Student Name: Christine Carvajal
Advisor Name: Dr. Navdeep Panesar (Lockheed Martin Solar and Astrophysics Laboratory)
Project Title: EUV Campfires Observed by Solar Dynamics Observatory in Areas of Weak Magnetic Flux in a Coronal Hole
Project Description:
Solar campfires are small-scale coronal brightenings that are usually rooted at an edge of a chromospheric network clump or lane (Berghmans et al. 2021), and were recently well observed by Solar Orbiter’s Extreme Ultraviolet Imager (EUI). Campfires show jet-like, loop-like, dot-like, or complex coronal structure. They usually are seen to reside above a photospheric magnetic neutral line, and usually show cool-plasma (dark) structure in EUV images (Panesar et al. 2021). In two days in a central-disk positive-polarity coronal hole, using Helioviewer to view AIA 211 Å images (which show the dark coronal hole well) and HMI magnetograms, we found 24 campfire-like events that are not located on any discernible neutral line in very weak (near HMI-noise-level) magnetic-field locations. We examined these 24 campfires with data from the Solar Dynamics Observatory: EUV images from the 304, 171, 193 and 211 Å channels of SDO’s Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms from SDO’s Helioseismic and Magnetic Imager (HMI). We prepared and analyzed these with routines in SunPy and SolarSoft IDL. We examined whether each campfire sits on any HMI-detectable magnetic flux; if yes, then whether they sit on HMI-detectable magnetic neutral lines; and, if so, what triggers the sudden production of the campfire, e.g., flux emergence and/or flux cancellation. We find (1) 12 of the 24 events did not sit on an HMI-detectable neutral line, (2) 5 of these 12 sit next to a single-polarity flux clump, and (3) the majority of events with an HMI-detectable neutral line show jet-like and loop-like structures, whereas weaker campfires, e.g, dot-like ones, are the majority of our campfire events having no HMI-detectable flux of either polarity. We conclude that if the no-magnetic-flux smaller campfires are similar to larger campfires in being small flare-like explosive releases of magnetic energy, the active magnetic field in them is too weak to be detected by HMI.
Student Name: Samuel Cathcart
Advisor Name: Dr. David Falconer (UAH CSPAR/NASA Marshall Space Flight Center)
Project Title: Improving the Forecasting of Space Weather by Improving MagPy
Project Description:
MagPy is a computer program which uses Helioseismic and Magnetic Imager (HMI) vector magnetograms to forecast major space weather events like major solar flares, coronal mass ejections (CMEs), and solar particle events (SPEs). MagPy is written in Python and is an upgraded version of the IDL computer program MAG4. From vector magnetograms, various free-energy proxies are calculated for solar active regions. These free-energy proxies are converted into predicted event rates for each active region. MagPy was improved by varying multiple thresholds to optimize forecast accuracy. This accuracy is measured by two different metrics, the True and Heidke Skill Scores (TSS and HSS). A one is a perfect score, and a zero means that a prediction cannot be accurately made. The thresholds used are 1)Smooth factor, 2)B Radial (Br) Magnitude, 3)Potential Field, and 4)Flux Br Magnitude Thresholds. We have investigated to determine if these optimal thresholds actually have an effect on the data resulting in it being optimized.
Student Name: Dakota Davis
Advisor Name: Dr. Joshua Wood (NASA Marshall Space Flight Center)
Project Title: Creating a Database of Pulse Waveforms for Scintillator-based Gamma-ray Detectors
Project Description:
The first Gamma-ray Burst (GRB) counterpart to a gravitational wave event, GRB 170817A, proved that monitoring for gamma-ray transients is an essential part of multi-messenger astronomy. As a result, research teams, globally, are now working towards the next generation of GRB instruments. To aid this work, we are creating a database of pulse waveforms for scintillation detectors over gamma-ray energies from 30- 1000 keV. This database will inform performance estimates, such as the minimum energy threshold and pulse shape discrimination ability in phoswich-style detectors. We will present initial results from the database using a Hamamatsu R12699 flat panel photomultiplier tube (PMT) coupled to NaI(Tl) and CsI(Na) scintillators.
