Can a Nanoflare Model of Extreme-ultraviolet Irradiances Describe the Heating of the Solar Corona?

Nanoflares, the basic units of impulsive energy release, may produce much of the solar background emission. Extrapolation of the energy frequency distribution of observed microflares, which follows a power law to lower energies, can give an estimation of the importance of nanoflares for heating the...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2012-01, Vol.744 (2), p.113-11
Main Authors: Tajfirouze, E, Safari, H
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Computer simulation
COMPUTERIZED SIMULATION
Emission
Exponents
EXTRAPOLATION
EXTREME ULTRAVIOLET RADIATION
Flares
Heating
Mathematical models
Nanostructure
PHOTON EMISSION
Radiance
RADIANT FLUX DENSITY
RANDOMNESS
SOLAR CORONA
SUN
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Summary:Nanoflares, the basic units of impulsive energy release, may produce much of the solar background emission. Extrapolation of the energy frequency distribution of observed microflares, which follows a power law to lower energies, can give an estimation of the importance of nanoflares for heating the solar corona. If the power-law index is greater than 2, then the nanoflare contribution is dominant. We model a time series of extreme-ultraviolet emission radiance as random flares with a power-law exponent of the flare event distribution. The model is based on three key parameters: the flare rate, the flare duration, and the power-law exponent of the flare intensity frequency distribution. We use this model to simulate emission line radiance detected in 171 A, observed by Solar Terrestrial Relation Observatory/Extreme-Ultraviolet Imager and Solar Dynamics Observatory/Atmospheric Imaging Assembly. The observed light curves are matched with simulated light curves using an Artificial Neural Network, and the parameter values are determined across the active region, quiet Sun, and coronal hole. The damping rate of nanoflares is compared with the radiative losses cooling time. The effect of background emission, data cadence, and network sensitivity on the key parameters of the model is studied. Most of the observed light curves have a power-law exponent, [alpha], greater than the critical value 2. At these sites, nanoflare heating could be significant.
ISSN:0004-637X
2041-8205
1538-4357
2041-8213
DOI:10.1088/0004-637X/744/2/113