
Solar physicists may have discovered why the Sun recently experienced a prolonged period of weak activity.
The most recent so-called "solar minimum" occurred in December 2008.
Its drawn-out nature extended the total length of the last solar cycle - the repeating cycle of the Sun's activity - to 12.6 years, making it the longest in almost 200 years.
During a solar minimum the Sun is less active, producing fewer sunspots and flares.
The new research suggests that the longer-than-expected period of weak activity may have been linked to changes in the way a hot soup of charged particles called plasma circulated in the Sun.
The study, conducted by Dr Mausumi Dikpati of the National Center for Atmospheric Research in Colorado and her US colleagues, is published in the journal Geophysical Research Letters.