|Coronal Prediction for the August 21, 2017 Total Solar Eclipse|
|Polarized Brightness (Newkirk Filter)||Log Polarized Brightness (Unsharp Masked)|
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This is a preliminary prediction of the solar corona for the August 21, 2017 total solar eclipse. The above images show two versions of the predicted brightness of polarized white light in the corona. The left image shows an image processed to simulate what would be seen when using a "Newkirk" radially graded filter. The image on the right is the polarized brightness on a log scale, sharpened using an "Unsharp Mask" filter. These are two different attempts to approximate what the human eye might see during the solar eclipse.
The image below on the left shows a digital processing of the polarized brightness using a "Wavelet" filter to bring out the details in the image. The image on the right shows traces of selected magnetic field lines from the model. Additional details about the eclipse and our prediction model are given below.
|Polarized Brightness (Wavelet Filtered)||Magnetic Field Lines|
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These images are aligned so that terrestrial (geocentric) north is up. This is the view of the Sun that would be seen by an observer on Earth with a camera aligned so that vertical is toward the Earth's north pole. In the magnetic field line image, the Sun's surface shows the intensity of the radial component of the photospheric magnetic field. The brightest colors show the location of active regions (strong magnetic fields). Images in a coordinate system aligned with solar north are also available.
On August 21, 2017, a total eclipse of the Sun will be visible across the entire contiguous United States. It will trace out a band, approximately 70 miles wide across fourteen states, being first visible shortly after 10:15am PDT at Oregon's Pacific coast, and finally finishing in Charleston, South Carolina. The longest duration of totality will be 2 minutes and 42 seconds, which will occur in Giant City State Park, near Carbondale, Illinois. A partial eclipse will be visible across a much broader band including all of North America, northern South America, Western Europe, and even parts of Africa. To see an interactive map of the path of the eclipse, please visit NASA's interactive Google map, or Xavier Jubier's interactive Google map. For general information about eclipse photography, please visit Fred Espenak's Eclipse web site.
On July 28, 2017, we started an MHD computation of the solar corona, in preparation for our prediction of what the solar corona will look like during this eclipse. We used data measured by the HMI magnetograph aboard NASA's SDO spacecraft. We used a combination of HMI synoptic maps, including data for Carrington rotation 2192 combined with data from a part of Carrington rotation 2193 measured up to 12:00 UTC on July 26, 2017.
This preliminary prediction of the state of the solar corona during the eclipse was posted on July 31, 2017. We intend to update this prediction on or around August 15, 2017 with newer magnetic field data.
Our prediction is based on a magnetohydrodynamic model of the solar corona with improved energy transport. While our earlier predictions incorporated a more simplistic heating formalism, for the first time, here, we have applied a wave-turbulence-driven (WTD) methodology to heat the corona. This model better reproduces the underlying physical processes in the corona, and has the potential to produce a more accurate eclipse prediction. Additionally, these simulations are among the largest we have performed, using 65 million grid points. For technical details about our model, please see the publications below.From our prediction we can estimate emission in extreme ultraviolet (EUV) wavelengths and X-rays. The EUV emission can be compared with solar observations from the EIT imager on SOHO, and the AIA instrument on SDO. X-ray emission can be compared with solar observations from the XRT instrument on Hinode. We also predict the scattering of polarized white light (polarized brightness, pB) that is typically measured during an eclipse. Movies of our simulated polarized brightness can be found below.
You can read the technical details about the calculations that were used to make our predictions.
The images above show our preliminary prediction of the polarized brightness (pB) and the magnetic field lines in the solar corona for the eclipse expected on August 21, 2017 at 17:18 UTC (corresponding to the time of peak eclipse near Salem, Oregon, which occurs at 10:18 local time). The state of the solar corona was computed using a 3D magnetohydrodynamic (MHD) simulation. The pB signal is produced by white light scattered off electrons in the coronal plasma. The image has been radially detrended using the Newkirk vignetting function to account for the fall-off of coronal brightness with distance from the Sun. Vertical (top) is terrestrial (geocentric) north. This is the view of the Sun that would be seen by an observer on Earth with a camera aligned so that vertical is toward the Earth's north pole. In the image with magnetic field lines, the Sun's surface shows color contours of the radial component of the measured photospheric magnetic field from the HMI magnetograph, showing the location of active regions (strong magnetic fields).
