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* News 04/04/20 * The archive is using a new backend database. This has thrown up a few SQL errors in the last few days. If you have any issues please email adavey@nso.edu with either the number of eprint you are trying to edit or a link to your preprint.

Real-time solar image classification: assessing spectral, pixel-based approaches  

Dan Seaton   Submitted: 2019-10-02 12:03

In order to utilize solar imagery for real-time feature identification and large-scale data science investigations of solar structures, we need maps of the Sun where phenomena, or themes, are labeled. Since solar imagers produce observations every few minutes, it is not feasible to label all images by hand. Here, we compare three machine learning algorithms performing solar image classification using extreme ultraviolet and Hydrogen α images: a maximum likelihood model assuming a single normal probability distribution for each theme from Rigler et al. (2012), a maximum-likelihood model with an underlying Gaussian mixtures distribution, and a random forest model. We create a small database of expert-labeled maps to train and test these algorithms. Due to the ambiguity between the labels created by different experts, a collaborative labeling is used to include all inputs. We find the random forest algorithm performs the best amongst the three algorithms. The advantages of this algorithm are best highlighted in: comparison of outputs to hand-drawn maps; response to short-term variability; and tracking long-term changes on the Sun. Our work indicates that the next generation of solar image classification algorithms would benefit significantly from using spatial structure recognition, compared to only using spectral, pixel-by-pixel brightness distributions.

Authors: J. Marcus Hughes, Vicki W. Hsu, Daniel B. Seaton, Hazel M. Bain, Jonathan M. Darnel, Larisza Krista
Projects: GOES/SUVI,GONG

Publication Status: In press, Journal of Space Weather and Space Clmate
Last Modified: 2019-10-02 13:04
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Coronal Imaging with the Solar UltraViolet Imager  

Dan Seaton   Submitted: 2019-01-25 10:48

We investigate the coronal imaging capabilities of the Solar UltraViolet Imager (SUVI) on the Geostationary Operational Environmental Satellite-R series spacecraft. Nominally Sun-pointed, SUVI provides solar images in six Extreme UltraViolet (EUV) wavelengths. On-orbit data indicated that SUVI had sufficient dynamic range and sensitivity to image the corona to the largest heights above the Sun to date while simultaneously imaging the Sun. We undertook a campaign to investigate the existence of the EUV signal well beyond the nominal Sun-centered imaging area of the solar EUV imagers. We off-pointed SUVI line-of-sight by almost one imaging area around the Sun. We present the details of the campaign conducted when the solar cycle is at near the minimum and some results that affirm the EUV presence to beyond three solar radii.

Authors: Sivakumara K. Tadikonda, Douglas C. Freesland, Robin R. Minor, Daniel B. Seaton, Gustave J. Comeyne, Alexander Krimchansky
Projects: GOES/SUVI

Publication Status: Accepted
Last Modified: 2019-01-25 13:08
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Reconnection in the Post-Impulsive Phase of Solar Flares  

Dan Seaton   Submitted: 2018-04-02 22:11

Using a recently developed analytical procedure, we determine the rate of magnetic reconnection in the "standard" model of eruptive solar flares. During the late phase, the neutral line is located near the lower tip of the reconnection current sheet, and the upper region of the current sheet is bifurcated into a pair of Petschek-type shocks. Despite the presence of these shocks, the reconnection rate remains slow if the resistivity is uniform and the flow is laminar. Fast reconnection is achieved only if there is some additional mechanism that can shorten the length of the diffusion region at the neutral line. Observations of plasma flows by the X-Ray Telescope (XRT) on Hinode imply that the diffusion region is in fact quite short. Two possible mechanisms for reducing the length of the diffusion region are localized resistivity and MHD turbulence.

Authors: Terry G. Forbes, Daniel B. Seaton, Katharine K. Reeves
Projects: None

Publication Status: Accepted to ApJ
Last Modified: 2018-04-04 12:18
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Observations of an Eruptive Solar Flare in the Extended EUV Solar Corona  

Dan Seaton   Submitted: 2017-12-21 21:34

We present observations of a powerful solar eruption, accompanied by an X8.2 solar flare, from NOAA Active Region 12673 on 2017 September 10 by the Solar Ultraviolet Imager (SUVI) on the GOES-16 spacecraft. SUVI is noteworthy for its relatively large field of view, which allows it to image solar phenomena to heights approaching 2 solar radii. These observations include the detection of an apparent current sheet associated with magnetic reconnection in the wake of the eruption and evidence of an extreme-ultraviolet wave at some of the largest heights ever reported. We discuss the acceleration of the nascent coronal mass ejection to approximately 2000 km s-1 at about 1.5 solar radii. We compare these observations with models of eruptions and eruption-related phenomena. We also describe the SUVI data and discuss how the scientific community can access SUVI observations of the event.

Authors: Daniel B. Seaton and Jonathan M. Darnel
Projects: GOES/SUVI

Publication Status: ApJL (In press)
Last Modified: 2018-01-03 11:41
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Solar signatures and eruption mechanism of the 2010 August 14 CME  

Dan Seaton   Submitted: 2017-02-06 13:45

On 2010 August 14, a wide-angled coronal mass ejection (CME) was observed. This solar eruption originated from a destabilized filament that connected two active regions and the unwinding of this filament gave the eruption an untwisting motion that drew the attention of many observers. In addition to the erupting filament and the associated CME, several other low-coronal signatures that typically indicate the occurrence of a solar eruption were associated to this event. However, contrary to what is expected, the fast CME (v>900 km s-1) was accompanied by only a weak C4.4 flare. We investigate the various eruption signatures that were observed for this event and focus on the kinematic evolution of the filament in order to determine its eruption mechanism. Had this solar eruption occurred just a few days earlier, it could have been a significant event for space weather. The risk to underestimate the strength of this eruption based solely on the C4.4 flare illustrates the need to include all eruption signatures in event analyses in order to obtain a complete picture of a solar eruption and assess its possible space weather impact.

Authors: Elke D'Huys, Daniel B. Seaton, Anik De Groof, David Berghmans, Stefaan Poedts
Projects: ACE,GOES X-rays,PROBA2/SWAP,SDO-AIA,SDO-HMI,SoHO-LASCO,STEREO

Publication Status: Accepted for publication in the Journal of Space Weather and Space Climate
Last Modified: 2017-02-07 23:56
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Abstracts by Author
Real-time solar image classification: assessing spectral, pixel-based approaches
Coronal Imaging with the Solar UltraViolet Imager
Reconnection in the Post-Impulsive Phase of Solar Flares
Observations of an Eruptive Solar Flare in the Extended EUV Solar Corona
Solar signatures and eruption mechanism of the 2010 August 14 CME

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