‘The sun is slowly waking up’: Scientists say a rise in solar storms awaits us

The sun has grown increasingly active over the past 17 years, bucking a downward trend that had solar physicists wondering whether our star was heading towards a new “grand minimum” of the kind last seen in 1830.

Beginning in the 1980s, solar activity started decreasing overall, with each subsequent 11-year sunspot cycle seeing fewer sunspots, fewer flares and fewer coronal mass ejections. Solar activity reached a nadir in 2008, which was the lull at the beginning of solar cycle 24. That year had the weakest solar activity on record.

“All signs were pointing to the sun going into a prolonged phase of low activity,” said Jamies Jasinski of NASA’s Jet Propulsion Laboratory in a statement. “So it was a surprise to see that trend reversed. The Sun is slowly waking up.”

Jasinski led research that compiled data from a variety of missions studying both the sun and the solar wind, which is a stream of charged particles radiating from the sun.

The study showed that since 2008, all indicators have been increasing. Among them, solar-wind velocity is up 6%, solar wind density has increased 26%, the solar-wind temperature has seen a rise of 29% and there has been a jump in the strength of the interplanetary magnetic field carried by the solar wind equal to about 31%. This is all reflective of increased magnetic activity on the sun.

Indeed, with increased solar activity comes more geomagnetic storms that generate auroral lights in Earth‘s sky; increased coronal mass ejections and radiation flares pose greater danger to satellites, space stations and astronauts.

Why the sun has reversed course remains a large unknown — though it has happened before.

Between 1645 and 1715, there was a period that has come to be known as the Maunder Minimum, named after the late nineteenth century and early twentieth century astronomer Edward Maunder, who first noticed the 11-year solar cycle by watching how the number of sunspots waxes and wanes. Looking at historical records, Maunder realized that between 1645 and 1715, there had been no more than 50 sunspots on the sun in total. This is an extraordinarily low number, and is indicative of there being very little magnetic activity of the kind that produces flares and coronal mass ejections. For comparison, during the time of maximum activity in an ordinary solar cycle, there can be more than a hundred sunspots. Another low activity period also occurred between 1790 and 1830.

Intriguingly, the Maunder Minimum coincided with a period anecdotally referred to as the “Little Ice Age,” which saw a sequence of exceptionally cold winters across the Northern Hemisphere, prompting the River Thames in London to completely freeze over on several occasions. While there have been attempts to connect the Little Ice Age with the Maunder Minimum, the Little Ice Age began before the onset of the Maunder Minimum, and some researchers even suggest that it ran from 1300 to 1850.

The cause of the Little Ice Age is unclear, but volcanic activity belching volcanic ash high into the atmosphere and blocking sunlight is one of the most likely explanations. On the other hand, variations in solar activity such as the Maunder Minimum, the period between 1790 and 1830 and the decrease between the 1980s and 2008 do not seem to have much of an effect on Earth’s climate, and any cooling they appear to cause is being overridden by the much greater warming effects resulting from human-induced climate change.

Nevertheless, periods such as the Maunder Minimum and the years leading up to 2008 are difficult for scientists to explain. Whereas the sun’s 11-year cycle of magnetic activity is fairly well understood, “The longer-term trends are a lot less predictable and are something we don’t completely understand yet,” said Jasinski.

The findings were published on Sept. 8 in The Astrophysical Journal Letters.