Student Name: Hayden Victor Dauphin
Advisor Name: Dr. Biswajit Mondal (NASA Marshall Space Flight Center)
Project Title: Active Region Simulation with EBTEL
Project Description:
The temperature of the solar atmosphere counterintuitively increases from a few thousand Kelvin to well over one million Kelvin while moving away from the photosphere to the corona. This currently unexplained phenomenon is known as the Coronal Heating Problem. Since its discovery, multiple theories have been proposed to explain the strangely drastic heating. One of them is the nanoflare theory, and it was proposed on the basis of observed solar flares. Nanoflares are small-scale, impulsive heating events thought to be happening constantly in the corona. Here, we examine nanoflares as a possible heating mechanism in the bright EUV and X-ray structures of the corona, known as active regions (AR). We utilize the Enthalpy-Based Thermal Evolution of Loops code to simulate the emission of the coronal loops within AR NOAA 12846. The results are tested for varying heating parameters of the nanoflare events. Then, we compare the simulated results with the observed emissions using different AIA and XRT filters to determine which parameters best align with the data
Student Name: Jacqueline Aguilar-Delgado
Advisor Name: Dr. Sanjiv Tiwari (Bay Area Environmental Research Institute)
Project Title: An Exploration of Episodic Heating in a Solar Quiet Region Bright Coronal Loop
Project Description:
The main purpose of this project was to quantify a quiet-region bright coronal loop’s bursty heating relative to its steady heating. We hoped that aspect of the heating of this loop would give clues to the longstanding fundamental solar-astrophysics problem of how the Sun’s global corona is kept heated to mega-Kelvin temperatures. Our analysis of a quiet-region bright coronal loop is a follow-on to the similar analysis in the study of Tiwari et al. (2023, ApJ, 942, 2) of the variation of an active region’s AIA hot-94 Å emission (from 4 - 8 MK plasma) over 24 hours. We use 171 and 211 Å 3-minute-cadance images of the loop from the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) over 41 hours. From them, we make maps of the maximum, minimum, and average brightness in each pixel for each 3-minute step of a time window of width ranging from 41 hours down to 30 minutes, and obtain the loop’s luminosity in each 211 map and each 171 map. From that, we get the ratio of the loop’s luminosity in the maximum-brightness map to that in the average-brightness map and the ratio of the loop’s luminosity in the minimum-luminosity map to that in the average-brightness map for each time step of each running time window. We found our quiet-region bright loop’s behavior in 171 emission (from 0.6 MK plasma) and in 211 emission (from 2 MK plasma) during the 41 hour interval was similar to but less bursty than the active region’s behavior in hot-94 emission over the 24 hour interval. For the loop’s 171 and 211 emission, at least a tenth of the loop’s coronal heating is in 0.25 - 1 hour bursts and less than nine tenths is steady for an hour or more. For the active region’s hot-94 emission, at least two thirds of the luminosity is in 0.25 - 1 hour bursts and less than a third is steady for an hour or more. In addition, for our quiet-region loop, we found that a peak in 211 luminosity usually leads a corresponding peak in 171 luminosity by 0.25 - 1 hour. This suggests that the loop’s bursty coronal heating is in flare-like bursts that heat sub-strands of the loop initially to temperatures greater than 2 MK, and each newly heated hot sub-strand cools down first through 2 MK and then through 0.6 MK.
