TRANSITION REGION AND CHROMOSPHERIC SIGNATURES OF IMPULSIVE HEATING EVENTS. I. OBSERVATIONS

ABSTRACT We exploit the high spatial resolution and high cadence of the Interface Region Imaging Spectrograph (IRIS) to investigate the response of the transition region and chromosphere to energy deposition during a small flare. Simultaneous observations from the Reuven Ramaty High Energy Solar Spe...

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Bibliographic Details
Published in:The Astrophysical journal 2016-09, Vol.829 (1), p.35
Main Authors: Warren, Harry P., Reep, Jeffrey W., Crump, Nicholas A., Simões, Paulo J. A.
Format: Article
Language:English
Subjects:
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Atmospheric models
Bursts
CHROMOSPHERE
DISTRIBUTION
EMISSION
Emission lines
Emission measurements
ENERGY ABSORPTION
ENERGY LOSSES
EXTREME ULTRAVIOLET RADIATION
Filaments
Heating
HEATING RATE
HYDRODYNAMIC MODEL
Hydrodynamic models
Magnesium
ONE-DIMENSIONAL CALCULATIONS
Pixels
Power law
PRECIPITATION
RED SHIFT
Silicon
Solar energy
SPATIAL RESOLUTION
SPECTRA
SPECTROMETERS
SUN
Sun: corona
Sun: transition region
TAIL ELECTRONS
TELESCOPES
X RADIATION
X ray imagery
X ray telescopes
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Summary:ABSTRACT We exploit the high spatial resolution and high cadence of the Interface Region Imaging Spectrograph (IRIS) to investigate the response of the transition region and chromosphere to energy deposition during a small flare. Simultaneous observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager provide constraints on the energetic electrons precipitating into the flare footpoints, while observations of the X-Ray Telescope, Atmospheric Imaging Assembly, and Extreme Ultraviolet Imaging Spectrometer (EIS) allow us to measure the temperatures and emission measures from the resulting flare loops. We find clear evidence for heating over an extended period on the spatial scale of a single IRIS pixel. During the impulsive phase of this event, the intensities in each pixel for the Si iv 1402.770 , C ii 1334.535 , Mg ii 2796.354 , and O i 1355.598 emission lines are characterized by numerous small-scale bursts typically lasting 60 s or less. Redshifts are observed in Si iv, C ii, and Mg ii during the impulsive phase. Mg ii shows redshifts during the bursts and stationary emission at other times. The Si iv and C ii profiles, in contrast, are observed to be redshifted at all times during the impulsive phase. These persistent redshifts are a challenge for one-dimensional hydrodynamic models, which predict only short-duration downflows in response to impulsive heating. We conjecture that energy is being released on many small-scale filaments with a power-law distribution of heating rates.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/829/1/35