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CESSI team accurately predicts shape of Sun’s corona 43 days ahead of eclipse

Image shows the LASCO C2 instrument's observation (outer image) overlaid on the predicted large scale coronal magnetic field lines (inner image).

Image shows the LASCO C2 instrument's observation (outer image) overlaid on the predicted large scale coronal magnetic field lines (inner image).   | Photo Credit: SOHO-CESSI

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This gives a large window of preparedness for space weather driven by coronal magnetic fields, says principal investigator

Solar physicists from the Centre for Excellence in Space Sciences (CESSI), IISER Kolkata, have succeeded in predicting the shape of the sun’s atmosphere — known as the corona — at the time of the annular eclipse of December 25.

This is the second successful prediction, counting the last solar eclipse that was viewed from South America on July 2 this year. While the earlier prediction was slightly different from the actual image, this time it is pretty close to the real thing, which was imaged by NASA’s spaced-based solar observatory SOHO using the LASCO instrument.

“For the South American eclipse of 2 July, 2019, our predicted streamer tilts were slightly larger than observed at large distances from the Sun. This is far better. We are still trying to figure out why this worked so well this time,” says Dibyendu Nandi, professor and principal investigator at CESSI.

The Predictive Solar Surface Flux Transport model developed by the CESSI Team can predict the shape of the corona well ahead ahead of any required date. Prantika Bhowmik, now at Durham University, U.K., developed this model with Dr. Nandi. This is now being further improved by Soumyaranjan Dash, a PhD student at IISER Kolkata.

“Our previous research exploring this prediction method indicates that we can predict the large-scale structure of the Sun’s corona up to two months in advance. This is great because this gives you advance knowledge and a large window of preparedness for space weather driven by coronal magnetic fields,” says Dr. Nandi.

Space weather consists of the varying conditions within the solar system such as solar wind and is different from weather on earth. It can affect the electronics on board satellites.

This time, they had used inputs and made the prediction 43 days ahead of the eclipse. “The only way to verify these models is to either have photographs taken during the eclipse that capture the corona or use space- or ground-based instruments that use an artificial disc to occult the Sun’s surface to make the faint corona visible,” explains Dr. Nandi in an email to The Hindu.

This time, since this was an annular eclipse with a ring of bright solar surface visible, the corona was not directly noticeable. The only option was to use a coronagraph with an occulting disc. “The only functional one in the world is in Hawaii in Mount Muana Lea, which has been having bad weather. Also, it was night in Hawaii when the eclipse happened,” Dr. Nandi adds.

The researchers used the images generated by the space-based coronagraph instrument LASCO on board the European Space Agency’s SOHO satellite.

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Printable version | Jan 24, 2020 6:58:22 AM | https://www.thehindu.com/sci-tech/science/cessi-team-accurately-predicts-shape-of-suns-corona-43-days-ahead-of-eclipse/article30409270.ece

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