Work

Three-dimensional Reconstruction of Coronal Plasma Properties from a Single Perspective

Year: 2021

Type: article

Abstract: Much of our understanding of the state of coronal plasmas comes from observations that are optically thin. This means that light travels freely through the corona without being materially affected by it, which allows it to be easily seen through, but also results in a line-of-sight degeneracy that has previously thwarted attempts to recover the three-dimensional structure of the coronal plasma. However, although the corona is disorganized in the line-of-sight direction, it is highly organized in the field-aligned direction. This paper demonstrates how to exploit this organization to resolve the line-of-sight degeneracy in the plasma properties using a suitable magnetic field structure. This allows, for the first time, the two-dimensional optically thin plasma observations to directly drive the three-dimensional plasma reconstruction throughout an entire active region (or larger). A preliminary investigation with a potential field is shown, finding a solution which clearly resembles the real solar data, even with a single perspective. The results indicate that there is ample information in the resulting residuals that can be used to refine the magnetic field structure, suggesting that these residuals can in turn be used to directly constrain the magnetic field extrapolations used in the reconstruction. The paper concludes with a discussion of how these residuals can in turn be used to directly drive the magnetic field extrapolations.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/ac2664

Author: Joseph Plowman

Institution: Southwest Research Institute

Language: English

Topic: Solar and Space Plasma Dynamics

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: bronze

Funder: National Aeronautics and Space Administration

Award: GOALS&OBJECTIVES: WE SEEK TO UNDERSTAND WHETHER THE 'NANOFLARE HYPOTHESIS CAN EXPLAIN CORONAL HEATING BY ANALYZING NEW HIGH QUALITY EMPIRICAL DATA AND BY UNDERSTANDING THOSE DATA USING BOTH THEORY AND FORWARD MODELING. DESPITE SEVERAL IMPORTANT STUDIES OVER THE PAST TWO DECADES IT IS NOT YET CLEAR WHETHER THE SMALLEST SCALE EVENTS DELIVER MORE OR LESS POWER TO THE CORONA THAN DO SOLAR FLARES THEMSELVES. THE NUMBER VS. ENERGY DISTRIBUTION OF ENERGETIC EVENTS IS A POWER LAW WHOSE EXPONENT IS TANTALIZINGLY CLOSE TO THE CRITICAL VALUE OF -2. EXACTLY WHERE THE EXPONENT LANDS HAS NOT BEEN CONCLUSIVELY DETERMINED HOWEVER AND THE POWER LAW MAY CHANGE AT THE SMALLEST SCALES (HERE NOISE EFFECTS DOMINATE EXISTING STUDIES SO THEORETICAL ESTIMATES HAVE EXTRAPOLATED FROM LARGER SCALES). WE WILL FOCUS ON THE DISTRIBUTIONS OF THE SMALLEST IMPULSIVE EVENTS VISIBLE WITH SDO/AIA WHICH OFFERS GREATLY IMPROVED SENSITIVITY CADENCE TEMPERATURE COVERAGE AND FOV COMPARED TO PRIOR WORK USING TRACE. THE PROPERTIES OF EACH DETECTED EVENT WILL BE CAREFULLY CATALOGUED USING DIFFERENTIAL EMISSION MEASURE (DEM) ANALYSIS TO INFER TEMPERATURES AND ENERGETICS. IN TANDEM WITH THE AIA DATA ANALYSIS WE WILL CARRY OUT 'SYNTHETIC DATA' ANALYSIS EXERCISES AND FORWARD FITTING USING THE EBTEL AND/OR HYDRAD NUMERICAL MODELS TO IDENTIFY AND CORRECT FOR SYSTEMATIC CROSS-SCALE BIAS IN THE DETECTION ALGORITHMS. OUR MODELING COMPONENT IS A CRITICAL INNOVATION BECAUSE IT ALLOWS US TO UNDERSTAND AND CORRECT SYSTEMATIC SAMPLING EFFECTS THAT COULD SKEW THE SMALL-SCALE TAIL OF THE DISTRIBUTION. THESE EFFECTS INCLUDE BOTH SAMPLING BIAS AND PHYSICAL EFFECTS THAT AFFECT DETECTABILITY OF INDIVIDUAL EVENTS.