Europe is witnessing its first total solar eclipse in 27 years on Wednesday.
A solar eclipse occurs when the Moon passes between the Sun and the Earth, blocking out some or all of the star’s light. The latter phenomenon happens during a total solar eclipse. It is a rare occurrence, requiring the Sun, the Moon and the Earth to line-up perfectly in space.
While not all of Europe will experience “totality” — the phase when the Moon completely covers the Sun’s surface — large parts of the continent will still experience near night-like conditions.
A solar eclipse also happens to be the best time for scientists to study the Sun. Here’s what they study at that time — and how they do it.
First, where is the total eclipse visible today?
The August 12 total solar eclipse is not visible from any location in India.
The total eclipse can be seen along the north of Russia, Greenland, west Iceland, northern Spain and a small area along northeast Portugal.
Together, these locations form the “path of totality” — the narrow strip on the Earth’s surface where the Moon can be seen completely blocking the Sun.
The “path of totality” of the August 12 solar eclipse. (NASA)
Large parts of the continent will witness a partial solar eclipse — most UK residents, for instance, will be able to see more than 90% of the Sun being covered by the Moon.
Outside of Europe, the partial eclipse would be visible over North America and northwest Africa.
The total solar eclipse is expected to last for two minutes and 18 seconds, occurring over Látrabjarg, Iceland.
In any total solar eclipse, the duration of “totality” is the longest near the centre of the path of totality widthwise and diminishes towards the edges.
Why do scientists need to study the Sun?
For scientists, observing the Sun’s corona and the inner corona is crucial. The corona’s magnetic field triggers solar flares and “coronal mass ejections”, which can disrupt satellites, GPS and other communication systems on Earth.
The corona is the Sun’s outermost atmosphere, extending millions of kilometres into space. The inner corona is the part of the Sun’s outer atmosphere that is closest to the star’s surface.
However, it is extremely faint. To study it, scientists need to block the solar disc artificially using an instrument called a coronagraph, which is usually placed on solar probes or missions. On many occasions, however, these instruments are affected by scattered light — making it impossible to observe the inner corona.
This is where an eclipse comes in.
How does a solar eclipse help in this study?
During a total solar eclipse, the Moon completely blocks the solar disc, making the inner corona visible in the form of a halo around the lunar body.
This provides helio-physicists with a valuable window to make ground-based observations of the solar atmosphere.
“When an eclipse happens, the bright inner disk gets blocked and the fainter outer atmosphere gets revealed, which is the solar corona. The eclipse thus gives us clues to the underlying magnetic structure of the Sun’s corona,” Dibyendu Nandi, an astrophysicist from the Raman Research Institute, told The Indian Express.
Another factor to consider is the solar cycle — the roughly 11-year cycle during which the Sun’s activity rises and falls, marked by changes in the number of sunspots, solar flares and other activity.
In the current solar cycle, which began in 2020, the Sun has already passed its maxima phase — the period when it is most active and when more structures in the inner corona are likely to be visible.
Owing to these reasons, scientists plan multiple experiments and solar observations during total solar eclipses, particularly from the location where the maximum eclipse is expected.
What can scientists observe during the total solar eclipse ?
During the eclipse, an Indian group of researchers at Centre of Excellence for Space Science India (CESSI), IISER-Kolkata, has predicted the possibility of spotting multiple large-scale streamers, which are petal-like structures.
“These are nothing but bright magnetic field structures rooted to the solar surface. There is no other way to see the magnetic fields, because the Sun’s disc is bright. During a natural eclipse, it is possible to see the Sun’s corona from the ground, too,” Nandi said.
If these magnetic field structures are spotted during the event, scientists expect them to be highly complex and spectacular.
A total solar eclipse is seen from Arlington, Texas(AP Photo) 
The “path of totality” of the August 12 solar eclipse. (NASA)
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