Even ‘asleep’ for 70 years, Sun’s ‘clock’ kept ticking: study

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In 1645, the Sun – then a 4.5 billion year old star – went dormant and almost stopped producing sunspots. As the Sun continued to remain in this dark phase for the next 70 years, known as the Grand Solar Minimum, overall solar activity remained below normal.

In a bid to dig deeper and understand the behavior of the Sun over these seven decades, a group of scientists from the Indian Institute of Science Education and Research (IISER) in Kolkata conducted one of the longest computer simulations of historical solar activity spanning 10,000 years.

The group has now found that even during the Sun’s period of extreme inactivity between 1645 and 1715, also known as the Maunder Minimum, the giant star and its dynamo mechanism never stopped working.

The Sun is constantly burning hydrogen to produce helium, this is called nuclear fusion. As a giant ball of hot gas located at the center of our solar system, it is the sun’s energy that sustains life on Earth; its gravity that keeps planets and stars intact. Any change to the solar surface or its periphery, however small, can affect the Earth’s atmosphere and space weather. Powerful solar storms and solar flares are potentially harmful to satellite-based earth operations, the operation of power grids and navigation networks. Although there is limited historical observational data on the past Sun, researchers at the Center of Excellence in Space Science, India (CESSI), IISER, Kolkata, used computer models to understand how this star formed. behaves over 10,000 years. time limit.

The constant churning of electrically charged particles known as plasma inside the Sun produces the Sun’s magnetic field through a process known as the solar dynamo mechanism. This in turn produces the 11-year solar cycle. Once every 11 years, the north and south magnetic poles of the Sun reverse their polarity. During each of these cycles, solar activity increases and decreases, along with the appearance of sunspots (regions of super strong magnetic fields on the Sun appearing as dark spots)

“During years of large minima, magnetic field production in the convective zone of the Sun weakens due to turbulent fluctuations reducing the ability of the Sun to produce sunspots,” said Professor Dibyendu Nandi, director of CESSI, at The Indian Express.

“But the absence or fewer sunspots does not mean that the 11-year solar cycle has completely died out,” said co-author Sanghita Chandra, a former undergraduate student at IISER Kolkata and currently pursuing her studies. PhD studies at the Max Planck Institute for Solar System Research. , Germany.

Instead, their research revealed that the Sun’s internal solar cycle “clock” kept ticking. Their findings, published in the Monthly Notices of the Royal Astronomical Society Letters, link this clock to the meridian circulation – a large-scale river-like plasma flow inside the Sun.

“Based on our computer simulations, we believe that the meridian circulation continues during grand minima of solar activity, contrary to some previous opinions. This circulation acts as a timekeeper and always maintains a weak cycle inside the Sun. during quiet (minima) phases,” said Chitradeep Saha, lead author and third-year doctoral student at IISER, Kolkata. Studying such puzzling events in the Sun required clever computer modeling and complex data analysis. spanning thousands of years of simulated solar activity data.

“Computer experiments showed that when the meridian circulation velocity was slowed, the period of weak solar cycles increased and vice versa. Computer models have become an important tool around the world, helping us create the Sun in a computer and study it,” Nandi said.

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