(24.11.2013) The polar reversal takes place as the Sun’s magnetic field moves north or south from the equator, eroding the existing pole as it does, explains Todd Hoeksema, a scientist at Stanford University’s Wilcox Solar Observatory.

Phil Scherrer, who works with Mr Hoeksema, said: “The north pole has already changed sign, while the south pole is racing to catch up.

It looks like a complete field reversal could be “no more than three to four months away,” said Mr Hoeksema in early August.