Student Name: Makayla Frisse
Advisor Name: Dr. Mehmet Sarp Yalim (UAH/CSPAR)
Project Title: Investigating Ohmic Heating as a Solar Active Region Atmosphere Heating Mechanism
Project Description:
One of the most compelling questions in modern solar physics is the cause of the extreme heating of the solar atmosphere, which causes a temperature increase from about 5000 K in the photosphere to nearly 1 million K in the corona in just about 10,000 km. There are various mechanisms proposed to investigate this heating. In this work, we investigate Ohmic heating due to the dissipation of electric currents by magnetic resistivity, namely Cowling resistivity, as a heating mechanism of the lower solar atmosphere, namely the chromosphere. The plasma in the chromosphere is not fully ionized and ions and neutrals exist simultaneously. Cowling resistivity follows the interactions between ions and neutrals. We perform a data-constrained analysis to calculate the Ohmic heating rate in a solar active region atmosphere based on tabulated data of densities and temperature from five different semi-empirical solar atmosphere models, namely Maltby-M, VAL C, VAL F, Harvard-Smithsonian Reference Atmosphere, and Ding & Fang, in combination with the magnetic field calculated from the non-force-free field (NFFF) extrapolation technique applied to Solar Dynamics Observatory/Helioseismic and Magnetic Imager SHARP vector magnetogram data. We investigate the variations of Cowling resistivity and the associated Ohmic heating rate in the active region atmosphere (e.g., corresponding to NOAA AR 11166 on 2011-03-07T06:00:29 UT) based on the different atmosphere models and the temperature calculated from the inversion of spectral data from the Interferometric BIdimensional Spectropolarimeter (IBIS) instrument of the ground-based Dunn Solar Telescope (DST) and demonstrate that this heating mechanism can contribute to the heating of lower solar atmosphere in regions where electric currents are present. We also specifically show that the investigated Ohmic heating mechanism heats up a sunspot light bridge that occurs in the umbra of NOAA AR 12002 on 2014-03-13. We support the latter conclusion by calculating the enhancements of temperature and internal energy with respect to the umbral surroundings based on the inverted temperature data from DST/IBIS which show a good correlation with the current and the Ohmic heating rate, respectively.
Student Name: Frank Hutchison
Advisor Name: Dr. Sanjiv Tiwari (Lockheed Martin Solar and Astrophysics Laboratory)
Project Title: Solar Flares in Metastable Magnetic Arches
Project Description:
We present two GOES-class C1.5 confined (non-ejective-eruption) solar flares that occurred in a simple bipolar active region (AR) on separate days: 2013 June 19, 22. The observations are from the Solar Dynamics Observatory (SDO): transition-region and coronal UV and EUV images from SDO’s Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms from SDO’s Helioseismic and Magnetic Imager. It appears that this AR’s magnetic field had the overall form of an arch having no sharp polarity inversion line or sheared-field filament and/or filament channel snaking through its core. No AR-spanning sigmoid field erupts to make either flare. In the UV and EUV images, the flare ribbons turn on suddenly, do not spread apart substantially, and do not grow much wider. The AR’s magnetic flux content shows no conspicuous rise or decline on the day of either flare. These results suggest that these confined flares might work quite differently than flares that fit the filament-eruption-based standard model for confined flares (e.g., Moore et al. 2001). We present a cartoon depicting a magnetic loop having left-handed magnetic twist surrounded by right-handed-twist field in a magnetic arch, supposedly metastable against reconnection. We conjecture this equilibrium configuration of opposite-twist arched field could be bumped/triggered to suddenly reconnect, thereby consuming the embedded opposite magnetic twist and heating a flare loop like those in our two flares.
Student Name: Matthew Ryan Joyner Jr.
