Automatic detection of white-light flare kernels in SDO/HMI intensitygrams

Mravcová, Lucia; Švanda, Michal

doi:10.1016/j.newast.2017.06.003

Cited by 8 publications

(7 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Considering that the flare heating, in particular by electron beam bombardment as assumed in our simulations, is impulsive with always a short duration, our results provide a possible explanation that, at least some, if not all, of the magnetic transients observed in solar flares are flare-induced artifacts. It should be noticed that some previous observations of magnetic transients associated with flares showed similar enhancement and blue asymmetry of this line (Sun et al 2017), and sometimes an emission peak in the line center (Maurya et al 2012;Mravcová & Švanda 2017). Yet we would like to point out that the HMI spectral resolution can attenuate the intensity enhancement at the line center.…”

Section: Discussion and Summarysupporting

confidence: 58%

Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

Hong

Ding

et al. 2018

ApJL

View full text Add to dashboard Cite

The Fe I 6173 Å line is widely used in the measurements of vector magnetic fields by instruments including the Helioseismic and Magnetic Imager (HMI). We perform non-local thermodynamic equilibrium calculations of this line based on radiative hydrodynamic simulations in a flaring atmosphere. We employ both a quiet-Sun atmosphere and a penumbral atmosphere as the initial one in our simulations. We find that, in the quiet-Sun atmosphere, the line center is obviously enhanced during an intermediate flare. The enhanced emission is contributed from both radiative backwarming in the photosphere and particle beam heating in the lower chromosphere. A blue asymmetry of the line profile also appears due to an upward mass motion in the lower chromosphere. If we take a penumbral atmosphere as the initial atmosphere, the line has a more significant response to the flare heating, showing a central emission and an obvious asymmetry. The low spectral resolution of HMI would indicate some loss of information but the enhancement and line asymmetry are still kept. By calculating polarized line profiles, we find that the Stokes I and V profiles can be altered as a result of flare heating. Thus the distortion of this line has a crucial influence on the magnetic field measured from this line, and one should be cautious in interpreting the magnetic transients observed frequently in solar flares.

show abstract

Section: Discussion and Summarysupporting

confidence: 58%

Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

Hong

Ding

et al. 2018

ApJL

View full text Add to dashboard Cite

show abstract

“…where E 2 is the irradiance measured by the channel 2 of LYRA, d is the Sun-Earth distance, C 2 is the calibration coefficient of the channel 2, S 2 is the effective area of channel 2. A is the emitting area estimated using the method by Mravcová & Švanda (2017) to be 240 Mm 2 at 11:58 UT (the peak time in LYRA channel 2) based on the SDO/HMI observations of the flare in the wing of the Fe I 6173 Å line (M. Švanda, private communication).…”

Section: Spectral Modelingmentioning

confidence: 99%

First Detection of Solar Flare Emission in Mid-ultraviolet Balmer Continuum

Dominique

Zhukov

Heinzel

et al. 2018

ApJL

View full text Add to dashboard Cite

We present the first detection of solar flare emission at middle-ultraviolet wavelengths around 2000Å by the channel 2 of the Large-Yield RAdiometer (LYRA) onboard the PROBA2 mission. The flare (SOL20170906) was also observed in the channel 1 of LYRA centered at the H I Lyman-α line at 1216Å, showing a clear non-thermal profile in both channels. The flare radiation in channel 2 is consistent with the hydrogen Balmer continuum emission produced by an optically thin chromospheric slab heated up to 10000 K. Simultaneous observations in channels 1 and 2 allow the separation of the line emission (primarily from the Lyman-α line) from the Balmer continuum emission. Together with the recent detection of the Balmer continuum emission in the near-ultraviolet by IRIS, the LYRA observations strengthen the interpretation of broadband flare emission as the hydrogen recombination continua originating in the chromosphere.

show abstract

“…They occur at a huge range of energies and spatial scales, and large events occur less frequently than smaller flares. Fitting the energy distribution of observed small-scale brightenings to a power law provides an estimate of the energy available at unresolved scales (Crosby, Aschwanden, and Dennis, 1993;Hudson, 1991;Lu and Hamilton, 1991) and may give constraints on heating mechanisms. However, published results give a range of power laws which are inconclusive (Vilangot Nhalil et al, 2020;Aschwanden and Parnell, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Sekse, Rouppe van der Voort, and De Pontieu (2012) attempt to determine whether events in neighbouring frames belong to the same chain of events based on a frame-by-frame pixel density overlap. Work has also been done with filtering long-time intensity trends from detections in order to determine the true brightness of white-light flares (Mravcová and Švanda, 2017), running central median methods for resolving fine-scale dynamics (Plowman, 2016), and the inference of background data and other properties from small boxes/cubes surrounding each brightening (Nelson et al, 2017a). There are few instances of comprehensive, homogeneous multi-instrument studies of small-scale structures/events conducted over very large data sets, that encompass and distinguish large regions of the chromosphere/corona.…”

Section: Introductionmentioning

confidence: 99%

Detecting and Characterising Small-Scale Brightenings in Solar Imaging Data

2021

View full text Add to dashboard Cite

Observations of small-scale brightenings in the low solar atmosphere can provide valuable constraints on possible heating and heat transport mechanisms. We present a method for the detection and analysis of brightenings, and demonstrate its application to time-series imagery of the Interface Region Imaging Spectrograph (IRIS) in the extreme ultraviolet (EUV). The method is based on spatio-temporal band-pass filtering, adaptive thresholding and centroid tracking, and records an event’s spatial position, duration, total brightness and maximum brightness. Spatial area, brightness, and position are also recorded as functions of time throughout the event’s lifetime. Detected brightenings can fragment, or merge, over time – thus the number of distinct regions constituting a brightening event is recorded over time, and the maximum number of regions recorded as $N_{\mathit{frag}}$ N frag , which is a simple measure of an event’s coherence or spatial complexity. A test is made on a synthetic datacube composed of a static background based on IRIS data, Poisson noise and $\approx 10^{4}$ ≈ 10 4 randomly-distributed, moving, small-scale Gaussian brightenings. Maximum brightness, total brightness, area, and duration follow power-law distributions, and the results show the range over which the method can successfully extract information. The test shows that the recorded maximum brightness of an event is a reliable measure for the brightest and most accurately detected events, with an error of 6%. Event area, duration and speed are generally underestimated by around 15% and have an uncertainty of 20–30%. The total brightness is underestimated by 30%, and has an uncertainty of 30%. Applying this detection method to real IRIS quiet-sun data spanning 19 minutes over a $54.40''\times 55.23''$ 54.40 ″ × 55.23 ″ field of view (FOV) yields 2997 detections, 1340 of these detections either remain un-fragmented or fragment to two distinct regions at least once during their lifetime ($N_{\mathit{frag}}\le 2$ N frag ≤ 2 ), equating to an event density of $3.96\times 10^{-4}$ 3.96 × 10 − 4 arcsec−2 s−1. The method will be used for a future large-scale statistical analysis of several quiet-sun (QS) data sets from IRIS, other EUV imagers, and other types of data including H$\alpha $ α and visible photospheric imagery.

show abstract

Automatic detection of white-light flare kernels in SDO/HMI intensitygrams

Cited by 8 publications

References 42 publications

Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

First Detection of Solar Flare Emission in Mid-ultraviolet Balmer Continuum

Detecting and Characterising Small-Scale Brightenings in Solar Imaging Data

Contact Info

Product

Resources

About