Our 3D wave-turbulence-driven MHD model allows us to simulate the emission from the corona in extreme ultraviolet and X-ray wavelengths. The Sun can be observed in these wavelengths from space. In particular, the SOHO/EIT, STEREO/EUVI, and AIA/SDO telescopes routinely take EUV images of the solar corona, and the Hinode/XRT telescope images the soft X-ray Sun. Our simulated coronal emission is available here.
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Z. Mikić, J. A. Linker, D. D. Schnack, R. Lionello, and A. Tarditi, "Magnetohydrodynamic Modeling of the Global Solar Corona," Physics of Plasmas, 6, 2217 (1999). Download PDF
Z. Mikić, J. A. Linker, P. Riley, and R. Lionello, "Predicting the Structure of the Solar Corona During the 11 August 1999 Total Solar Eclipse," in The Last Total Solar Eclipse of the Millennium, Proceedings of the Conference held in Istanbul, Turkey, 13-15 August, 1999 (W. Livingston and A. Ozguc, eds.), ASP Conference Series, Vol. 205, p. 162 (2000). Download PDF
Z. Mikić, J. A. Linker, R. Lionello, P. Riley, and V. Titov, "Predicting the Structure of the Solar Corona for the Total Solar Eclipse of August 1, 2006," in Solar and Stellar Physics Through Eclipses (O. Demircan, S. O. Selam, and B. Albayrak, eds.), ASP Conference Series, Vol. 370, p. 299 (2007). Download PDF
R. Lionello, J. A. Linker, and Z. Mikić, "Multispectral Emission of the Sun During the First Whole Sun Month: Magnetohydrodynamic Simulations," Astrophys. J., , 690, 902 (2009). Download PDF
V. Rušin, M. Druckmüller, P. Aniol, M. Minarovjech, M. Saniga, Z. Mikić, J. A. Linker, R. Lionello, P. Riley, and V. S. Titov, "Comparing Eclipse Observations of the 2008 August 1 Solar Corona with an MHD Model Prediction," Astron. Astrophys., 513, A45 (2010). Download PDF
P. Riley, Linker, J. A., Lionello, R., \& Mikic, Z., "Corotating interaction regions during the recent solar minimum: The power and limitations of global MHD modeling. Journal of Atmospheric and Solar-Terrestrial Physics," 83, 1-10 (2012). Download PDF
R. Lionello, M. Velli, M., C. Downs, J. A. Linker, Z. Mikić, and A. Verdini, "Validating a Time-Dependent Turbulence-Driven Model of the Solar Wind," Astrophys. J., 784, 120 (2014). Download PDF
C. Downs, R. Lionello, Z. Mikić, J. A. Linker, and M. Velli, "Closed-Field Coronal Heating Driven by Wave Turbulence," Astrophys. J., 832, 180 (2016). Download PDF
NASA's 2017 Eclipse Web Site
NASA's Eclipse Web Site
NASA's Technical Eclipse Web Site
Shadow and Substance
Xavier Jubier's 2017 Total Eclipse Interactive Google Map
Our work is supported by NASA (Heliophysics Supporting Research and Living with a Star programs), AFOSR, and NSF. We are grateful to NASA's Advanced Supercomputing Division (NAS) for an allocation on the Pleiades supercomputer, and the Extreme Science and Engineering Discovery Environment (XSEDE) for allocations on Stampede2 at the Texas Advanced Computing Center (TACC) and Comet at the San Diego Supercomputer Center, (SDSC) which allowed us to complete the eclipse prediction simulations shown here. We also thank the SDO/HMI team of the Solar Physics Group at Stanford University for their support in providing timely access to HMI Synoptic magnetograph data.