Are We Ready for the Next Solar Maximum? No Way, Say Scientists
Richard A. Kerr
Forecasters testing their skills against the sun's mounting ferocity find
themselves still in the early days of space weather prediction.
The Big One for space physicists struck on 28
August 1859. The sun had blasted a billion-ton
magnetic bubble of protons and the like right at
Earth. On smashing into the planet's own
magnetic cocoon at several million kilometers
per hour, the bubble dumped its energy, pushing
the solar-driven aurora from its customary arctic
latitudes to overhead of Cuba. This once-in-500years "solar superstorm" crippled telegraph
systems for a day or two across the United
States and Europe but otherwise was mainly
remembered for its dramatic light show.
Solar assailant. The sun violently
Now that our world has evolved into a so-called
ejects magnetically confined
cyberelectrosphere of modern electronics, we
bubbles of charged particles (left)
can hardly hope to fare as well. Today, the
that collide with Earth's magnetic
charged-particle radiation and electromagnetic
field (right), triggering geomagnetic
fury of a geomagnetic superstorm would fry
storms.
satellites, degrade GPS navigation, disrupt radio
communications, and trigger continent-wide
CREDITS: SOHO (ESA & NASA)
blackouts lasting weeks or longer. Even a storm
[Larger version of this image]
of the century would wreak havoc. That's why
space physicists are so anxious to forecast
space weather storms accurately. If predicting a
hurricane a few days ahead can help people prepare for a terrestrial storm's onslaught,
they reason, predicting solar storms should help operators of susceptible systems
prepare for an electromagnetic storm.
And space weather forecasters' next challenge is coming up soon. The next peak in the
11-year sunspot cycle of solar activity looms in 2012 or 2013. A space weather
symposium* last month asked, "Are we ready for Solar Max?" The unanimous answer
from participants was "No." "I think we are better off " than a decade ago, says space
physicist Daniel Baker of the University of Colorado, Boulder. Back then, researchers
were about to launch their first concerted effort to predict space weather the way
meteorologists predict terrestrial weather, using computer models. "But we probably
aren't as ready as we ought to be," Baker adds.
In fact, space forecasters are about where their meteorological colleagues were in the
1960s: making useful but unimpressive forecasts in the short term and lacking computer
models able to improve on longer-term predictions by human forecasters. And even the
short-term forecasts could go by the boards if the sole but aging early-warning satellite
fails before a replacement—as yet unfunded and unplanned—arrives in orbit.
High-tech target
While researchers have been working to improve their forecasting skills, the world has, if
anything, become more susceptible to space weather. "The general trend would be
increasing vulnerability to the effects of space storms," says Baker, who chaired a
December 2008 workshop report on the subject by the Space Studies Board of the U.S.
National Academies. "In general, the systems are becoming softer." The power grid
operates more efficiently, he says, but that gives it less margin for error and less
capacity to buffer a storm's disruptions. The surging power-line currents induced by a
severe solar storm could push the grid into uncharted territory. GPS technology,
especially the highest-precision variety, has become commonplace since the last solar
maximum—for navigating planes more autonomously, for example—but it comes with
new codes and new signals untested by the ionospheric disturbances of a major solar
storm. Now-ubiquitous cell phones are no less vulnerable.
The academies' report put a huge price tag on a repeat of the 1859 superstorm. Judging
by the costs of smaller incidents in recent decades, the panel estimated the economic
cost in just the first year after such an extreme storm at $1 trillion to $2 trillion. Full
recovery would take 4 to 10 years. Disturbances in the high-altitude ionosphere would
disrupt radio communications and GPS for days; surges induced in the power grid could
destroy expensive and hard-to-replace transformers. Satellites that survived could cost
$100 million apiece to put back into operation. Even a recurrence of the lesser
superstorm of May 1921 could lead to blackouts affecting 130 million Americans and
half of North America, the panel reported.
