Edward E. DeLuca

Propagating EUV disturbances in the Solar corona: Two-wavelength observations

Quasi-periodic EUV disturbances simultaneously observed in 171 A and 195 A TRACE bandpasses propagating outwardly in a fan-like magnetic structure of a coronal active region are analysed. Time series of disturbances observed in the different bandpasses have a relatively high correlation coefficient (up to about 0.7). The correlation has a tendency to decrease with distance along the structure: this is consistent with an interpretation of the disturbances in terms of parallel- propagating slow magnetoacoustic waves. The wavelet analysis does not show a significant difference between waves observed in different bandpasses. Periodic patterns of two distinct periods: 2-3 min and 5-8 min are detected in both bandpasses, existing simultaneously and at the same distance along the loop, suggesting the nonlinear generation of the second harmonics.

Image stabilization for Airborne Infrared Spectrometer

The Airborne Infrared Spectrometer (AIR-Spec) took measurements of five infrared coronal emission lines from on board a NSF/NCAR airplane during the solar eclipse in August 2017. An open-loop image stabilization system was implemented using a gyroscope and fast steering mirror; 90% of the 60 millisecond exposures had an RMS jitter below 4.6 arcseconds. To increase the exposure time to 1 second, a closed-loop system is proposed using a proportional-integral-derivative (PID) controller and an image cross-correlation algorithm. We predict that 100% of 1 second exposures will have an RMS jitter below 4.6 arcseconds. A detailed analysis of the proposed closed-loop stabilization system is presented.

Abstract: 3D Model Of Slip-Running Reconnection On Solar Sigmoidal Regions

The structure of energy storing magnetic field lines on the Sun is very twisted and contorted. Some of the twist arises from photospheric foot point motion and some is due to currents carried into the corona as fields emerge. The stability of a region depends on both the energy stored (so-called “free” energy) and on the structure of the surrounding nearly potential fields. Free energy is usually contained in these S-shaped regions called sigmoids on the solar corona. The only way to reach lower energy state is to release this free energy, by changing its connectivity. This change in connectivity leads to flares and coronal mass ejections (CMEs) that can affect environments of nearby planets. For this project, we focus on a special kind of connectivity change called slip-running reconnection to create 3D numerical models of flare-producing magnetic fields. By comparing these numerical models to observational data from Atmospheric Imaging Assembly (AIA), we will be able to better explain the evolution of sigmoidal flares from active regions. We are studying a flare fromxa0 Dudik et al 2014 paper (2012 July 12), and a flare from 2015 June 14. Using the Coronal Modeling System (CMS) software, we read the photospheric magnetogram for the specified date and time, compute the potential field, setup the 3D flux rope path, and then relax this flux rope over 60,000 iterations to create a nonlinear force-free field (NLFFF). Using these relaxed models we find the best-fit loops surrounding the flux rope. We then compare these models to the observations in AIA. We compare the magnetic field structure in our models with the observed slipping. For regions near our inserted flux rope, our models successfully correlate with this observation. Further modeling is required, but these initial results suggest that NLFFF modeling may be able to capture realistic 3-D magnetic structures associated with slipping reconnection.

Structure and Dynamics of an Eruptive Prominence on the Quiet Sun

We present preliminary results on the investigation of one polar crown prominence that erupted on 2012 March 11. This prominence is viewed at the east limb by SDO/AIA and displays a simple vertical-thread structure. A bright U-shape (double horn-like) structure is observed surrounding the upper portion of the prominence before the eruption and becomes more prominent during the eruption. When viewed on the disk, STEREO B shows that this prominence is composed of series of vertical threads and displays a loop-like structure during the eruption. We focus on the magnetic support of the prominence by studying the structure and dynamics before and during the eruption using observations from SDO and STEREO. We will also present preliminary DEM analysis of the cavity surrounding the prominence.

Column Density Measurements of a Prominence Observed by AIA

We present column density measurements of a polar crown prominence observed on March 9th, 2012 by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory. The structure was viewed on the east limb by AIA and erupted about 30 hours after the observations shown here. We estimate column density by approximating the obscured background emission to obtain an optical depth. This can then be combined with the absorption cross sections of neutral hydrogen and helium, along with the He:H abundance ratio, to calculate column density. We perform this calculation for the 171, 193, 211, and 335 ˚ AIA passbands.