Predicting the corona for the 21 August 2017 total solar eclipse


The total solar eclipse that occurred on 21 August 2017 across the United States provided an opportunity to test a magnetohydrodynamic model of the solar corona driven by measured magnetic fields. We used a new heating model based on the dissipation of Alfvén waves, and a new energization mechanism to twist the magnetic field in filament channels. We predicted what the corona would look like one week before the eclipse. Here, we describe how this prediction was accomplished, and show that it compared favourably with observations of the eclipse in white light and extreme ultraviolet. The model allows us to understand the relationship of observed features, including streamers, coronal holes, prominences, polar plumes and thin rays, to the magnetic field. We show that the discrepancies between the model and observations arise from limitations in our ability to observe the Sun’s magnetic field. Predictions of this kind provide opportunities to improve the models, forging the path to improved space weather prediction.

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Fig. 1: Comparison between the observed and predicted eclipse corona for the 21 August 2017 total solar eclipse.
Fig. 2: Comparison between observed and predicted EUV emission.
Fig. 3: Investigating the origin of equatorial rays.
Fig. 4: Comparison between observed features and model predictions.
Fig. 5: Polarity inversion line (PIL) comparison on 14 August 2017.


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This research was supported by NASA (HSR and LWS programs), AFOSR and the National Science Foundation (NSF). Z.M. acknowledges support from NASA grants NNX16AH03G and NNX15AB65G. Computations were provided by NASA’s Advanced Supercomputing Division, NSF’s Texas Advanced Computing Center and San Diego Supercomputer Center. Data courtesy of NASA/SDO and the AIA and HMI science teams. We thank the International Space Science Institute in Bern, Switzerland, for hosting a team on ‘Global Non-Potential Magnetic Models of the Solar Corona’, led by A. Yeates, where some of the ideas were developed. We thank the Solar Physics Group at Stanford University for their support in providing timely access to HMI data. Data courtesy of the Mauna Loa Solar Observatory, operated by the High Altitude Observatory (HAO), as part of the National Center for Atmospheric Research (NCAR). NCAR is supported by the NSF. D.H.M. thanks both the UK STFC and the Leverhulme Trust for their financial support. L.A.U. was supported by the NSF Atmospheric and Geospace Sciences Postdoctoral Research Fellowship Program (Award AGS-1624438) and is hosted by HAO at NCAR. The Williams College Eclipse Expedition was supported in large part by grants from the Solar Terrestrial Program of the Division of Atmospheric and Geospace Sciences of the NSF (Award AGS-1602461) and from the Committee for Research and Exploration of the National Geographic Society (Grant 9878-16), with additional support from the NASA Massachusetts Space Grant Consortium, the Sigma Xi scientific research honor society and the Clare Booth Luce Foundation.

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Z.M. and C.D. wrote the text, developed and ran the MHD model, and analysed the output. R.M.C. developed and ran the MHD model. D.H.M. ran the magnetofrictional model. L.A.U. analysed data and provided model inputs. J.A.L., P.R., R.L., T.T. and V.S.T. contributed to the development of the MHD model. J.W., P.R. and Z.M. developed the website. M.D. photographed the eclipse and produced an eclipse image. J.M.P. organized the 2017 eclipse expedition and its imaging, supervised the composition of an eclipse image, and contributed to the text. W.C. composed an eclipse image. All authors reviewed the manuscript.

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Correspondence to Zoran Mikić.

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Mikić, Z., Downs, C., Linker, J.A. et al. Predicting the corona for the 21 August 2017 total solar eclipse. Nat Astron 2, 913–921 (2018).

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