Student Name: Ayla Celeste Evans
Advisor Name: Dr. Navdeep Panesar (Lockheed Martin Solar and Astrophysics Laboratory)
Project Title: Scrutiny of the Feet of Twenty Jetlets in EUV Coronal Plumes for Minority-polarity Magnetic Flux
Project Description:
Coronal jets are magnetically channeled narrow eruptions of plasma into the solar corona. Most jets are made by minifilament eruptions that are prepared and triggered by cancellation of opposite-polarity magnetic flux (Panesar et al. 2016). Jetlets are small-scale jets, first found by Raouafi & Stenborg (2014) when studying the bases of coronal plumes. Later, Panesar et al. (2018) found that jetlets also occur during flux cancellation at the edges of magnetic network lanes far from plume bases. They found their jetlets to have average base widths of 4000 km, average lifetimes of 3 minutes, and average speeds of 70 km/s. Their results indicate that jetlets are miniature versions of larger coronal jets. Here, we analyzed 20 plume-base jetlets using coronal EUV imaged data from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and line-of-sight magnetograms from the SDO/Helioseismic and Magnetic Imager (HMI). The jetlets occurred at the (negative-polarity) bases of two plumes, each in a different coronal hole on the central disk. We made movies having the highest cadence possible – 12 s for AIA 171 Å images and 45 s for HMI magnetograms – to closely examine the evolution and polarity structure of the magnetic flux at the base of each jetlet and to estimate the jetlet’s duration. The average jetlet duration was about 7 minutes. We looked for evidence of minority-polarity (positive) flux at the base of each jetlet. When positive flux was discernible, we judged whether it was canceling. Three events have obvious canceling minority flux at the base of the jetlet, 16 possibly have canceling minority flux, and only one out of the 20 has no hint of minority flux. While it does not rule out any other scenario for jetlet production, this result is consistent with all plume-base and other network jetlets being prepared and triggered by magnetic flux cancellation, with the minority-polarity flux usually being too weak to be definitely detected by HMI.
Student Name: Corie Elle Guggemos
Advisor Name: Dr. Lingling Zhao (UAH/Department of Space Science)
Project Title: Analysis of Turbulence Characteristics During Switchback Deflections
Project Description:
Observations of magnetic field switchbacks by Parker Solar Probe have led to extensive discussions regarding their driving mechanism and subsequent effects on solar wind heating and acceleration. A proposed explanation for the origin of the switchbacks is the interchange reconnection process. In this work, we further investigate the spectrum of the reduced magnetic helicity, cross helicity, and residual energy during the switchbacks. A Morlet wavelet analysis was used to determine these quantities indicative of structure and wave characteristics. We find no significant correlation between normalized magnetic helicity enhancement and magnetic switchbacks, thereby suggesting that these structures are not locally generated helical structures. Comparisons with theoretical predictions from the interchange reconnection mechanism are under investigation, and preliminary results appear to support a solar origin for the event.
Student Name: Lucas Hadding
Advisor Name: Dr. Peter Veres (UAH/Department of Space Science)
Project Title: How Fast are Gamma-ray Bursts?
Project Description:
Gamma-ray bursts (GRBs) are some of the most powerful explosions in the universe, formed by the merger of two neutron stars or through the core-collapse of a massive star. They outshine all other gamma-ray sources since the big bang and can be divided into short and long bursts. Short bursts last less than 2 seconds while long bursts last more than 2 seconds. They are characterized by relativistic jets that are launched at the poles and can have black holes that reside in the center. The goal of this research is to use the minimum variability timescale to determine methods to calculate the radius of gamma-ray emission and the maximum allowed peak energy for GRBs. Additionally, the goal is to estimate a redshift for GRBs that have no recorded redshift, and use this to approximate a luminosity distance for GRBs.
