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Title: A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory

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 MK to well below 1 MK. More often, the plasma cools to approximately 1–2 MK 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 emission measure distribution. We also conclude that the Fe xviii emitting plasma that they measured is mostly inmore » 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.« less

Authors:
;  [1]
  1. NASA Goddard Space Flight Center, Solar Physics Laboratory, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22663479
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 842; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; ATMOSPHERES; COMPARATIVE EVALUATIONS; DISTRIBUTION; ELECTRON TEMPERATURE; EMISSION; HEATING; ION TEMPERATURE; PLASMA; SOLAR FLARES; SUN; ULTRAVIOLET RADIATION; VISIBLE RADIATION

Citation Formats

Viall, Nicholeen M., and Klimchuk, James A. A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA7137.
Viall, Nicholeen M., & Klimchuk, James A. A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory. United States. doi:10.3847/1538-4357/AA7137.
Viall, Nicholeen M., and Klimchuk, James A. Tue . "A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory". United States. doi:10.3847/1538-4357/AA7137.
@article{osti_22663479,
title = {A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory},
author = {Viall, Nicholeen M. and Klimchuk, James A.},
abstractNote = {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 MK to well below 1 MK. More often, the plasma cools to approximately 1–2 MK 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 emission measure distribution. We also conclude that the Fe 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.},
doi = {10.3847/1538-4357/AA7137},
journal = {Astrophysical Journal},
number = 2,
volume = 842,
place = {United States},
year = {Tue Jun 20 00:00:00 EDT 2017},
month = {Tue Jun 20 00:00:00 EDT 2017}
}