We perform a detailed analysis of the thermal structure of the region above the post-eruption arcade for a flare that occurred on 2011 October 22. During this event, a sheet of hot plasma is visible above the flare loops in the 131Å bandpass of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). Supra-arcade downflows (SADs) are observed traveling sunward through the post-eruption plasma sheet. We calculate differential emission measures using the AIA data and derive an emission measure weighted average temperature in the supra-arcade region. In areas where many SADs occur, the temperature of the supra-arcade plasma tends to increase, while in areas where no SADs are observed, the temperature tends to decrease. We calculate the plane-of-sky velocities in the supra-arcade plasma and use them to calculate the potential heating due to adiabatic compression and viscous heating. Ten of the 13 SADs studied have noticeable signatures in both the adiabatic and the viscous terms. The adiabatic heating due to compression of plasma in front of the SADs is on the order of 0.1 -0.2 MK/s, which is similar in magnitude to the estimated conductive cooling rate. This result supports the notion that SADs contribute locally to the heating of plasma in the supra-arcade region. We also find that in the region without SADs, the plasma cools at a rate slower than the estimated conductive cooling, indicating additional heating mechanisms may act globally to keep the plasma temperature high.

This article compiles and examines a comprehensive coronal magneticnull-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 171Å 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.

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 (QPs). These plasma flow characteristics can be utilized to improve our understanding of how the prominence maintains a stable magnetic field configuration. Three different contrastenhanced 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 thathas been observed in many QPs. The kinetic energy power spectral density (PSD) 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 PSD reveals thata different scaling relationship exists between the observed prominence structure and velocity maps. All of the prominences exhibited an inertial range of at least k 0.8 2.0 rads Mm 1   -. Quasiperiodic 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 (ò ∼ 0.22-7.04 km s 2 2 -) and enstrophy density (ω ∼ 1.43-13.69 10 s 16 2 --) associated with each prominence.

Abstract-Planetary formation is an efficient process now thought to take place on a relatively short astronomical time scale. Recent observations have shown that the dust surrounding a protostar emits more efficiently at longer wavelengths as the protoplanetary disk evolves, suggesting that the dust particles are coagulating into fluffy aggregates, "much as dust bunnies form under a bed."One poorly understood problem in this coagulation process is the manner in which micron-sized, charged grains form the fractal aggregate structures now thought to be the precursors of protoplanetary disk evolution. This study examines the characteristics of such fractal aggregates formed by the collision of spherical monomers and aggregates where the charge is distributed over the aggregate structure. The aggregates are free to rotate due to collisions and dipole-dipole electrostatic interactions. Comparisons are made for different precursor size distributions and like-charged, oppositelycharged, and neutral grains.