Theoretical and observed signs of excitation of small-scale magnetic fluctuations in the depth of the Sun

Heading: 
Solar Physics
1Krivodubskij, VN, Kondrashova, NM
1Astronomical Observatory of Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2023, 39(6):58-79
https://doi.org/10.15407/kfnt2023.06.058
Language: Ukrainian
Abstract: 

An actual problem today is the search for observed evidence of the existence of deep small-scale magnetic fields of the Sun. In this regard, we analyzed the proposed by the authors [Sokoloff D., Khlystova A. I. Astron. Nachr. 2010. 331. P. 82—87] a theoretical criterion for separating the contributions to the solar surface magnetism of two qualitatively different mechanisms of a small-scale dynamo, the action of which is hidden in the depths of the solar convection zone (SCZ). The first mechanism ensures the generation of small-scale magnetic fields due to the interaction of turbulent motions with the mean magnetic field (small-scale dynamo 1 of macroscopic MHD), while the second mechanism causes self-excitation of magnetic fluctuations due to turbulent pulsations of highly conductive plasma (diffusive small-scale dynamo 2 of classical MHD). The essence of the proposed criterion is that deep small-scale magnetic fields under certain conditions can lead to violations of Hale’s and Joy’s laws of observed magnetism on the surface of the Sun. Statistical analysis of these disturbances allows us to identify the differences in the evolution of the observed manifestations of two sources of small-scale fields, since the contribution of two deep dynamo mechanisms to surface magnetism varies with the phase of the solar cycle in different ways. Such an important feature is the behavior of the percentage of anti-Hail groups of sunspots (in relation to the total number of sunspots) during the cycles. In the case of small-scale dynamo 1, the percentage of anti-Hale groups is independent of cycle phase, whereas the percentage of anti-Hale groups associated with diffusive small-scale dynamo 2 should reach its maximum value at solar minima. Therefore, the variations of magnetic anomalies make it possible to separate the meager contributions of two small-scale dynamo mechanisms to surface magnetism. In this connection, the task of identifying the markers of a small-scale dynamo in the solar depths from observations becomes relevant. With this in mind, we conducted an analysis of literature data of statistical studies of long series of observed violations of Hale’s and Joy’s laws, which can be caused by the presence of deep small-scale magnetic fluctuations of various origins. In particular, in the work [Sokoloff D., Khlystova A., Abramenko V. Mon. Notic. Roy. Astron. Soc. 2015. 451. P. 1522—1527] on the basis of processing the data of different catalogs for the period 1917—2004, it was demonstrated that the percentage of anti-Hale groups of spots increases during the minima of solar cycles. This testifies to the operation of a diffusive small-scale turbulent dynamo 2 within the SCZ, the efficiency of which becomes noticeable near the minima of the cycles, when the global toroidal magnetic field weakens. As a result of our analysis of six magnetic active regions observed near the minima of the 24th and 25th solar cycles, characteristic violations of Hale’s and Joy’s laws were revealed, which may indicate the influence of a diffusive small-scale dynamo 2 on the evolution of these regions, since it is this source that gives the most noticeable contribution in surface magnetism near cycles minima.
Keywords: dynamo-cycles, magnetic activity of the Sun, magnetic fields, solar convection zone, solar flares, sunspots, turbulent dynamo

Full text (PDF)

References: 

1. Abramenko V. I. (2021) Signature of the turbulent component of the solar dynamo on active region scales and its association with flaring activity. Mon. Notic. Roy. Astron. Soc. 507. 3698-3706. https://doi.org/10.1093/mnras/stab2404

2. Abramenko V. I., Suleymanova R. A., Zhukova A. V. (2023) Magnetic fluxes of solar active regions of different magneto-morphological classes: I. Cyclic variations. Mon. Notic. Roy. Astron. Soc. 518. 4746-4754. https://doi.org/10.1093/mnras/stac3338

3. Abramenko V. I., Zhukova A. V., Kutsenko A. S. (2018) Contributions from different-type active regions into the total solar unsigned magnetic flux. Geomag. Aeron. 58. 1159-1169. https://doi.org/10.1134/S0016793218080224

4. Alfven H. (1942) On the existence of electromagnetic-hydrodynamic waves. Arkiv f. Mat., Astron. o. Fys. 29B. 1-7; Nature. 150. 405-406. https://doi.org/10.1038/150405d0

5. Bekki Y., Cameron R. H. (2023) Three-dimensional non-kinematic simulation of the post-emergence evolution of bipolar magnetic regions and the Babcock-Leighton dynamo of the Sun? Astron. and Astrophys. 670. A101. 18. https://doi.org/10.1051/0004-6361/202244990