Advisor Name: Dr. Lingling Zhao (UAH/Department of Space Science)
Project Title: Particle Injection at the Mediated Shock
Project Description:
Collisionless shock waves can produce energetic particles via diffusive shock acceleration (DSA). DSA theory dictates that seed particles, which have sufficient energy to cross the shock wave, gain energy by bouncing off turbulence upstream and downstream. Seed particles can be recognized as pre-accelerated thermal component, which exceed injection energy. The produced energetic particles can mediate the shock structure when the pressure of energetic particles (derived from fluid perspective) dominates over the thermal and magnetic pressure. The dominant energetic particle pressure can decelerate the incoming plasma flow, which leads to a modified shock structure profile with a smooth transition. Although it is rare, the modified shock has been observed in the heliosphere. As a result, the mediated shock transition region is usually broader than the non-mediated shock. Although It’s been discussed how thermal particles are injected at the standard non-mediated shock waves, the particle injection process is still unclear at the mediated shock waves. If the injection process at the mediated shock waves is less efficient to produce enough high energies, there could be no further acceleration by diffusive shock accelerations (DSA).
In this work, we perform a test particle simulation. In the simulation, the shock profile is given as a tangent hyperbolic function. The underlying Alfven turbulence upstream and downstream of the shock follows a Kolmogorov - 5/3 power spectrum. We vary the thickness of the shockwave to study the differences in particle behavior at the mediated shock and compare with the non-mediated shock. Specifically, we measure the energy distribution function of particles, to check how many particles exceed the injection energy. This serves as an important step for studying particle acceleration and transport by the mediated shock waves.
Student Name: Allison Knott
Advisor Name: Dr. Alphonse Sterling (NASA Marshall Space Flight Center)
Project Title: Exploring the Nature of Small-scale Eruptions that Make Coronal Jets in the Sun's Atmosphere
Project Description:
Solar coronal jets are transient (~10--20 min), narrowly collimated (~10,000 km wide and reaching ~50,000 km length) plasma outflows, frequently observed in X-rays and EUV, that originate in a bright jet-base location near the photosphere and extend in the form of a spire into the corona. Jet spires tend either to remain much narrower than the extent of the base, or to grow to be comparable to the size of that base. Moore et al. (2010, ApJ, 720, 757) called the X-ray-observed narrow- and wide-spire jets "standard" and "blowout" jets, respectively. Many, if not most or all, coronal jets result from miniflament eruptions (MFEs), which are a smaller-scale version of the filament eruptions that produce solar flares and initiate coronal mass ejections (Sterling et al. 2015, Nature, 523, 437). Analogous to the large-scale eruptions, MFEs can be either confined or ejective, based on whether the erupting minifilament stays largely confined to the jet’s base or erupts outward into the far corona. An early hypothesis was that standard jets result mainly from confined MFEs and blowout jets from ejective MFEs (Sterling et al. 2015). To test this idea, using SDO/AIA 171, 193, 211, and 304 Å images we looked at the 20 jets from 2010 studied by Sterling et. al. (2015), consisting of 14 blowout and 5 standard jets (one jet was uncertain). We found: for blowout jets, 7 originate from ejective MFEs, 2 from confined MFEs, and for the remaining 5 blowout jets it was unclear whether the MFE was confined or ejective. For the standard jets, we found one to originate from a confined MFE and 4 to be unclear. We conclude that there is not a strong correlation between narrow/wide X-ray-jet spire and whether the MFE is confined or ejective, and thus the dynamics of how spires are formed from MFEs may be more complex than originally presumed. Sterling et al. (2022, ApJ, 927, 127) reached a similar conclusion with a different set of jets.
