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City moon figures out Sun
- Physicist solves spot mystery that baffled astronomers

New Delhi, March 2: A moon on Earth has shed light on the Sun.

A Calcutta physicist whose first name translates as “bright moon” has used computer simulations of the hot plasma sloshing in the interior of the Sun to explain an unusually long-lasting absence of sunspots two years ago that had baffled astronomers worldwide.

The research, led by Dibyendu Nandi at the Indian Institute of Science Education and Research, Calcutta, explains why the Sun lost its sunspots for nearly two years in 2008 and 2009 and may emerge a tool for forecasts of space weather.

Sunspots, first described by Italian astronomer Galileo Galilei in the early 17th century, are strongly magnetised regions visible as dark spots on the solar surface. The number of sunspots changes over time, touching highs and lows, in cycles of about 11 years. But the last sunspot cycle that peaked around 2000-01 ended with a prolonged and puzzling period of days without sunspots in 2008 and 2009.

“This was completely unexpected — many of us were wondering what was happening inside the Sun,” said Nandi, who collaborated with two scientists in the US to simulate the flow of plasma within the solar interior that generates solar cycles.

In their simulations, Nandi and his co-workers, Andres Munoz Jaramillo and Petrus Martens, at the Harvard Smithsonian Center for Astrophysics were able to reproduce the observed large number of days without sunspots as well as the weak magnetic field strengths.

Their study suggests that a fast flow of the plasma — whose movement resembles that of a conveyor belt — during the first half of a solar cycle followed by a slower flow in the second half results in a prolonged period without sunspots. The research will appear tomorrow in the journal, Nature.

“This is the first model to provide a rationale and reproduce the main features of this extended solar minimum,” said Madhulika Guhathakurta, an astrophysicist with the Nasa headquarters in Washington DC who was not associated with this study. “For something as complicated as the solar cycle, this model has produced remarkable results,” Guhathakurta told The Telegraph.

Sunspots influence the energy output of the Sun — the greater the number of sunspots, the higher is the energy output. This, in turn, increases the heat received by the Earth, which determines the planet’s weather and climate.

Researchers believe the simulations may also represent a major step towards predicting space weather triggered by magnetic storms from sunspots that carry plasma deep into space and may disrupt sensitive equipment on spacecraft or aircraft flying polar routes.

“Space weather is important for planning space missions, estimating satellite lifetimes and scheduling air traffic on polar routes. Just as we like warnings about bad weather, we would like to predict periods of good space weather,” Nandi said. “So much human activity now depends on satellites — ATM machines, navigation, television services — and our dependence on space weather is going to increase exponentially in the coming years,” he said.

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