6. Benevolenskaya E. E. (1995) Double magnetic cycle of solar activity. Solar Phys. 161. 1-8. https://doi.org/10.1007/BF00732080

7. Benevolenskaya E. E. (1998) A model of the double magnetic cycle of the Sun. Astrophys. J. 509. L49-L52. https://doi.org/10.1086/311755

8. Biermann L., Schlter A. (1951) Cosmic radiation and cosmic magnetic fields. II. Origin of cosmic magnetic fields. Phys. Rev. 82. 863-868. https://doi.org/10.1103/PhysRev.82.863

9. Blackman E. G., Field G. B. (2002) New dynamical mean-field dynamo theory and closure approach. Phys. Rev. Lett. 89. 265007. https://doi.org/10.1103/PhysRevLett.89.265007

10. Brandenburg A., Sokoloff D., Subramanian K. (2012) Current status of turbulent dynamo theory. From large-scale to small-scale dynamos. Space Sci. Rev. 169. 123-159. https://doi.org/10.1007/s11214-012-9909-x

11. Brandenburg A., Subramanian K. (2005) Astrophysical magnetic fields and nonlinear dynamo theory. Phys. Reports. 417. 1-285. https://doi.org/10.1016/j.physrep.2005.06.005

12. Charbonneau P. (2020) Dynamo models of the solar cycle. Living Rev. Solar Phys. 7. 1-104. https://doi.org/10.1007/s41116-020-00025-6

13. Choudhuri A.R. (1989) The evolution of loop structures in flux rings within solar convection zone. Solar Phys. 123. 217-239. https://doi.org/10.1007/BF00149104

14. Fan Y. (2009) Magnetic fields in the solar convection zone. Living Rev. Solar Phys. 6. 1-96. https://doi.org/10.12942/lrsp-2009-4

15. Hale G. E., Ellerman F., Nicholson S. B., Joy A. H. (1919) The magnetic polarity of sun-spots. Astrophys. J. 49. 153-186. https://doi.org/10.1086/142452

16. Hale G. E., Nicholson S. B. (1925) The low of sun-spot polarity. Astrophys. J. 62. 270. https://doi.org/10.1086/142933

17. Hathaway D. H. (2015) The Solar Cycle. Living Rev. Solar Phys. 12. 1-87. https://doi.org/10.1007/lrsp-2015-4

18. Howard R. F. (1991) Axial tilt angles of sunspot groups. Solar Phys. 136. 251-262. https://doi.org/10.1007/BF00146534

19. Kazantsev A. P. (1968) Enhancement of a magnetic field by a conducting fluid. Sov. J. Exp. Theor. Phys. 26. 1031.

20. Kraichnan R. H., Nagarajan S. (1967) Growth of turbulent magnetic fields. Phys. Fluid. 10. 859-870. https://doi.org/10.1063/1.1762201

21. Krause F., Rdler K.-H. (1980) Mean field magnetohydrodynamics and dynamo theory. Oxford: Pergamon Press, Ltd., 271 p.

22. Krivodubskij V. N. (1973) Electrical conductivity of the matter in subphotosheric layers of the Sun. Problems of space physics. 8. 1-15. [in Russian].

23. Krivodubskij V. N. (2005) Turbulent dynamo near tachocline and reconstruction of azimuthal magnetic field in the solar convection zone. Astron. Nachr. 326. 61-74. https://doi.org/10.1002/asna.200310340

24. Krivodubskij V. N. (2021) Role of rotational radial magnetic advection in possible explaining a cycle with two peaks. Advances in Space Research. 68. 3943-3955. https://doi.org/10.1016/j.asr.2021.07.007

25. Kryvodubskyj V. N. (2006) Dynamo parameters of the solar convection zone. Kinematics and Phys. Celestial Bodies. 22. 1-20.

26. Li J. (2018) A systematic study of Hale and anti-Hale sunspot physical parameters. Astrophys. J. 867. 89. 16. https://doi.org/10.3847/1538-4357/aae31a

27. Li J., Ulrich R. K. (2012) Long-term measurements of sunspot magnetic tilt angles. Astrophys. J. 758. 115. 12. https://doi.org/10.1088/0004-637X/758/2/115

28. McClintock B. H., Norton A. A., Li J. (2014) Re-examining sunspot tilt angle to include anti-hale statistics. Astrophys. J. 797. 130. 10. https://doi.org/10.1088/0004-637X/797/2/130

29. Munoz-Jaramillo A., Navarrete B., Campusano L. E. (2021) Solar anti-Hale bipolar magnetic regions: a distinct population with systematic properties. Astrophys. J. 920. 31. 11. https://doi.org/10.3847/1538-4357/ac133b

