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

摘要

This article compiles and examines a comprehensive coronalmagnetic-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 coronawere predicted from the PFSS model between Carrington Rotations (CR) 2098 (June2010) and 2139 (July 2013). These locations were manually inspected, usingcontrast-enhanced SDO/AIA images in 171 angstroms at the east and west solarlimb, for structures associated with nulls. A Kolmogorov--Smirnov (K--S) testshowed a statistically significant difference between observed and predictedlatitudinal distributions of null points. This finding is explored further toshow that the observability of null points could be affected by the Sun'sasymmetric hemisphere activity. Additional K--S tests show no effect onobservability related to eigenvalues associated with the fan and spinestructure surrounding null points or to the orientation of spine. We find thatapproximately 31% of nulls obtained from the PFSS model were observed inSDO/AIA images at one of the solar limbs. An observed null on the east solarlimb had a 51.6% chance of being observed on the west solar limb. Predictednull points going back to CR 1893 (March 1995) were also used for comparingradial and latitudinal distributions of nulls to previous work and to test forcorrelation of solar activity to the number of predicted nulls.