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The wild and turbulent activity of a sunspot can now be seen in fascinating detail, thanks to a newly released image from a new solar observatory.
In Hawaii, the Daniel K. Inouye Solar Telescope (DKIST) is still in the final stages of completion, but its first image of a sunspot, taken on January 28, 2020 (not the sunspots that appeared in late November ), it is already the most detailed we have seen.
“The sunspot image achieves a spatial resolution roughly 2.5 times higher than ever, showing magnetic structures as small as 20 kilometers (12 miles) on the sun’s surface,” said astronomer Thomas Rimmerle of the National Solar Observatory of the NSF.
Sunspots are of great interest to us here on Earth. Most of the Sun’s surface looks like the popcorn area around the sunspot. Each of these granules is a convection cell; hot plasma rises in the middle, moves toward the edges as it cools, and descends back toward the Sun. And they are huge: a typical granule is about 1,500 kilometers (930 miles) wide.
(NSO / AURA / NSF)
Sunspots are temporary patches where the Sun’s magnetic field becomes particularly strong, inhibiting the star’s normal convection activity. Because the magnetic field lines prevent the hot plasma from rising from the inside, the sunspot is about one-third cooler than the area around it and appears darker.
Those magnetic field lines are responsible for another phenomenon that affects us here on Earth. As they become entangled, broken, and reconnected, they can release enormous amounts of energy, triggering solar flares and coronal mass ejections.
These flares from the Sun are so powerful that they can disrupt satellite communications, navigation and, in severe cases (fortunately very rare), render power grids without power.
So scientists are very interested in learning more about sunspots and how they work, and DKIST, in this image taken during its commissioning phase (basically testing that everything works properly), has shown how powerful it will be in that context.
(NSO / AURA / NSF)
The image is about 16,000 kilometers (10,000 miles) wide and the Earth, with a diameter of 12,742 kilometers, could fit comfortably within the sunspot, the researchers said. As they imaged the region, they were able to track changes in the fine structure on short timescales, around 100 seconds. This can be seen in the gif above.
“For example, narrow dark lanes are consistently seen at both threshold points (UD) and penumbral grains (PG). Some typical examples are marked with arrows,” the researchers wrote.
“The dark, narrow lanes within bright UDs and PGs have been predicted by numerical magnetoconvection simulations and are a consequence of strong upward flux columns in areas of lower magnetic field intensity. The dark lanes evolve significantly over 100 seconds giving the impression of small-scale inverted convection that occurs in these features. DKIST’s spectropolarimeters will allow detailed analysis of these features on a small-scale and comparison with model predictions. “
In the months and years to come, DKIST will likely prove invaluable. We are entering a period of increased solar activity known as solar maximum. These oscillate every 11 years and are characterized by a marked increase in sunspots and flares.
A better understanding of the physics behind solar activity is a tool that scientists hope will refine our ability to predict solar weather. And that starts with observations.
“With this solar cycle just beginning, we are also entering the era of the Inouye Solar Telescope,” said astrophysicist Matt Mountain of the Association of Universities for Research in Astronomy, which runs DKIST.
“We can now point to the Sun with the world’s most advanced solar telescope to capture and share incredibly detailed images and add to our scientific insights into the Sun’s activity.”
The team article has been published in Solar physics.
