Scientists have revealed the science behind the plasma emission that occurs throughout the Sun’s chromosphere

These jets, or spines, appear as thin, grass-like plasma structures, constantly erupt from the surface and then fall downwards by gravity. The amount of energy and momentum that these spikes can carry is very important in solar and plasma astrophysics. The process by which the solar wind supplies plasma, heating the sun’s atmosphere to a million degrees Celsius, remains a mystery.

It is led by astronomers at the Indian Institute of Astrophysics, which is an independent agency under the Ministry of Science and Technology (DST), the government. A multidisciplinary team of researchers from India and the UK have explained the origin of “thorns” in the sun, using laboratory experiments as an analogy. They found that the physics behind emitting paint when excited into a speaker is similar to that of solar plasma emission.

In an effort to explore the basic physics of speculum dynamics, the team turned to loudspeakers. The bass tweeter responds to excitement at lower frequencies like the rumbling sound heard in a movie. When liquid is placed over the speaker and music is played, the liquid-free surface becomes unstable after a certain frequency and begins to vibrate. A great example of the ‘Faraday delight’ observed in nature is when water droplets splash onto the partially submerged back of a male crocodile during a mating show. However, liquids such as paint or shampoo will produce an uninterrupted glow when stirring the speakers because their long polymer chains provide direction.

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The article’s authors realized that the physics underlying this paint emission must be similar to that of solar plasma emission. Then they asked what would it take to produce such a plasma jet? Sahel Dey, of the Indian Institute of Astrophysics (IIA), and first author of the study explains: “The solar plasma can be imagined as interconnected by magnetic field lines, like long chains in a polymer solution. This makes the two systems different, with different properties and orientations. In space.” Mathematically too, there are similarities in handling the voltages involved, although there are also clear differences.

“Driven by the optical similarity between the solar spines and the emission layer on the speaker, we investigated the role of the magnetic field in the Sun using numerical simulations of solar plasma. In parallel, we explored the role of polymer chains using slow-motion video imaging of Faraday waves in polymer solutions.” Murthy OVSN, co-author from Azim Premji University where the laboratory experiments were carried out. They found that the emission was preserved intact against the unstable magnetic field in the Sun, and the respective polymer chains in polymer solution, and the study was published March 3, 2022 in the journal Nature Physics.

Scientists have shown that the plasma below the visible surface of the sun (the photosphere) is always in a state of convection, like water boiling in a hot pot at the bottom. This is ultimately powered by nuclear energy released into the nucleus at high density. Roughly convection provides a periodic but powerful kick of plasma into the solar chromosphere, the shallow translucent layer above the visible solar disk. The chromosphere is 500 times lighter than the plasma in the photosphere. Therefore, this powerful kick from below, in contrast to the crocodile below, shoots chromosphere plasma outward at ultrasonic speed in the form of thin clumps or spicules.

Thistle comes in all sizes and speeds. The current consensus in the solar community is that the physics behind the short spines are different from the longer, faster spines.

This study challenges this common belief to show that the sun’s convection can naturally form all kinds of rays – both short and long. “The simulation is capable of reproducing a wide range of jets as it explores a more realistic range of parameters than previous studies,” said Piyali Chatterjee, correspondent author and principal investigator of the IIA. Team members used three different supercomputers, all from India, including the JNCASR National Supercomputer Mission Facility (Bengaluru) to run parallel scientific code on a large scale.

Professor Annapurni Subramaniam, Director of the Institute of Internal Auditors (IIA), said: “This novel that brings together solar astronomers and condensed matter experimenters is able to uncover the underlying causes of incomprehensible solar anomalies. The unifying force of physics that connects disparate physical phenomena will prove to be a driving force for greater multidisciplinary collaboration.”

The team from Bengaluru, India includes: Mr. Sahel Dey, PhD student at IIA and IISc, Dr. Piyali Chatterjee from IIA and Dr. Murthy OVSN from Azim Premji University. The UK team consisted of Dr Mariana Corsus from Aberystwyth University, Dr Jiajia Liu and Chris Nelson from Queen’s University Belfast, and Professor Robertus Erdelli from the University of Sheffield, UK.