Bulletin of the American Physical Society
2017 Annual Meeting of the APS Mid-Atlantic Section
Volume 62, Number 19
Friday–Sunday, November 3–5, 2017; Newark, New Jersey
Session H5: Astr II: Solar Tomography |
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Chair: Maria Kazachenko, Berkeley Room: Atrium, Campus Center, NJIT |
Saturday, November 4, 2017 2:00PM - 2:12PM |
H5.00001: Solar Tomography: current progress and future perspectives Gregory Fleishman Solar activity is driven by solar magnetism. All essential dynamic processes underlying the solar activity, such as magnetic reconnection, particle acceleration, and eruptions are fundamentally three-dimensional (3D). In contrast, what we observe using modern ground- and space- based observatories are 2D projections taken out of the 3D reality. Thus, the challenge the modern solar physics sees is how to reconstruct the 3D reality out of those 2D projections. In this presentation I briefly review the approaches to address this challenge with the data and modeling tools we have now and anticipate to have in near future. In particular, I am going to emphasize the role of the imaging spectroscopy and specropolarimetry in the microwave and millimeter domains from such instruments as Expanded Owens Valley Array and Atacama Large Millimeter/submillimeter Array. [Preview Abstract] |
Saturday, November 4, 2017 2:12PM - 2:48PM |
H5.00002: GX Simulator: A highly interactive 3D modeling tool for studying solar flares and active regions Invited Speaker: Gelu Nita Study of solar active regions and flaring loops requires analysis of imaging data obtained in multiple wavelength domains with differing spatial resolution, in a framework supplied by advanced 3D physical models. To facilitate such studies, we have developed our simulation package, GX Simulator, which we maintain, continuously enhance, and distribute through the SolarSoft repository, (ftp://sohoftp.nascom.nasa.gov/solarsoft/packages/GX Simulator/). The object-based architecture of the GX Simulator, which runs on Windows, Mac, and Unix platforms, offers important capabilities, including the abilities to import 3D density and temperature distribution models, or to assign to each individual voxel numerically defined Differential Emission Measure distributions; to apply parametric heating models involving average properties of the magnetic field lines crossing a given voxel volume; to create magnetic flux tubes and populate them with user-defined non-uniform thermal plasma and anisotropic, non-uniform, nonthermal electron distributions; to compute and investigate the spatial and spectral properties of radio, EUV, and X-ray emission calculated from the model, and to compare the model-derived images and spectra with observational data. [Preview Abstract] |
Saturday, November 4, 2017 2:48PM - 3:00PM |
H5.00003: IDL Implementation of the Fast Gyrosynchotron Codes Alice Gao, Zachary Breit, Jason Wong, Alexey Kuznetsov, Gelu Nita, Gregory Fleishman Fast Gyrosynchotron Codes in GX\textunderscore Simulator were originally written in Fortran and C$++$ and could only be executed using operating system-dependent executables. In the first step for future compatibility across operating-systems, Fast Codes was rewritten in IDL. It was done without referencing the original code in Fortran and C$++$ to allow for optimal calculations and program speed inside IDL. All the functions were first written as they appeared on paper into the program; then they were then changed to the proper 1D array or 2D array and proper matrix multiplication was then implemented in the program. All of the data was stored in arrays because for loops had to be avoided since they slow down calculations in IDL. As a result, after Fast Codes was properly implemented, much of the optimizing involved fixing matrix operations so they would be more efficient. The output of Fast Codes plotted intensity values calculated from IDL against the original executables from Fortran. Different parameters were then tested to see the functionality of the IDL program underneath different circumstances. It was discovered that the program did not work too well with extremely low temperatures. Fast Gyrosynchotron Codes was then included in the official update of GX\textunderscore Simulator later that year. [Preview Abstract] |
Saturday, November 4, 2017 3:00PM - 3:12PM |
H5.00004: Platform-independent radio radiation transfer codes for GX Simulator. Zachary Breit, Alice Gao, Alexey Kuznetsov, Gelu Nita, Gregory Fleishman GX\textunderscore Simulator, a solar modeling tool developed in the Interactive Data Language (IDL), relies on fast radio radiation transfer codes implemented as system-dependent executables (DLLs). Although the Fast Gyrosynchrotron Codes (FGCs) were already implemented in IDL to calculate intensities for a single volume element, they could not perform the radiation transfer calculations to find intensity along a line of sight. Here we report the implementation of the radio radiation transfer codes developed in IDL, optimized using matrix operations, and tested against the original executables, which provide independence on the operating system. In order to improve performance, the functionality of the FGCs was enhanced to match that of the original programs. In particular, four energy distributions and five pitch angle distributions were programmed and tested. Once the remaining distributions are implemented and tested, the IDL radiation transfer programs will be mature to be implemented into the official GX\textunderscore Simulator release. [Preview Abstract] |