Student Name: Li Novasao Loy
Advisor Name: Dr. Alphonse Sterling (NASA Marshall Space Flight Center)
Project Title: Inconspicuous Minifilament Eruptions as the Source of Conspicuous Extreme Ultraviolet (EUV) Outflows in the Solar Atmosphere
Project Description:
We used EUV images from the Atmospheric Imaging Assembly (AIA) and magnetograms from the Helioseismic and Magnetic Imager (HMI), both onboard the Solar Dynamics Observatory (SDO), to search for the low-solar-atmospheric sources of nine blueshifted outflow events found by the EUV (Extreme Ultraviolet) Imaging Spectrometer (EIS) onboard Hinode. Five events were in the northern polar region and four were near the equator. For seven of the events, we find eruptive activity consistent with a minifilament eruption occurring at the time and location of the observed blueshift event, while the remaining two events were too feeble for us to make a determination. These minifilament eruptions are similar to but feebler than those previously found to make coronal jets. In three cases, we identify a jet-like spire emanating from the minifilament-eruption region, while in the other six events such a spire is too faint to be detected or is absent. We find the erupting minifilaments to have lengths of ~9K km and proper motion speeds of ~30 km/s near their eruption onset time, values which are within size and velocity ranges found previously for obvious erupting minifilaments in the production of obvious jets. In one of these events we find evidence of a minifilament candidate that is too close to the background noise level to properly determine if it is the source of the EIS outflow, but if it is, it suggests that omnipresent dynamic features in the lower solar atmosphere may create outflows, conveying that this could be the source of the solar wind. For two of the low-latitude cases, HMI magnetograms show evidence of flux cancellation among weak magnetic flux patches at about the eruption onset time, again consistent with what has been found for many stronger coronal jets. The fluxes for the other two low-latitude events were too close to the magnetogram noise level for us to make a determination. Our observations support that hard-to-detect erupting minifilaments can make inconspicuous coronal jets that result in conspicuous coronal outflows seen by EIS, confirming an earlier study by Sterling et al. (2022, ApJ, 940, 85). We strengthen the conclusion of that study by finding evidence that cancellation of flux near HMI’s detection limit results in erupting minifilaments that produce inconspicuous jets and conspicuous EIS-detected coronal outflows.
Student Name: Lucien Mallett
Advisor Name: Dr. Athiray Panchapakesan (UAH/Department of Space Science)
Project Title: DEM Inversion Failures During Solar Flares
Project Description:
The Sun is hot. We want to know exactly how hot the Sun is, but this is hard because it's so far away. The only thing we can do is take pictures of it from space or from here at home. But it turns out that we actually can find out how hot the Sun is, using those pictures! We can take pictures where we only use one color of light. Hot things are brighter in some colors, and cold things are brighter in other colors. By figuring out how bright the Sun is in each color, we can find how hot the Sun is. Sometimes the Sun makes large flashes that we are interested in learning about. But these flashes are so bright that our pictures come out wrong, so we can't use them to find out how hot the flashes are. Also, the only reason we can find how hot the Sun is from its color is because we know what the Sun is made of and how fast stuff in the Sun is moving. We don't know what the flashes are made of exactly, or how fast the stuff in them is going. All of this means that we can't figure out how hot the flashes are. We looked at big flashes from several years ago to study these problems. We found out exactly when and where looking at the pictures in different colors doesn't work, and suggested some ideas on how to fix these problems.
Student Name: Pari B. Patel
Advisor Name: Dr. Vladimir Florinski (UAH/Department of Space Science)
Project Title: Reconstruction of Magnetic Structures from Spacecraft Data: A Test Study for Voyagers in the Heliosheath
Project Description:
This study presents a C++ code implementing the Grad-Shafranov equation for reconstructing two-dimensional coherent magnetic structures from single-spacecraft data. The code follows the approach of Hau and Sonnerup [1999], where they recovered magnetic field maps of magnetopause current layer crossings using AMPTE/IRM measurements. We validated our initial code by reproducing their benchmark results, accurately reconstructing the magnetic islands and X-line structures embedded within the magnetopause layer. Using real AMPTE magnetopause crossings data, we graphed the pressure, vector potential, and different axes of the magnetic field against each other to recreate the magnetopause crossings studied by Hau and Sonnerup. Numerical methods preprocess the data to provide the proper frame velocity, constraints, and higher resolution spatial increments along the spacecraft trajectory. The Grad-Shafranov equation demonstrates the mapping of plasma equilibrium and coherence structures by generating 2D magnetic field representations from single-spacecraft observations. Further application to Voyager 1's sparse heliosheath measurements has the potential to provide insights and enhance the restricted direct observations from this distant frontier region.
