Solar Physics

, Volume 290, Issue 7, pp 2055–2076

Null Point Distribution in Global Coronal Potential Field Extrapolations

Article

Abstract

Magnetic null points are points in space where the magnetic field is zero. Thus, they can be important sites for magnetic reconnection by virtue of the fact that they are weak points in the magnetic field and also because they are associated with topological structures, such as separators, which lie on the boundary between four topologically distinct flux domains and therefore are also locations where reconnection occurs. The number and distribution of nulls in a magnetic field acts as a measure of the complexity of the field.

In this article, the numbers and distributions of null points in global potential field extrapolations from high-resolution synoptic magnetograms are examined. Extrapolations from magnetograms obtained with the Michelson Doppler Imager (MDI) are studied in depth and compared with those from high-resolution SOlar Long-time Investigations of the Sun (SOLIS) and Heliospheric Magnetic Imager (HMI).

The fall-off in the density of null points with height is found to follow a power law with a slope that differs depending on whether the data are from solar maximum or solar minimum. The distribution of null points with latitude also varies with the cycle as null points form predominantly over quiet-Sun regions and avoid active-region fields. The exception to this rule are the null points that form high in the solar atmosphere, and these null points tend to form over large areas of strong flux in active regions.

From case studies of data acquired with the MDI, SOLIS, and HMI, it is found that the distribution of null points is very similar between data sets, except, of course, that there are far fewer nulls observed in the SOLIS data than in the cases from MDI and HMI due to its lower resolution.

