Coronal Prediction for the July 2, 2019 Total Solar Eclipse

Preliminary Prediction

Brightness (Newkirk Filter)
Log Brightness (Unsharp Masked)
Click on the images to see slideshow of larger versions

This is our preliminary prediction of the solar corona for the July 2, 2019 total solar eclipse. The above images show two versions of the predicted white light brightness 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 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. For this eclipse we are showing brightness for the primary prediction, as this is closer to what an observer sees with their naked eye. In past eclipse predictions we showed polarized brightness, which may be more useful for scientific purposes. The polarized brightness can be viewed here .

The image below on the left shows a digital processing of the 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.


Brightness (Wavelet Filtered)
Magnetic Field Lines
Click on the images to see slideshow of larger versions

These images are aligned so that terrestrial (geocentric) north is up, for the time of totality (20:41 UT) near San Juan, Argentina. 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.


Volume-rendered Magnetic Squashing Factor Q
(Eclipse Day View)
Volume-rendered Magnetic Squashing Factor Q
(Movie with Rotating Q)
Click on the image to see larger version | Click here to download movie

The last set of images show a special visualization of the three-dimensional (3D) magnetic field. By tracing magnetic field lines at extremely high resolution, we can calculate a 3D map of the so-called squashing factor - a scientific measure designed to indicate the presence of complex structuring in the magnetic field. We then integrate the map along the line-of-sight, with special weightings to create a composite that resembles solar eclipse images. This is intended to highlight the inherent complexity of the Sun's magnetic field and its intimate connection to visible emission from the solar corona.


Modeling the Corona for the Total Solar Eclipse

On July 2nd, 2019, a total eclipse of the Sun will be visible across the South Pacific, Chile, and Argentina. Although the longest duration of totality will be 4 minutes and 33 seconds, this will occur in the middle of the Pacific. Technically, landfall will occur over the uninhabited island of Oeno (a British Territory) in the middle of the South Pacific Ocean; However, Chile and Argentina are the best places on land to see totality. But even there, the eclipse will only be 12 degrees high and durations will be limited to about 2 minutes or less. It will finally move out into the Atlantic Ocean just before Sunset. To see an interactive map of the path of the eclipse, please visit Xavier Jubier's interactive Google map. For more information, as well as an interactive Google map showing the path of the eclipse, visit Fred Espenak's Eclipse website.

On May 31, 2019, 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 2216 combined with data from a part of Carrington rotation 2217 measured up to 12:00 UTC on May 29, 2019. You can read the details about the evolution of the photospheric magnetic field that was used to make our prediction.

Our prediction is based on a magnetohydrodynamic model of the solar corona with improved energy transport. We have applied a wave-turbulence-driven (WTD) methodology to heat the corona, that we first used in our prediction for the August 21, 2017 eclipse. This model better reproduces the underlying physical processes in the corona than previous empirical models, and has the potential to produce more accurate estimates of physical quantities. This simulation employs some updates to our technical approach and heating parametrization to better match the current solar conditions. This simulation is also among the largest we have performed, using 66 million grid points. For technical details about our model, please see publications.

As we did for the August 21, 2017 eclipse , we introduced magnetic shear along polarity inversion lines (PILs - lines separating positive and negative polarity regions) where filament channels were observed in EUV emission by SDO/AIA. This is a well-known feature of large-scale coronal magnetic fields. The handedness of the shear was estimated using the hemispheric rule in quiet sun, and by visual inspection of AIA images for active regions (see Energization). The introduction of shear qualitatively changes the shape of the streamers and the connectivity of the underlying fields, and increases the free magnetic energy in the corona.

From our model, we can predict quantities that can be observed directly. We provide images of the total brightness (B) and the polarized brightness (pB). The B resembles what is seen by the naked eye. However, pB is the more scientifically useful quantity. Traditionally, pB has been used to separate light scattered by the K-corona and the F-corona. The K-corona is the photospheric light scattered by electrons in the corona, while the F-corona is the photospheric light scattered by dust, which is unpolarized. Note that we do not model the F-corona so its contribution to B is not included.

We can also estimate emission in extreme ultraviolet (EUV) wavelengths and X-rays. The EUV emission can be compared with solar observations from the AIA instrument on SDO. X-ray emission can be compared with solar observations from the XRT instrument on Hinode.

You can read the technical details about the calculations that were used to make our predictions.


Additional Materials

Brightness
Polarized Brightness
Coronal Emission
Magnetic Field Lines

Publications

For technical details about our model, please see the following publications:


Other Resources for the Solar Eclipse


Acknowledgments

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 and Electra supercomputers, 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.



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