The average amplitude of 7 % is equally formed by both mechanisms. The events can be divided into 2 groups depending on the contribution of the mechanisms to Forbush decrease amplitude. Group 1 includes the strongest Forbush decreases (amplitude=8.5 %), formed by both diffusion and electromagnetic mechanisms. The diffusion mechanism forms 0.26 amplitude, and the electromagnetic mechanism is responsible for 0.74 one. In group 2, the averege amplitude Forbush decrease =5.7 %, the diffusion mechanism forms 0.79 of amplitude; and the electromagnetic one, 0.21. The spatial distributions of the mean values of the medium parameters in the region of disturbances in the groups differ. This difference can be explained by the fact that Forbush decrease amplitude in groups 1 and 2 are formed in the central and peripheral parts of coronal mass ejection respectively.

cosmic rays, coronal mass ejection, Forbush decrease, solar wind, interplanetary magnetic field, shock, magnetic cloud
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1. Abunin A., Abunina M., Belov A., Eroshenko E., Oleneva V., Yanke V., Mavromichalaki H., Papaioannou A. The impact of magnetic clouds on the density and the first harmonic of the cosmic ray anisotropy. ICRC. 2013, vol. 33, 1618.

2. Badruddin B., Venkatesan D., Zhu B.Y. Study and effect of magnetic clouds on the transient modulation of cosmic-ray intensity. Solar Phys. 1991, vol. 134, no. 1, pp. 203-209. DOI:

3. Belov A.V. Forbush effects and their connection with solar, interplanetary and geomagnetic phenomena. Universal Heliophysical Processes. 2009, vol. 257, pp. 43-450. DOI:

4. Belov A., Abunin A., Abunina M., Eroshenko E., Oleneva V., Yanke V., Papaioannou A., Mavromichalaki H., Gopalswamy N., Yashiro S. Coronal mass ejections and non-recurrent Forbush decreases. Solar Phys. 2014, vol. 289, no. 10, pp. 394-3960. DOI:

5. Belov A., Abunin A., Abunina M., Eroshenko E., Oleneva V., Yanke V., Papaioannou A., Mavromichalaki H. Galactic cosmic ray density variations in magnetic clouds. Solar Phys. 2015, vol. 290, no. 5, pp. 1429-1444. DOI:

6. Belov A., Eroshenko E., Yanke V., Oleneva V., Abunin A., Abunina M., Papaioannou A., Mavromichalaki H. The Global Survey Method applied to ground-level cosmic ray measurements. Solar Phys. 2018, vol. 293, no. 4, 68. DOI:

7. Benella S., Laurenza M., Vainio R., Grimani C., Consolini G., Hu Q., Afanasiev A. A New method to model magnetic cloud-driven Forbush decreases: The 2016 August 2 event. Astrophys. J. 2020, vol. 901, no. 1, 21. DOI:

8. Bothmer V., Schwenn R. The structure and origin of magnetic clouds in the solar wind. Ann. Geophys. 1998, vol. 16, no. 1, pp. 1-24. DOI:

9. Cane H.V., Richardson I.G., Wibberenz G. The response of energetic particles to the presence of ejecta material. International Cosmic Ray Conference. 1995, vol. 4, p. 377.

10. Forbush S.E. On the effects in cosmic-ray intensity observed during the recent magnetic storm. Physical Review. 1937, vol. 51, no. 12, pp. 1108-1109. DOI: 51.1108.3.

11. Hess V. F., Demmelmair A. World-wide effect in cosmic ray intensity, as observed during a recent magnetic storm. Nature. 1937, vol. 140, no. 3538, pp. 316-317. DOI: 10.1038/ 140316a0.

12. Kadokura A., Nishida A. Two-dimensional numerical modeling of the cosmic ray storm. J. Geophys. Res. 1986, vol. 91, no. A1, pp. 13-30. DOI:

13. Kilpua E., Koskinen H.E.J., Pulkkinen T.I. Coronal mass ejections and their sheath regions in interplanetary space. Living Reviews in Solar Physics. 2017, vol. 14, no. 1, 5. DOI:

14. Krittinatham W., Ruffolo D. Drift orbits of energetic particles in an interplanetary magnetic flux rope. Astrophys. J. 2009, vol. 704, no. 1, pp. 831-841. DOI:

15. Krymskii G.F., Transkii I.A., Elshin E.K. Piston shock waves in the interplanetary medium and Forbush effects. Geomagnetizm i Aeronomiya [Geomagnetism and Aeronomy]. 1974, vol. 14, no. 3, pp. 407-410. (In Russian).

16. Laitinen T., Dalla S. Cosmic ray access from external field lines to an ICME fluxrope. 43rd COSPAR Scientific Assembly. Held 28 January - 4 February. 2021, vol. 43, 866.

17. Lockwood J.A., Webber W.R., Debrunner H. Forbush decreases and interplanetary magnetic field disturbances: Association with magnetic clouds. J. Geophys. Res. 1991, vol. 96, no. A7, pp. 11587-11604. DOI:

18. Luo X., Potgieter M.S., Zhang M., Feng X. A numerical study of Forbush decreases with a 3D cosmic-ray modulation model based on an SDE approach. Astrophys. J. 2017, vol. 839, no. 1, 53. DOI:

19. Owens M.J. Do the legs of magnetic clouds contain twisted flux-rope magnetic fields? Astrophys. J. 2016, vol. 818, no. 2, rr. 1-5. DOI:

20. Petukhova A., Petukhov S. Toroidal models of magnetic field with twisted structure. Solar-Terr. Phys. 2019, vol. 5, no. 2. pp. 69-75. DOI:

21. Petukhova A.S., Petukhov I.S., Petukhov S.I. Theory of the formation of Forbush decrease in a magnetic cloud: Dependence of Forbush decrease characteristics on magnetic cloud parameters. Astrophys. J. 2019, vol. 880, no. 1, p. 17. DOI:

22. Petukhova A.S., Petukhov I.S., Petukhov S.I. Forbush decrease characteristics in a magnetic cloud. Space Weather. 2020, vol. 18, no. 12, e02616. DOI:

23. Reames D.V., Kahler S.W., Tylka A.J. Anomalous cosmic rays as probes of magnetic clouds. Astrophys. J. 2009, vol. 700, no. 2, pp. L196-L199. DOI:

24. Richardson I.G., Cane H.V. Galactic cosmic ray intensity response to interplanetary coronal mass ejections/magnetic clouds in 1995-2009. Solar Phys. 2011, vol. 270, no. 2, pp. 609-627. DOI:

25. Tortermpun U., Ruffolo D., Bieber J.W. Galactic cosmic-ray anistropy during the Forbush decrease starting 2013 April 13. Astrophys. J. 2018, vol. 852, no. 2, L26. DOI:

26. URL: (accessed March 1, 2023).

27. URL: (accessed March 1, 2023).

28. URL: (accessed March 1, 2023).

29. URL: (accessed March 1, 2023).

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