The Sun's Dynamic Extended Corona Observed in Extreme Ultraviolet |
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Dan Seaton Submitted: 2021-05-20 16:58
The "middle corona" is a critical transition between the highly disparate physical regimes of the lower and outer solar corona. Nonetheless, it remains poorly understood due to the difficulty of observing this faint region (1.5-3 solar radii). New observations from the GOES Solar Ultraviolet Imager in August and September 2018 provide the first comprehensive look at this region's characteristics and long-term evolution in extreme ultraviolet (EUV). Our analysis shows that the dominant emission mechanism here is resonant scattering rather than collisional excitation, consistent with recent model predictions. Our observations highlight that solar wind structures in the heliosphere originate from complex dynamics manifesting in the middle corona that do not occur at lower heights. These data emphasize that low-coronal phenomena can be strongly influenced by inflows from above, not only by photospheric motion, a factor largely overlooked in current models of coronal evolution. This study reveals the full kinematic profile of the initiation of several coronal mass ejections, filling a crucial observational gap that has hindered understanding of the origins of solar eruptions. These new data uniquely demonstrate how EUV observations of the middle corona provide strong new constraints on models seeking to unify the corona and heliosphere.
Authors: Daniel B. Seaton, J. Marcus Hughes, Sivakumara K. Tadikonda, Amir Caspi, Craig DeForest, Alexander Krimchansky, Neal E. Hurlburt, Ralph Seguin, Gregory Slater
Projects: GOES/SUVI,SoHO-LASCO
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Publication Status: Accepted for publication in Nature Astronomy
Last Modified: 2021-05-23 10:47
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Real-time solar image classification: assessing spectral, pixel-based approaches |
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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
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Publication Status: In press, Journal of Space Weather and Space Clmate
Last Modified: 2019-10-02 13:04
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Solar signatures and eruption mechanism of the 2010 August 14 CME |
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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
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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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