Keywords

Magnetic topology Magnetic fields Global corona Potential fields 

References

  1. Al-Hachami, A.K., Pontin, D.I.: 2010, Magnetic reconnection at 3D null points: effect of magnetic field asymmetry. Astron. Astrophys. 512, A84. DOI. ADS. CrossRefADSGoogle Scholar
  2. Altschuler, M.D., Newkirk, G.: 1969, Magnetic fields and the structure of the solar corona. I: Methods of calculating coronal fields. Solar Phys. 9, 131. DOI. ADS. CrossRefADSGoogle Scholar
  3. Antiochos, S.K., DeVore, C.R., Klimchuk, J.A.: 1999, A model for solar coronal mass ejections. Astrophys. J. 510, 485. DOI. ADS. CrossRefADSGoogle Scholar
  4. Aulanier, G., DeLuca, E.E., Antiochos, S.K., McMullen, R.A., Golub, L.: 2000, The topology and evolution of the Bastille Day flare. Astrophys. J. 540, 1126. DOI. ADS. CrossRefADSGoogle Scholar
  5. Biskamp, D.: 2000, Magnetic Reconnection in Plasmas. Cambridge University Press, Cambridge. ADS. CrossRefGoogle Scholar
  6. Bulanov, S.V., Echkina, E.Y., Inovenkov, I.N., Pegoraro, F.: 2002, Current sheet formation in three-dimensional magnetic configurations. Phys. Plasmas 9, 3835. DOI. ADS. MathSciNetCrossRefADSGoogle Scholar
  7. Close, R.M., Parnell, C.E., Priest, E.R.: 2004, Separators in 3D quiet-Sun magnetic fields. Solar Phys. 225, 21. DOI. ADS. CrossRefADSGoogle Scholar
  8. Cook, G.R., Mackay, D.H., Nandy, D.: 2009, Solar cycle variations of coronal null points: Implications for the magnetic breakout model of coronal mass ejections. Astrophys. J. 704, 1021. DOI. ADS. CrossRefADSGoogle Scholar
  9. Dungey, J.W.: 1953, Conditions for the occurrence of electrical discharges in astrophysical systems. Phil. Mag. 44, 725. CrossRefGoogle Scholar
  10. Fletcher, L., López Fuentes, M.C., Mandrini, C.H., Schmieder, B., Démoulin, P., Mason, H.E., Young, P.R., Nitta, N.: 2001, A relationship between transition region brightenings, abundances, and magnetic topology. Solar Phys. 203, 255. DOI. ADS. CrossRefADSGoogle Scholar
  11. Freed, M.S., Longcope, D.W., McKenzie, D.E.: 2015, Three-year global survey of coronal null points from potential-field-source-surface (PFSS) modeling and Solar Dynamics Observatory (SDO) observations. Solar Phys. 290, 467. DOI. ADS. CrossRefADSGoogle Scholar
  12. Galsgaard, K., Pontin, D.I.: 2011, Steady state reconnection at a single 3D magnetic null point. Astron. Astrophys. 529, A20. DOI. ADS. CrossRefADSGoogle Scholar
  13. Haynes, A.L., Parnell, C.E.: 2007, A trilinear method for finding null points in a three-dimensional vector space. Phys. Plasmas 14(8), 082107. DOI. ADS. CrossRefADSGoogle Scholar
  14. Haynes, A.L., Parnell, C.E., Galsgaard, K., Priest, E.R.: 2007, Magnetohydrodynamic evolution of magnetic skeletons. Proc. Roy. Soc. London Ser. A, Math. Phys. Sci. 463, 1097. DOI. ADS. MathSciNetCrossRefADSGoogle Scholar
  15. Lau, Y.-T., Finn, J.M.: 1990, Three-dimensional kinematic reconnection in the presence of field nulls and closed field lines. Astrophys. J. 350, 672. DOI. ADS. MathSciNetCrossRefADSGoogle Scholar
  16. Longcope, D.W.: 2001, Separator current sheets: Generic features in minimum-energy magnetic fields subject to flux constraints. Phys. Plasmas 8, 5277. DOI. ADS. CrossRefADSGoogle Scholar
  17. Longcope, D.W.: 2005, Topological methods for the analysis of solar magnetic fields. Living Rev. Solar Phys. 2, 7. DOI. ADS. CrossRefADSGoogle Scholar
  18. Longcope, D.W., Brown, D.S., Priest, E.R.: 2003, On the distribution of magnetic null points above the solar photosphere. Phys. Plasmas 10, 3321. DOI. ADS. CrossRefADSGoogle Scholar
  19. Longcope, D.W., Parnell, C.E.: 2009, The number of magnetic null points in the quiet Sun corona. Solar Phys. 254, 51. DOI. ADS. CrossRefADSGoogle Scholar
  20. Longcope, D.W., McKenzie, D.E., Cirtain, J., Scott, J.: 2005, Observations of separator reconnection to an emerging active region. Astrophys. J. 630, 596. DOI. ADS. CrossRefADSGoogle Scholar
