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A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory
NTRS Full-Text: Click to View  [PDF Size: 7.2 MB]
External Online Source: doi:10.3847/1538-4357/aa7137
Author and Affiliation:
Viall, Nicholeen M.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Klimchuk, James A.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Abstract: In this paper, we examine 15 different active regions (ARs) observed with the Solar Dynamics Observatory and analyze their nanoflare properties. We have recently developed a technique that systematically identifies and measures plasma temperature dynamics by computing time lags between light curves. The time lag method tests whether the plasma is maintained at a steady temperature, or if it is dynamic, undergoing heating and cooling cycles. An important aspect of our technique is that it analyzes both observationally distinct coronal loops as well as the much more prevalent diffuse emission between them. We find that the widespread cooling reported previously for NOAA AR 11082 is a generic property of all ARs. The results are consistent with impulsive nanoflare heating followed by slower cooling. Only occasionally, however, is there full cooling from above 7 megakelvins to well below 1 megakelvin. More often, the plasma cools to approximately 1-2 megakelvins before being reheated by another nanoflare. These same 15 ARs were first studied by Warren et al. We find that the degree of cooling is not well correlated with the reported slopes of the mission measure distribution. We also conclude that the Fe (sup XVIII)-emitting plasma that they measured is mostly in a state of cooling. These results support the idea that nanoflares have a distribution of energies and frequencies, with the average delay between successive events on an individual flux tube being comparable to the plasma cooling timescale.
Publication Date: Jun 20, 2017
Document ID:
20170011596
(Acquired Dec 14, 2017)
Subject Category: SOLAR PHYSICS
Report/Patent Number: GSFC-E-DAA-TN50084
Document Type: Journal Article
Publication Information: The Astrophysical Journal ; p. 108; (ISSN 2041-8205; e-ISSN 2041-8213); Volume 842; Issue 2
Publisher Information: IOP
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 14p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright; Work of the U.S. Government - Public use permitted
NASA Terms: NANOFLARES; PLASMA COOLING; PLASMA HEATING; PLASMA TEMPERATURE; CORONAL LOOPS; TIME LAG; SOLAR ACTIVITY; SOLAR DYNAMICS OBSERVATORY; MAGNETIC FLUX; SOLAR MAGNETIC FIELD; SOLAR TRANSITION REGION; PLASMAS (PHYSICS); ULTRAVIOLET TELESCOPES; ULTRAVIOLET ASTRONOMY
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