Release of Accurate AI-generated Solar Farside Magnetograms

In this study, we have greatly improved AI-generated solar farside magnetograms from STEREO/EUVI observations than before. We have modified our previous deep learning model and configuration of input datasets to generate more realistic magnetograms. First our model, which is called pix2pixCC, uses an update loss function: that of pix2pixHD model and correlation coefficient values between the real and generated data. Second, we construct input datasets of our model: solar farside EUV observations together with frontside data pairs of EUV observations and magnetograms. We expect that the frontside data pairs provide the historic information of magnetic field polarity distributions. When we train and evaluate the model with frontside input and target datasets, the fronside pairs are replaced by the pairs that were recorded one Carrington rotation before. Our results show that the present model is much better than our previous model (Jeong et al. 2020, ApJ Letters) in view of several metrics. In addition, the AI-generated farside magnetograms produce consistent polar field strengths and magnetic field polarities with those of nearby frontside SDO/HMI magnetograms for solar cycles 24 and 25. Our AI-generated Solar Farside Magnetograms (AISFMs) are now publicly available on line. In addition, we present several application methods and results using AISFMs. We construct synchronic global magnetic field maps with SDO/HMI and AISF magnetograms, and extrapolate solar coronal magnetic fields from them. We show that our results are much more consistent with EUV observations than those of the conventional method. And we suggest several prospects to study global magnetic connectivity with multi-view point observations, e.g., STEREO, Parker Solar Probe, and Solar Orbiter. This work was supported by Institute for Information & communications Technology Promotion (IITP) grant funded by the Korea government (MSIP) (2018-0-01422, Study on analysis and prediction technique of solar flares).