"Are we ready? Understanding just how big solar flares can get"
From Knowable Magazine, September 17:
Recasting the iconic Carrington Event as just one of many superstorms in
Earth’s past, scientists reveal the potential for even more massive,
and potentially destructive, eruptions from the sun
On May 1, 2019, the star next door erupted.
In a matter of
seconds, Proxima Centauri, the nearest star to our sun, got thousands of
times brighter than usual — up to 14,000 times brighter in the
ultraviolet range of the spectrum. The radiation burst was strong enough
to split any water molecules that might exist on the temperate,
Earth-sized planet orbiting that star; repeated blasts of that magnitude
might have stripped the planet of any atmosphere.
It would be bad news if the Earth’s sun ever got so angry.
But
the sun does have its moments — most famously, in the predawn hours of
September 2, 1859. At that time, a brilliant aurora lit up the planet,
appearing as far south as Havana. Folks in Missouri could read by its
light, while miners sleeping outdoors in the Rocky Mountains woke up
and, thinking it was dawn, started making breakfast. “The whole of the
northern hemisphere was as light as though the sun had set an hour
before,” the Times of London reported a few days later.
Meanwhile,
telegraph networks went haywire. Sparks flew from equipment — some of
which caught on fire — and operators in Boston and Portland, Maine,
yanked telegraph cables from batteries but kept transmitting, powered by
the electrical energy surging through the Earth.
The events of
that Friday evoked biblical descriptions. “The hands of angels shifted
the glorious scenery of the heavens,” reported the Cincinnati Daily Commercial.
The actual impetus was a bit more prosaic: The skies had been set
ablaze by an enormous blob of electrically charged gas, shot out from
the sun following a flash of light known as a solar flare.
Space weather encapsulates the prevailing
conditions in the solar system caused by the solar wind and the sun’s
far-reaching magnetic field. Sudden changes on the sun, such as flares
and eruptions of material, are like weather fronts, bringing with them
magnetic “storms” that can be felt on the planets. On Earth, this can
cause stunning auroras, but it can also create havoc with electronics.
The flash of light from a flare takes about 8 minutes to reach Earth;
solar material expelled from the sun in a coronal mass ejection (CME)
may take hours to days to travel the distance. Magnetic storms may be
brief or last for many days.
Such a blob — a tangle of plasma and magnetic fields — is
known as a coronal mass ejection. Upon arrival at Earth, such an
ejection can trigger the most ferocious of geomagnetic storms. The 1859
storm, named the Carrington Event for the scientist who witnessed the
flare that preceded it, has long been upheld as the most powerful wallop
that the sun has ever delivered.
But in recent years, research
has indicated that the Carrington Event was just a taste of what the sun
can throw at us. Tree rings and ice cores encode echoes of dramatically
stronger solar storms in the distant past. And other stars, such as
Proxima Centauri, show that even the most energetic documented solar
outbursts pale in comparison with what is possible....