Saturday, November 4, 2017 3:12PM - 3:24PM |
H5.00005: Three-dimensional forward-fit modeling of the hard X-ray and the microwave emissions of the 2015-06-22 M6.5 flare Natsuha Kuroda, Dale Gary, Haimin Wang, Gregory Fleishman, Gelu Nita, Ju Jing The well-established notion of a "common population" of the flare-accelerated electrons simultaneously producing the hard X-ray (HXR) and the microwave (MW) emission has been challenged by some studies reporting the discrepancies between the HXR-inferred and the MW-inferred electron energy spectra. The traditional methods of their spectral inversion have some problems that can be mainly attributed to the unrealistic and the oversimplified treatment of the flare emission. To properly address this problem, we use a Non-linear Force Free Field model extrapolated from an observed photospheric magnetogram as input to the three-dimensional, multi-wavelength modeling platform GX Simulator, and create a unified electron population model that can simultaneously reproduce the observed HXR and MW observations. We model the end of the impulsive phase of the 2015-06-22 M6.5 flare, and constrain the model using observations made by the Reuven Ramaty High Energy Solar Spectroscopic Imager (HXR) and the Expanded Owens Valley Solar Array (MW). Our results reveal that an "HXR invisible" population of nonthermal electrons may be trapped in a large volume of magnetic field above the HXR-emitting loops, which is observable by its gyrosynchrotron radiation emitting mainly in MW low frequency range. [Preview Abstract] |
Saturday, November 4, 2017 3:24PM - 3:36PM |
H5.00006: Nonthermal electron evolution in 3D at the rise phase of a 2002-04-12 dense solar flare. Kevin Tong, Zhizhuo Zhou, Natsuha Kuroda, Gelu Nita, Gregory Fleishman Utilizing the three-dimensional, multi-wavelength modeling platform GX Simulator, we modeled the nonthermal electron evolution of the rise phase of the 2002-04-12 dense solar flare using observations made by the Owens Valley Solar Array (OVSA). The resulting model reveals several overarching trends in the progression of the flare, with the loop gradually increasing in radius as the flare approaches peak intensity and nonthermal electron density rising before every incremental increase in the loop's volume. [Preview Abstract] |
Saturday, November 4, 2017 3:36PM - 3:48PM |
H5.00007: Results from GX Fitting 12 April 2002 Flare Richard Wen, Sabina Jia, Natsuha Kuroda, Gelu Nita, Gregory Fleishman A solar flare is a transient, dynamic phenomenon. The variation of electromagnetic emission during a solar flare tells us about variation of the relevant physical parameters in the flare. Here we report an evolving 3D flare model for a flare on April 12, 2002. This model was created with the modeling software GX Simulator by adjusting physical parameters in the flaring loop to fit four minutes of microwave spectra measured by the Owens Valley Solar Array. In the fitting of the data, the spatial distribution of nonthermal electrons was primarily modified, but the energy distribution was also altered, specifically following the peak flare intensity. We found that the spatial distribution of the nonthermal electron increased its peak, cross-section, and width along the loop length as the flare increased in intensity. After the peak, the total number of nonthermal electrons decreased and minimum electron energy increased as the loop decreased in thickness. [Preview Abstract] |
Saturday, November 4, 2017 3:48PM - 4:00PM |
H5.00008: Nonthermal electron evolution in 3D at the main phase of a 2015-06-22 M-class solar flare Sabina Jia, Richard Wen, Natsuha Kuroda, Gelu Nita, Gregory Fleishman Solar flares release energy rapidly, accelerating electrons that travel along magnetic field lines and heat up the surrounding plasma. These electrons are known as nonthermal electrons, and to study their evolution across the duration of a solar flare, we model the main phase of the 2015-06-22 M-class solar flare using GX simulator, an interactive application developed for IDL that can model in three dimensions and across multiple wavelengths. The model is achieved by adjusting parameters relating to nonthermal electron distribution and density, along with the maximum energy of the flare. Our results reveal that overall, nonthermal electron density decreases while the electron cloud moves toward a larger magnetic field, indicating a general trend that the parameters, and consequently the evolution of the nonthermal electrons as well, follow as the flare progresses. [Preview Abstract] |
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