Student Name: John Riley O’Toole
Advisor Name: Dr. Nikolai Pogorelov (UAH/Department of Space Science)
Project Title: Optimizing the Source Surface Height of an Empirical Coronal Model During Solar Cycle 23 Minimum Using Remote and In Situ Measurements
Project Description:
The Potential Field Source Surface (PFSS) model is a simple and effective method for approximating the coronal magnetic field. The model assumes electric currents in the corona are negligible and, at some distance from the sun, a spherical source surface exists where all the solar magnetic field lines are completely radial. Traditionally, the source surface height (radius) is taken to be at 2.5 solar radii. However, several studies argue that during periods of solar minimum, the source surface height may need to be lowered significantly to produce PFSS results that better match measured data at 1 AU. We build on those arguments by computing PFSS solutions for the solar cycle 23 minimum period using a high-performance finite difference solver called POT3D with magnetograph data from the Global Oscillation Network Group (GONG) for source surface heights varying from 1.5 to 3.0 solar radii. One of the tools we used for our analysis was the McIntosh Archive, which recently has been updated through solar cycle 23. This archive is a collection of digitized (originally hand-drawn) synoptic maps of the sun from Carrington Rotations 1487-2086 that, among many solar magnetic features, show coronal holes. The comparison of the model radial magnetic field strength with near-Earth measurements suggest that the optimum PFSS source surface height varies between 1.6 and 2.1 solar radii and is on average ~1.75 solar radii for Carrington Rotations 2066-2073 in 2008. Visual comparison of the PFSS model coronal hole maps with the McIntosh Archive synoptic maps and EUV images of the Sun also support our conclusion.
Student Name: Tucker Quering
Advisor Name: Dr. Vladimir Florinski (UAH/Department of Space Science)
Project Title: Development of Hybrid Plasma Simulations to Study Shock Waves Beyond the Solar System
Project Description:
In 2012, the Voyager 1 space probe left the solar system and began gathering the first ever in situ observations of plasma in the very local interstellar medium (VLISM). Since leaving the solar system, Voyager 1 has twice observed noticeable increases in the background magnetic field, observed on the scale of multiple days (Burlaga & Ness 2016). Some have hypothesized that these observations could be the result of a shock, although the increase in the magnetic field occurs on a much broader scale than is typical for a shock within the solar system. Since plasmas within the solar system are nearly always considered collisionless, we use hybrid plasma simulations to investigate whether weak Coulomb collisionality between ions could result in such a broad shock structure. We first discuss an explicit simulation method that we ultimately show to be unsuitable for our purposes, but which carries valuable lessons nonetheless. Then we propose a more promising semi-implicit simulation scheme and present preliminary results in its development.
This work was supported by the NSF award AGS-1950831. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Student Name: Christina Tarsitano
Advisor Name: Dr. Subramania Athiray Panchapakesan (UAH/CSPAR)
Project Title: Evolution of Solar Active Regions Observed by MaGIXS-1 Sounding Rocket Flight
Project Description:
The first rocket flight of the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS-1) was successfully launched on 30 Jul 2021. MaGIXS-1 observed portions of two active regions 12846 and 12847 for about 300 sec from 18:23 to 18:28 UT. We studied these two active regions using SDO/AIA data from July 28, 2021 to July 31, 2021 to understand how temperature evolves with time. We evaluated two bright points in active region 12846 and the bright areas of active region 12847. For this task, we considered 30 minute interval data sets at the following times (i) 48 hours before launch, (ii) 24 hours before launch, (iii) 6 hours before launch, (iv) at the time of MaGIXS-1 launch, and (v) 6 hours after launch. First, we compiled movies of different time interval data sets to understand what time brightenings occurred at different AIA filter channels. By using a mask of bright pixels, we made intensity (DN/pixel) light curves to understand if the brightenings shown on the light curve appeared at the same time as the movie. Then we derived Differential Emission Measure (DEM) maps using SPARSE DEM inversion and determined the evolution of DEM weighted temperature. Light curves that showed a steady intensity and movies that showed steady brightenings had a DEM Temperature of 2-3 MK, while movies that showed rapid brightenings and the light curves showed spikes of intensity had a DEM Temperature that reached between 3-4 MK. Here, we will present our findings on the temperature evolution of these active regions and discuss how it compares/supports the inferences from MaGIXS-1 observations.
