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

Michael Freed   Submitted: 2016-02-09 20:14

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 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.

Authors: M. S. Freed, D. W. Longcope, and D. E. McKenzie
Projects: SDO-AIA

Publication Status: Published
Last Modified: 2016-02-10 10:10
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Analysis of Flows Inside Quiescent Prominences as Captured by Hinode/Solar Optical Telescope  

Michael Freed   Submitted: 2016-02-09 19:54

Developing an understanding of how magnetic fields can become entangled in a prominence is important for predicting a possible eruption. This work investigates the kinetic energy and vorticity associated with plasma motion residing inside quiescent prominences. These plasma flow characteristics can be utilized to improve our understanding of how the prominence maintains a stable magnetic field configuration. Three different contrast-enhanced solar prominence observations from Hinode/Solar Optical Telescope were used to construct velocity maps - in the plane of the sky - via a Fourier local correlation tracking program. The resulting velocities were then used to perform the first ever analysis of the two-dimensional kinetic energy and enstrophy spectra of a prominence. Enstrophy is introduced here as a means of quantifying the vorticity which has been observed in many quiescent prominences. The kinetic energy power spectral density produced indices ranging from -1.00 to -1.60. There was a consistent anisotropy in the kinetic energy spectrum of all three prominences examined. Examination of the intensity power spectral density reveals a different scaling relationship exists between the observed prominence structure and velocity maps. All of the prominences exhibited an inertial range of at least 0.8 ≤ k≤ 2.0 rads Mm-1. Quasi-periodic oscillations were also detected in the centroid of the velocity distributions for one prominence. Additionally, a lower limit was placed on the kinetic energy density (ε   ~ 0.22-7.04 km2s-2) and enstrophy density (ω   ~ 1.43-13.69 x 10-16   s-2) associated with each prominence.

Authors: M. S. Freed, D. E. McKenzie, D. W. Longcope, and M. Wilburn
Projects: Hinode/SOT

Publication Status: Published
Last Modified: 2016-02-10 10:11
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Three-Year Global Survey of Coronal Null Points from Potential-Field-Source-Surface (PFSS) Modeling and Solar Dynamics Observatory (SDO) Observations
Analysis of Flows Inside Quiescent Prominences as Captured by Hinode/Solar Optical Telescope

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