14 DAY TRIAL // A group of scientists recently conducted a series of computer simulations on the Sun, which helped them determine why the last solar minimum had such low activity levels. The star produced far less sunspots than was expected of it during that time.
Our Sun operates in 11-year cycles, which have been documented for centuries. Periods of intense solar activity, called maximums, alternate with periods in which not much is going on. These are called solar minimums, experts say.
Back in 2001, the Sun was undergoing a maximum. After that ended, it plummeted into a period of inactivity so intense, that researchers say they never saw anything like it. They even had difficulties in finding similar periods on record.
After more than two years of delays, the Sun eventually began picking up on its activity, producing solar flares and sunspots as it should have, but at much lower levels. This started happening in 2009.
During the unusually long minimum, astronomers recorded a large number of days without sunspots. They also determined that the polar magnetic field at the solar poles was very weak.
“Sunspots have been more or less continuously observed since Galileo trained his telescope on the Sun in the early 17th century,” explains astrophysics expert Dibyendu Nandi, quoted by Space.
“One has to go back almost 100 years to find a solar minimum with a larger number of spotless days,” adds the scientist, who is based at the Indian Institute of Science Education and Research in Kolkata.
Nandi was also the leader of the new study, which used computer simulations to model no less than 210 sunspot cycles. But the scientists also added a few twists to the model.
They varied the speed of meridional (north-south) plasma circulation in the Sun's interior. The super-hot matter is apparently playing a critical role in the way sunspots develop, and in their numbers.
Simulations conducted by the team were able to reproduce Cycle 23 (that peaked in 2001) when the meridional flow was fast during the first half of the cycle, but much slower during the second half.
“The results are exciting because it demonstrates how small changes in the internal dynamics of our parent star, the Sun, can profoundly affect our technology-based society,” Nandi explains.
Details of the new investigation appear in the March 3 issue of the esteemed scientific journal Nature.