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the existence of a Space Weather Service, a network of observato-
ries, satellites, data banks, and experts that monitored the sun and
its stormy environs, and tried to predict the worst of its transgres-
sions. There was even a weather station at the South Pole of the
Moon, it seemed.
Despite decades of watching the moody sun, though, only one
person had predicted today s unusual events, a young scientist on
the Moon called Eugene Mangles, who had logged quite precise
forecasts on a few peer-review sites. But the Moon was out of touch.
3 6 " C L A R K E & B A X T E R
Thirty minutes after last speaking with her, Siobhan called
Phillippa Duflot again.
It s all to do with the sun, she began.
Phillippa said, We know that much
It has given off what the sungazers call a coronal mass ejec-
tion.
She described how the corona, the sun s extended outer at-
mosphere, is held together by powerful magnetic fields rooted in
the sun itself. Sometimes these fields get tangled up, often over
active regions. Such tangles will trap bubbles of superheated plasma,
emitted by the sun, and then violently release them. That was what
had happened this morning, over the big sunspot continent the ex-
perts were calling Active Region 12688: a mass of billions of tonnes
of plasma, knotted up by its own magnetic field, had been hurled
from the sun at a respectable fraction of the speed of light.
The ejection took less than an hour to get here, Siobhan said.
I understand that s fast, for such phenomena. Nobody saw it com-
ing, and nobody was particularly expecting it to happen at this stage
of the sun s cycle anyhow. Except, she made a mental note, that
lone astronomer on the Moon.
Phillippa prompted, So this mass of gas headed for the
Earth
The gas itself is sparser than an industrial vacuum, Siobhan
said. It s the energy contained in its particles and fields that has
done the damage.
When it hit, the mass ejection had battered at the Earth s mag-
netic field. The field normally shields the planet, and even low-
orbiting satellites, but today the mass ejection had pushed the field
down beneath the orbits of many satellites. Exposed to waves of en-
ergetic solar particles, the satellites systems absorbed doses of static
electricity that discharged wherever they could.
Imagine miniature lightning bolts sparking around your cir-
cuit boards
Not good, Phillippa said.
No. Charged particles also leaked into the upper atmosphere,
dumping their energy on the way that was the cause of the auro-
rae. And Earth s magnetic field suffered huge variations. Perhaps
S U N S T O R M " 3 7
you know that electricity and magnetism are linked. A changing
magnetic field induces currents in conductors.
Phillippa said hesitantly, Is that how a dynamo works?
Yes! Exactly. When it fluctuates, Earth s field causes immense
currents to flow in the body of the Earth itself and in any con-
ducting materials it can find.
Such as our power distribution networks, Phillippa said.
Or our comms links. Hundreds of thousands of kilometers
of conducting cables, all suddenly awash with fast-varying, high-
voltage currents.
All right. So what do we do about it?
Do? Why, there s nothing we can do. The question seemed
absurd to Siobhan; she had to suppress an unkind impulse to laugh.
This is the sun we re talking about. A star whose energy output
in one second was more than humankind could muster in a million
years. This mass ejection had caused a geomagnetic storm that
went far off the scales established by the patient solar weather
watchers, but to the sun it was nothing but a minor spasm. Do, in-
deed: you didn t do anything about the sun, except keep out of its
way. We just have to sit it out.
Phillippa frowned. How long will it last?
Nobody knows. This is unprecedented, as far as I can make
out. But the mass ejection is fast moving and will pass over us soon.
Only hours more, perhaps?
Phillippa said earnestly, We need to know. It s not just power
we have to think about. There s sewage, the water supply . . .
The Thames barrier, Toby said. When is high tide?
I don t know, Phillippa said, making a note. Professor
McGorran, can you try to nail down a timescale?
Yes, I ll try. She closed down the link.
Of course, Toby said to Siobhan, the sensible thing to do
would be to build our systems more robustly in the first place.
Ah, but when have we humans ever been sensible?
Siobhan continued to work. But as time wore on the comms links
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