The second paper is from Anthony Pineci (arxiv.org/abs/2103.08887). We applied deep learning methods to infer AIA EUV He II 304 A intensity from SOLIS He I 10830 A equivalent width. EUV emission drives exoplanet atmosphere escape, but 1/6
can only be observed in space. On the other hand, the He I infrared line is physically associated the He II line, and is accessible from the ground. Its formation mechanism is complicated though, so a simple regression won’t work. 2/6
For example, filaments and coronal holes are both dark in He I. However only the former is dark in He II. The latter is bright! Also, ARs appear dark in He I and bright in He II. 3/6
We find a fully-convolutional neural network (FCN) combined with additional geometric input (distance from disk center and latitude) outperforms FCN alone. It also outperforms all variants of U-Net and Pixel-wise structures. 4/6
The data set is small (1211 image pairs). We used 0.6/0.2/0.2 for training/validation/testing. We were able to achieve 7% relative error for the disk integrated flux and 20% for pixel-wise values. The geometric information likely helps. 5/6
Interestingly, inferring He I from He II doesn’t work as well. We are missing the filaments entirely in the predicted He I image! Would other inputs help? That’s the next step. 6/6
Correction: filaments and ARs are both dark in He I. However only the former is dark in He II. The latter is bright! Also, coronal holes appear bright in He I and dark in He II. 3/6 🤯

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More from @xudong_sun

17 Mar
We have two student papers out on arXiv today! The first is from Anna Payne (arxiv.org/abs/2103.09087). We studied EUV dimming associated with flux emergence, which is termed “emerging dimming”. We used AIA and HMI data to probe its origin. 1/5
The dimming occurs only in 171 A, and coincides with brightening in 211 A. We performed DEM analysis on 18 events. The amount of sub-MK plasma decreases, and the 1-2 MK plasma increases. The changes are correlated over 8 orders of magnitude! 2/5
We also look at the magnetic fields. The quiet-Sun photospheric field in the dimming region doesn’t change much. However, a potential field model shows that they are now connected to the emerged active region. 3/5
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