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like the monster that hit us on June 9 large-scale outpourings of
plasma flung at us from the sun s surface. And then you have flares.
These detonations on the sun s surface, powered by magnetic flaws,
are the largest explosions in the modern-day solar system, each
amounting to the blast of billions of nuclear weapons. Flares bom-
bard us with radiation from gammas to radio waves. Sometimes
they are followed up by what we call solar proton events cascades
of charged particles.
The restless sun follows an eleven-year solar cycle, at the
peak of which sunspots swarm and flares erupt with much more
vigor than at its minimum. Mikhail sketched the accepted mecha-
nism behind the solar cycle. A meridional flow of plasma over the
sun s surface from equator to poles carries the relics of sunspots
north and south. At the poles the cooling material sinks down into
the body of the sun as far as the base of the convective zone, and
then migrates back toward the equator. But the magnetic scars left
by sunspots linger on through this cycle, ghosts that seed the next
generation of active regions.
Mikhail described the complicated relationship of sun, Earth,
and humanity.
Even in historical times the sun s variability has affected the
Earth s climate. For more than seventy years, from around 1640 to
1710, very few sunspots were observed on the sun s face and the
Earth was plunged into what the climatologists call the Little Ice
Age. Europe suffered severe winters and cool summers; at the
peak of it, in 1690, London children ice-skated on the Thames.
In the electronic age, a growing dependence on high technology
made humans much more vulnerable to even mild solar tantrums.
In April 1984 a flare knocked out communications on Air Force One;
President Reagan, over the mid-Pacific, was left incommunicado for
two hours. Before June 9 the most intense storm on record had oc-
curred in September 1859; that one had melted telegraph wires.
7 4 " C L A R K E & B A X T E R
We actually came close to that again in 2003, Mikhail said.
The sun suffered two eruptions in successive days, aimed right at
the Earth. We were saved from more severe effects only by a chance
alignment of magnetic fields.
Rose Delea was getting restless. All these phenomena are well
known.
Mikhail said, Yes, we think we are getting a handle on mea-
suring the effects of these different solar glitches and predicting
them, though that s still more an art than a science . . . He put up a
slide of three space weather scales that the current Space Weather
Service had inherited from the old American Space Environment
Center, and had elaborated on since. You can see we describe three
types of problem for Earth: geomagnetic storms, solar radiation
storms, and radio blackouts. Each type is calibrated with these
scales, from one to five one being minor, and five being severe.
Siobhan nodded. And June 9
June 9 was principally an outcome of a coronal mass ejection,
and would be measured by our G-scale, our geomagnetic-storm
scale.
And its rating?
Off the scale. June 9 was unprecedented. But the irony is that
the event was better predicted than any solar glitch in history,
thanks to Doctor Mangles. He glanced at Eugene.
But Eugene, as distracted as ever, didn t react to the cue; he
seemed barely aware that the rest of the group existed.
There was an awkward silence. Bud called for a break.
You had to fetch your own coffee, it turned out; there were no spare
hands to fetch and carry. And there were no digestive biscuits, not
one on the whole damn Moon.
A line quickly formed at the coffee spigot at the back of the
room. But Mikhail, near the front of the queue, picked up two
plastic beakers of coffee and tentatively approached Siobhan, who
accepted a beaker gratefully. Mikhail s face was lugubrious and
crumpled, and his voice was warm and rich; Siobhan liked him in-
stinctively.
S U N S T O R M " 7 5
He said, I imagine you re the first Astronomer Royal to visit
the Moon?
You know, I don t think any of us even left Earth before.
Flamsteed would be proud of you.
I like to think so. She sipped her coffee, and couldn t help but
grimace.
He smiled. I apologize for Clavius coffee. And for the recep-
tion you ve received here. We Moon-folk are an odd lot. A small
society.
I was expecting a certain insularity.
But it s more than that, Mikhail said. We are very self-
reliant we have to be. But that breeds a certain indifference to out-
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