Experts have been baffled by the apparent lack of activity – with many wondering if NASA simply got it wrong.

However, Solar physicist Dean Pesnell of NASA’s Goddard Space Flight Center believes he has a different explanation.

'This is solar maximum,' he says.

'But it looks different from what we expected because it is double-peaked.'

'The last two solar maxima, around 1989 and 2001, had not one but two peaks.'

Solar activity went up, dipped, then rose again, performing a mini-cycle that lasted about two years, he said.