30. Nagy M., Lemerle A., Labonville F., Petrovay K., Charbonneau P. (2017) The effect of "rogue" active regions on the solar cycle. Solar Phys. 292. 167. 22. https://doi.org/10.1007/s11207-017-1194-0

31. Popova E. P., Potemina K. A., Yukhina N. A. (2015) Double cycle of solar activity in a two-layer medium. Geomagnetism and Aeronomy. 54. 877-881. https://doi.org/10.1134/S0016793214070111

32. Popova E., Zharkova V., Zharkov S. (2013) Probing latitudinal variations of the solar magnetic field in cycles 21-23 by Parker's two-layer dynamo model with meridional circulation. Ann. Geophys. 31. 2023-2028. https://doi.org/10.5194/angeo-31-2023-2013

33. Rdler K.-H., Kleeorin N., Rogachevskii I. (2003) The mean electromotive force for MHD turbulence: the case of a weak mean magnetic field and slow rotation. Geophys. Astrophys. Fluid Dyn. 97. 249-274. https://doi.org/10.1080/0309192031000151212

34. Richardson R. S. (1948) Sunspot groups of irregular magnetic polarity. Astrophys. J. 107. 78. https://doi.org/10.1086/144988

35. Shepherd S. J., Zharkov S. I., Zharkova V. V. (2014) Prediction of solar activity from solar background magnetic field variations in cycles 21-23. Astrophys. J. 795. 46-53. https://doi.org/10.1088/0004-637X/795/1/46

36. Smith S. F., Howard R. (1968) Magnetic classification of active regions. In: Kiepenheuer, K.O. (ed.) Structure and Development of Solar Active Regions, IAU Symp. 35. 33. https://doi.org/10.1007/978-94-011-6815-1_5

37. Sokoloff D., Khlystova A. I. (2010) The solar dynamo in the light of the distribution of various sunspot magnetic classes over butterfly diagram. Astron. Nachr. 331. 82-87. https://doi.org/10.1002/asna.200911300

38. Sokoloff D., Khlystova A., Abramenko V. (2015) Solar small-scale dynamo and polarity of sunspot groups. Mon. Notic. Roy. Astron. Soc. 451. 1522-1527. https://doi.org/10.1093/mnras/stv1036

39. Stenflo J. O., Kosovichev A. G. (2012) Bipolar magnetic regions on the Sun: global analysis of the SOHO/MDI data set. Astrophys. J. 745. 129. 12. https://doi.org/10.1088/0004-637X/745/2/129

40. Sur S., Brandenburg A., Subramanian K. (2008) Kinematic -effect in isotropic turbulence simulations. Mon. Notic. Roy. Astron. Soc. 385. L15-L19. https://doi.org/10.1111/j.1745-3933.2008.00423.x

41. Vitinsky Y. I. (1968) On sunspot groups with irregular magnetic polarities. Byull. Solnechnye Dannye. 9. 86.

42. Wang Y.-M., Sheeley J. N. R. (1989) Average properties of bipolar magnetic regions during sunspot cycle-21. Solar Phys. 124. 81-100. https://doi.org/10.1007/BF00146521

43. Xu Zh., Yan X., Yang L., et al. (2022) Evolution of an emerging anti-Hale region and its associated eruptive solar flares in NOAA AR 12882. Astrophys. J. Lett. 937. L11. 9. https://doi.org/10.3847/2041-8213/ac8fef

44. Zharkova V. V., Shepherd S. J., Zharkov S. I. (2012) Principal component analysis of background and sunspot magnetic field variations during solar cycles 21-23. Mon. Notic. Roy. Astron. Soc. 424. 2943-2953. https://doi.org/10.1111/j.1365-2966.2012.21436.x

45. Zhukova A., Khlystova A., Abramenko V., Sokoloff D. (2020) A catalog of bipolar active regions violating the Hale polarity law, 1989 - 2018. Solar Phys. 295. 165. 18. https://doi.org/10.1007/s11207-020-01734-9

46. Zhukova A., Khlystova A., Abramenko V., Sokoloff D. (2022) Synthetic solar cycle for active regions violating the Hale's polarity law. Mon. Notic. Roy. Astron. Soc. 512. 1365¬1370. https://doi.org/10.1093/mnras/stac597

47. Zeldovich Y. B., Ruzmaikin A. A., Sokoloff D. D. (1990) The almighty chance. World scientific lecture notes in physics, Singapore: World Scientific Publication. https://doi.org/10.1142/0862