  21. Longcope, D., Parnell, C., DeForest, C.: 2009, The density of coronal null points from Hinode and MDI. In: Lites, B., Cheung, M., Magara, T., Mariska, J., Reeves, K. (eds.) The Second Hinode Science Meeting: Beyond Discovery-Toward Understanding, Astronomical Society of the Pacific Conference Series 415, 178. ADS. Google Scholar
  22. Masson, S., Pariat, E., Aulanier, G., Schrijver, C.J.: 2009, The nature of flare ribbons in coronal null-point topology. Astrophys. J. 700, 559. DOI. ADS. CrossRefADSGoogle Scholar
  23. Parker, E.N.: 1957, Sweet’s mechanism for merging magnetic fields in conducting fluids. J. Geophys. Res. 62, 509. DOI. ADS. CrossRefADSGoogle Scholar
  24. Parnell, C.E., Haynes, A.L., Galsgaard, K.: 2008, Recursive reconnection and magnetic skeletons. Astrophys. J. 675, 1656. DOI. ADS. CrossRefADSGoogle Scholar
  25. Parnell, C.E., Haynes, A.L., Galsgaard, K.: 2010, Structure of magnetic separators and separator reconnection. J. Geophys. Res. 115, 2102. DOI. ADS. CrossRefGoogle Scholar
  26. Parnell, C.E., Maclean, R.C., Haynes, A.L.: 2010, The detection of numerous magnetic separators in a three-dimensional magnetohydrodynamic model of solar emerging flux. Astrophys. J. Lett. 725, L214. DOI. ADS. CrossRefADSGoogle Scholar
  27. Petschek, H.E.: 1964, Magnetic field annihilation. In: AAS-NASA Symposium on the Physics of Solar Flares (NASA Special Publication) 50, 425. ADS. Google Scholar
  28. Platten, S.J., Parnell, C.E., Haynes, A.L., Priest, E.R., Mackay, D.H.: 2014, The solar cycle variation of topological structures in the global solar corona. Astron. Astrophys. 565, A44. DOI. ADS. CrossRefADSGoogle Scholar
  29. Pontin, D.I., Galsgaard, K.: 2007, Current amplification and magnetic reconnection at a three-dimensional null point: Physical characteristics. J. Geophys. Res. 112, 3103. DOI. ADS. CrossRefGoogle Scholar
  30. Pontin, D.I., Priest, E.R., Galsgaard, K.: 2013, On the nature of reconnection at a solar coronal null point above a separatrix dome. Astrophys. J. 774, 154. DOI. ADS. CrossRefADSGoogle Scholar
  31. Priest, E., Forbes, T.: 2000, Magnetic Reconnection. Cambridge University Press, Cambridge. ADS. CrossRefGoogle Scholar
  32. Priest, E.R., Pontin, D.I.: 2009, Three-dimensional null point reconnection regimes. Phys. Plasmas 16(12), 122101. DOI. ADS. CrossRefADSGoogle Scholar
  33. Régnier, S., Parnell, C.E., Haynes, A.L.: 2008, A new view of quiet-Sun topology from Hinode/SOT. Astron. Astrophys. 484, L47. DOI. ADS. CrossRefADSGoogle Scholar
  34. Rickard, G.J., Titov, V.S.: 1996, Current accumulation at a three-dimensional magnetic null. Astrophys. J. 472, 840. DOI. ADS. CrossRefADSGoogle Scholar
  35. Schatten, K.H., Wilcox, J.M., Ness, N.F.: 1969, A model of interplanetary and coronal magnetic fields. Solar Phys. 6, 442. DOI. ADS. CrossRefADSGoogle Scholar
  36. Schrijver, C.J., Title, A.M.: 2002, The topology of a mixed-polarity potential field, and inferences for the heating of the quiet solar corona. Solar Phys. 207, 223. DOI. ADS. CrossRefADSGoogle Scholar
  37. Sweet, P.A.: 1958, The neutral point theory of solar flares. In: Lehnert, B. (ed.) Electromagnetic Phenomena in Cosmical Physics, IAU Symposium 6, 123. ADS. Google Scholar
  38. Wyper, P., Jain, R.: 2010, Torsional magnetic reconnection at three dimensional null points: A phenomenological study. Phys. Plasmas 17(9), 092902. DOI. ADS. CrossRefADSGoogle Scholar
  39. Wyper, P.F., Pontin, D.I.: 2014, Non-linear tearing of 3D null point current sheets. Phys. Plasmas 21(8), 082114. DOI. ADS. CrossRefADSGoogle Scholar
  40. Xiao, C.J., Wang, X.G., Pu, Z.Y., Zhao, H., Wang, J.X., Ma, Z.W., Fu, S.Y., Kivelson, M.G., Liu, Z.X., Zong, Q.G., Glassmeier, K.H., Balogh, A., Korth, A., Reme, H., Escoubet, C.P.: 2006, In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth’s magnetotail. Nat. Phys. 2, 478. DOI. ADS. CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  1. 1.Department of Mathematical SciencesDurham UniversityDurhamUK
  2. 2.School of Mathematics and StatisticsUniversity of St AndrewsSt Andrews, FifeUK

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