2016/11/09 by J. T. Schmelz, G. M. Christian, R. A. Chastain
Earth and Planetary Sciences · Physics and Astronomy · #Coronal loop #Earthquake Detection and Analysis #Ionosphere and magnetosphere dynamics #Isothermal process #Loop (graph theory) #Loop-mediated isothermal amplification #Magnetohydrodynamics #Plasma #Solar and Space Plasma Dynamics #Substructure #Work (physics) #astro-ph.SR
paper · pdf · doi:10.3847/0004-637x/831/2/199
published as ApJ, 831, 199 (2016)
openalex publication_date 2016/11/09 · openalex created_date 2016/11/30 · arxiv created 2017/05/25 · arxiv updated 2017/05/29 · openalex updated_date 2026/08/05
ABSTRACT We have expanded upon earlier work that investigates the relative importance of coronal loops with isothermal versus multithermal cross-field temperature distributions. These results are important for determining if loops have substructure in the form of unresolved magnetic strands. We have increased the number of loops targeted for temperature analysis from 19 to 207 with the addition of 188 new loops from multiple regions. We selected all loop segments visible in the 171 Å images of the Atmospheric Imaging Assembly (AIA) that had a clean background. Eighty-six of the new loops were rejected because they could not be reliably separated from the background in other AIA filters. Sixty-one loops required multithermal models to reproduce the observations. Twenty-eight loops were effectively isothermal, that is, the plasma emission to which AIA is sensitive could not be distinguished from isothermal emission, within uncertainties. Ten loops were isothermal. Also, part of our inventory was one small flaring loop, one very cool loop whose temperature distribution could not be constrained by the AIA data, and one loop with inconclusive results. Our survey can confirm an unexpected result from the pilot study: we found no isothermal loop segments where we could properly use the 171-to-193 ratio method, which would be similar to the analysis done for many loops observed with TRACE and EIT. We recommend caution to observers who assume the loop plasma is isothermal, and hope that these results will influence the direction of coronal heating models and the effort modelers spend on various heating scenarios.