Solar Physics

, Volume 290, Issue 2, pp 467–490 | Cite as

Three-Year Global Survey of Coronal Null Points from Potential-Field-Source-Surface (PFSS) Modeling and Solar Dynamics Observatory (SDO) Observations

  • M. S. FreedEmail author
  • D. W. Longcope
  • D. E. McKenzie


This article compiles and examines a comprehensive coronal magnetic-null-point survey created by potential-field-source-surface (PFSS) modeling and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. The locations of 582 potential magnetic null points in the corona were predicted from the PFSS model between Carrington Rotations (CR) 2098 (June 2010) and 2139 (July 2013). These locations were manually inspected, using contrast-enhanced SDO/AIA images in 171 Å at the East and West solar limb, for structures associated with nulls. A Kolmogorov–Smirnov (K–S) test showed a statistically significant difference between observed and predicted latitudinal distributions of null points. This finding is explored further to show that the observability of null points could be affected by the Sun’s asymmetric hemisphere activity. Additional K–S tests show no effect on observability related to eigenvalues associated with the fan and spine structure surrounding null points or to the orientation of the spine. We find that approximately 31 % of nulls obtained from the PFSS model were observed in SDO/AIA images at one of the solar limbs. An observed null on the East solar limb had a 51.6 % chance of being observed on the West solar limb. Predicted null points going back to CR 1893 (March 1995) were also used for comparing radial and latitudinal distributions of nulls to previous work and to test for correlation of solar activity to the number of predicted nulls.


Sun: activity Sun: corona Sun: magnetic fields 



We would like to thank the Montana Space Grant Consortium for a fellowship to conduct this work. This work was also partially supported by NASA under contract SP02H3901R from Lockheed-Martin to Montana State University. The authors also thank Spiro Antiochos and Sophie Masson for their useful discussions, and the anonymous referee for their helpful feedback.

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • M. S. Freed
    • 1
    Email author
  • D. W. Longcope
    • 1
  • D. E. McKenzie
    • 1
  1. 1.Department of PhysicsMontana State UniversityBozemanUSA

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