Scientists accurately predicted corona's appearance during solar eclipse

Research will help scientists predict potentially harmful space weather.
By Laurel Kornfeld | Aug 28, 2018
Scientists at the San Diego-based private research company Predictive Science, Inc., used data from NASA's Solar Dynamics Observatory (SDO) to create a simulation that accurately predicted the appearance of the Sun's corona during the August 17, 2017, total solar eclipse.

The solar corona is the outermost part of the Sun's atmosphere. Although an instrument known as a coronagraph can be used to artificially block the Sun, enabling scientists to view the corona, its lower region, located just above the Sun's surface is visible only during the brief total phase of a solar eclipse, when the Moon completely blocks out the Sun.

A dynamic region, the corona is characterized by complex magnetic fields and is the source of energy emitted during solar flares and coronal mass ejections.

If they travel in Earth's direction, these flares and coronal mass ejections, known as space weather, can disrupt satellites in orbit, knock out power grids, and disable communications systems between Earth and space.

Predictive Science, Inc.s research works toward accurately predicting these events and mitigating their worst effects.

During a total solar eclipse, company researchers can compare their computer models of the corona to its actual appearance, yielding data useful for improving the models.

The model used to predict the appearance of the corona during last year's eclipse was the most complex one the company had created in 20 years. Every individual simulation required thousands of processors and numerous computing hours. Several supercomputers were used to run the models, including the Pleiades supercomputer at NASA's Advanced Supercomputing facility in its Ames Research Center.

Among the SDO data inputted were observations of prominences or snakelike structures of erupting from the Sun's surface.

When the scientists compared their model to actual observations from the eclipse, they found a clear resemblance. Both the model and actual images showed three large, petal-shaped structures over a web of magnetic loops. Data collected indicated their calculations of heating within the corona by magnetic fields are on track.

Researchers still do not fully understand why the corona is so much hotter than the regions below it. Temperatures in the corona can exceed two million degrees Fahrenheit. Yet 1,000 miles below it, they plunge to 10,000 degrees Fahrenheit.

A thin feature known as a pseudostreamer seen jetting out of the Sun's upper right during the eclipse was missed by the model due to changes in magnetic fields in its region.

"The biggest thing I take away from this is they've got a sophisticated model that looks good, but they're limited by their observations. What the model misses is a matter of the Sun changing, and that's something they can't handle without enough observations from the right places," said Alex Young of NASA's Goddard Space Flight Center, who was not part of the study.

NASA's Parker Solar Probe, which launched this month, will be able to look inside the corona.

Findings of the study have been published in the journal Nature Astronomy.

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