One year ago on August 21, 2017, millions of Americans were treated to a stunning total solar eclipse across the country. But a group of scientists were awaiting a monumental moment of their own.
During a total solar eclipse, the Sun’s corona – its outer atmosphere – becomes visible around the Moon in a rare event. Normally, the corona is particularly hard to study owing to the brightness of the Sun.
So in the build up to the American eclipse, a team from Predictive Science Inc. based in San Diego published a study predicting what the solar corona would look like. They developed a model that simulated what the corona should look like, and eagerly awaited their results.
“Waiting for totality, you know exactly what you’ve predicted and what you’re expecting,” Predictive Science researcher Zoran Miki? said in a statement. “Because you work with the model so much and see the prediction so many times, it’s burned into your brain. There’s a lot of anxiety because if you’re totally wrong, it’s a bit embarrassing.”
But it was mostly good news for the scientists. Publishing their findings in Nature Astronomy, the team said their prediction was very similar to the actual corona they observed. They were able to predict how the Sun’s twisting magnetic fields would affect the visible corona.
To make the model work, they fed computers and supercomputers data on the Sun’s magnetic field for the preceding 27 days before the eclipse, which is the time it takes the Sun to make an entire rotation. This let them get a better handle on how solar prominences, large and bright streams of gas, would appear. They also used images from NASA’s Solar Dynamics Observatory (SDO).
“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,” the team wrote in their paper.
However, their model did lack some of the finer structures seen in the corona, such as a jet streaming out from the Sun’s upper-right called a pseudostreamer. This was likely due to a magnetic field changing in that region in a way that wasn’t predicted.
While the science itself is interesting, it is also important. Results like this could help us more accurately predict space weather, as the Sun throws particles and solar wind in our direction. This can affect satellites and even planes flying through the air, so getting better at predicting it is incredibly useful.