Research on Corona Sun | Why Corona is too hot to handle: Indian researchers point to the sun’s magnetic dance

Nearly two years ago, a region of the sun erupted, spewing giant blobs of hot plasma into space, and the imprint of the event was captured by Aditya-L1, an Indian space observatory located about 1.5 million kilometers from Earth.

Now, scientists have used these observations to extract new evidence that the constant dance of magnetic fields in the sun’s atmosphere may hold the key to explaining one of the sun’s oldest mysteries: its extremely hot outer atmosphere.

The study, conducted by a team of researchers at the Indian Institute of Astrophysics (IIA) in Bengaluru, addresses a long-standing solar mystery: why the temperature of the Sun’s corona, or outer atmosphere, is typically around 1 million degrees Celsius and can reach tens of millions of degrees during powerful outbursts, while the Sun’s visible surface is only about 6,000 degrees.

Over the past several decades, scientists have proposed two mechanisms that could heat the corona, including waves that carry energy and deposit heat in the corona, and the explosive release of energy when magnetic fields are interrupted, reconnecting and rearranging themselves.

Now, R. Ramesh and his colleagues at the IIA found that waves—ripples that travel through the Sun’s magnetic environment—account for only 7 percent of the energy in the regions where explosions occur in the solar atmosphere.

Their findings, published in Astrophysical JournalIt suggests that reshaping of the Sun’s magnetic fields accounts for the bulk of energy transfer, adding new evidence to explain both excessive coronal heating as well as rapid replenishment of lost energy.

“For decades, physicists have used mathematics and computers to model how the Sun’s magnetic fields store and release energy,” Ramesh said. Telegraph. “What was missing was direct observational evidence of how energy actually transfers during such explosions.”

IIA scientists analyzed the signatures of a coronal mass ejection (CME), the sudden ejection of plasma blobs from the Sun’s surface. CMEs may occur once or twice per day during the Sun’s “quiet” phase, but an additional 10 CMEs per day may occur during periods of peak solar activity.

The crucial observations came from an instrument aboard Aditya-L1, which can capture images and analyze light from the coronal in detail, allowing researchers to infer changes in plasma motion and physical conditions during a coronal ejection.

The Indian space agency will launch Aditya-L1, a dedicated space solar observatory, in 2023.

“This work demonstrates the unique capability of continuous observation using the Aditya-L1 instrument,” Dibyendu Nandy, a solar physicist at the Raman Research Institute in Bengaluru, who was not involved in the IIA study, told this newspaper. But the results so far come from a single CME observation in August 2024, he said.

“Determining statistically whether the findings apply to a large number of events will be an important future step,” Nandy said. The IIA team now plans to conduct similar analyses
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The hot corona mystery has its roots in a green spectral line discovered by two American astronomers while observing a total solar eclipse in 1869. Scientists initially believed that
The line came from a previously unknown item they called the “crown”.

But seventy years later, a Swedish physicist discovered that the streak came from super-hot iron, stripped of nearly half of its electrons, implying that the temperature of the corona was more than a million degrees, roughly 150 times hotter than the surface of the Sun.