62 Scientific American, December 2021
The first indication that solar storms could be even worse
came in 2012, with the discovery of a mega storm some 10 to
100 times stronger than the Carrington Event that occurred
around a.d. 775. “It was really, really astounding,” says Nico-
las Brehm of ETH Zurich. “We didn’t think something of this
magnitude could happen.”
The ancient mega storm might have come from a once-
in-10,000-years “superflare,” an event thousands of times
more powerful than a regular solar flare, scientists specu-
lated at the time. A direct hit by such a superflare today
would have devastating consequences for our globally
wired society.
Now these phenomena appear to be even more common
than we thought: researchers investigating the geochemi-
cal annals of Earth’s recent history have now found evi-
dence for two more.
In a paper led by Brehm, available as a preprint on Re -
search Square, scientists reveal the possible discovery of two
frightfully strong solar events. One occurred in 7176 b.c.,
when nomadic hunter-gatherer societies were giving way to
agrarian settlements. The other happened in 5259 b.c., as
the planet emerged from the last ice age. Both events are
thought to have been at least as strong as the one in a.d. 775,
and for the past decade scientists have been searching for
similarly extreme occurrences. Brehm’s team is the first to
find some. “It’s a great achievement,” says Fusa Miyake of
Nagoya University in Japan, who led the study in 2012 that
revealed the 775 event. Scientists now refer to such super-
flares as “Miyake events.”
To look for these solar flares, researchers rely on chemical
analyses of samples from polar ice caps and from ancient
trees preserved in waterlogged bogs or high on mountain-
tops. When solar particles hit the atmosphere, they can pro-
duce unstable radioactive forms of various elements, called
isotopes, that accumulate in these places. For example, solar
activity can form carbon 14, which is absorbed by trees as they
E
very now and then our star produces
immense flares of particles and ra di-
a tion that can wreak havoc on Earth.
For more than 150 years scientists
studying these outbursts and how they
affect our planet have placed great
focus on a single, seemingly pinnacle
example: the Carrington Event of 1859. An eruption from
the sun walloped Earth, pumping enough energy into our
planet’s magnetic field to set off a massive geomagnetic
storm that created beautiful auroral displays but also
sparked electrical fires in telegraph lines. The storm was
seen as an odd, minor inconvenience that caused limited
damage to the electrical infrastructure of the time.
Researchers today, however, recognize the Carrington
Event, along with a 1921 storm of comparable strength, as
an ominous warning of future catastrophes.
Jonathan
O’Callaghan
is a freelance
journalist covering
commercial
spaceflight, space
exploration
and astrophysics. NASA, SDO and the AIA, EVE and HMI science teams
(^ all photographs
)