Student Name: Isaiah Elijah Keemar Sears
Advisor Name: Dr. Nikolai Pogorelov (UAH/Department of Space Science)
Project Title: Time-Dependent Evolution of Compressible Turbulence in the Heliosheath and the Very Local Interstellar Medium
Project Description:
NASA's Voyager 1 and 2 are the only operational spacecraft providing unique in situ data from the outer heliosphere and the local interstellar medium (LISM). Voyager’s magnetic field observations have provided evidence for the presence of a compressible turbulence cascade in the heliosphere's outermost layer, the inner heliosheath (IHS), and in the Very Local Interstellar Medium (VLISM). However, properties of turbulence in these regions are not yet fully understood. It remains unclear: (1) if turbulence is different in regions of opposite heliospheric magnetic field (HMF) polarity observed in the inner heliosheath (IHS), (2) how turbulence evolves over the solar cycle, and (3) the role turbulence plays in the observed profiles of the bulk plasma quantities, with increasing distance from the Sun. Turbulence in the IHS coexists with coherent structures such as pressure pulses, magnetic islands, and, possibly, shock waves. The overall goal of this study is to characterize the behavior of turbulence in the IHS and VLISM using Voyager in situ data of magnetic field and plasma. We investigate potential connections between the intensity of fine-scale MHD turbulence, and thermal SW quantities such as temperature, density, and speed. To do so, we have conducted a Partial Variance of Increments (PVI) analysis and coupled it with a cross correlation analysis. This allowed us to show both the temporal variations in the turbulence behavior and to seek cross correlations between fine scale (1-hour increments) magnetic field fluctuations and thermal plasma observations. For the first time, we highlight the existence of long-term variations in the intensity of small scale magnetic field turbulence in the IHS. We show that such changes are correlated with the changes in the thermal plasma speed, density, and temperature. We also show the existence of correlated peaks in the PVI of the magnetic field and local enhancements in the thermal plasma pressure and speed. In the VLISM, we find an increase in small scale turbulence intensity after mid 2018, which may be related to solar cycle effects, possibly associated with enhanced charge exchange between SW neutral atoms and interstellar ions.
Student Name: Brayden Arlen Sellers
Advisor Name: Dr. Mehmet Sarp Yalim (UAH/CSPAR)
Project Title: A Data-Constrained Analysis of Joule Heating as a Solar Active Region Atmosphere Heating Mechanism over a ‘Second’ Sunspot Light Bridge
Project Description:
The coronal heating problem causes investigation of the heating mechanisms of the chromosphere and corona, in which temperatures increase multiple orders of magnitude over a few thousand kilometers above the photosphere. A proposed mechanism for this dramatic increase in thermal activity in the chromosphere is Cowling heating, namely the Joule heating due to dissipation of electric currents perpendicular to the magnetic field lines by Cowling resistivity. We investigate the contribution of Cowling heating within the solar active region atmosphere corresponding to NOAA AR 12121 on 2014-07-27 from 14:02 to 17:58 UT, in particular over a sunspot light bridge (LB). We conducted a data-constrained analysis to calculate Cowling resistivity together with its associated heating rate for this LB using observational data, and tabulated data from theoretical and semi-empirical solar atmosphere models. The observational data that we used are magnetic field calculated from the application of non-force-free field (NFFF) extrapolation technique to Solar Dynamics Observatory/Helioseismic and Magnetic Imager SHARP vector magnetogram data, and temperature data computed from the inversion of spectroscopic data from Interface Region Imaging Spectrograph (IRIS). The remaining plasma parameters that we used in our analysis are obtained from tabulated data from solar atmospheric models, namely Maltby M, VAL C, VAL F, HSRA, and Ding & Fang. Analysis of this LB shows Cowling heating to heat this structure as well as the importance of constraining our data analysis by observational temperature data to represent the dynamic nature of heating accurately.