Status quo
If you pity the poor weatherman, then your sympathies for the space weather forecaster
should be unbounded. In May 1996, Ernest Hildner—then director of the National
Oceanic and Atmospheric Administration's Space Environment Center in Boulder,
Colorado—told an audience that when it comes to predicting space weather, "we don't
do very well. We're several decades behind weather forecasters."
A big part of the problem, Hildner said, was a dearth of observations. Space weather
forecasters used ground-based telescopes to observe sunspots, solar flares, and other
signs that the sun was primed to launch solarstorm-inducing disturbances toward Earth.
But forecasters had no spacecraft between the sun and Earth to record the passage of
threatening solar disturbances, much less whether they were actually going to hit Earth.
It was "like predicting Washington, D.C., weather with one weather station in San
Francisco," Hildner said.
Enter ACE. In 1997, the Advanced Composition Explorer arrived at its station, L1 or
Lagrangian point 1, about 1.5 million kilometers sunward of Earth. There it could monitor
the high-speed bubbles of protons and other charged particles—called coronal mass
ejections (CMEs)—that would slam into the bulbous end of Earth's teardrop-shaped
magnetosphere 30 to 60 minutes after passing ACE. The speed and density of a CME
reflects its total energy. But ACE also reports the orientation of the magnetic field
embedded in a CME, which must be opposite that of Earth's magnetic field if the CME's
power is to gain entry to the magnetosphere and drive a storm.
ACE made the first short-term storm warnings possible in 1999. Issued only 20 to 60
minutes ahead of a storm's arrival by the Space Weather Prediction Center (SWPC, the
former Space Environment Center), the warnings have fallen far short of perfection.
One-third of major storms arrive unheralded and almost one-quarter of the warnings turn
out to be false alarms, according to SWPC's own analysis. More severe storms are so
rare that it's hard to say how much skill forecasters have in predicting them, says
Christopher Balch, acting head of SWPC's forecast office.
ACE can offer no help with forecasting storms a day ahead. Next-day SWPC forecasts
of geomagnetic activity based on observations of the sun have performed better than
simply assuming that the current day's conditions would persist into the next day. But
next-day forecasts performed no better than if forecasters assumed the next day would
be like the average of the previous 30 days. Accurate forecasting 8 hours to 1 day
ahead, Baker concludes, "is just not in the cards right now."
Playing catch-up
To push useful space weather forecasting beyond a few minutes ahead, geophysicists
are emulating terrestrial weather forecasters. From the 1950s onward, meteorologists
built and refined computer models that ingested a torrent of observations and produced
a picture of current weather around the globe. The models could then calculate how the
weather would evolve. Over several decades, the models surpassed human forecasters
at short-range prediction and pushed useful forecasts out beyond 7 days.
Space weather forecasters face extra hurdles. There's
still a severe dearth of observations to feed into the
models. And rather than evolving within one relatively
uniform atmosphere, space weather progresses from
the near-vacuum of a million-degree solar corona—
where magnetic fields rule—to Earth's relatively
dense, cold upper atmosphere and eventually the
ground: "sun to mud," as they say. That forces
researchers to develop a dozen submodels to make a
chain linking the sun to Earth. Space scientists hoping
to transfer their research models to the forecasting
arena should "expect to have your egos hurt,"
magnetospheric physicist W. Jeffrey Hughes of
Boston University (BU) said at the May meeting of the
American Geophysical Union. "It's a painful process."
To ease the pain of moving from research modeling to
day-to-day forecasting, the American space weather
community has developed a loose structure for
creating and testing forecast models. Two 8-year-old
centers—one at the University of Michigan (UM), Ann
Arbor, and the other an 11-institution consortium
headed by BU—vie in friendly competition to develop
physics-based, sun-to-Earth models. A 10-year-old
interagency modeling center at NASA's Goddard
Space Flight Center (GSFC) in Greenbelt, Maryland,
is evaluating 30 contributed submodels. Finally, a test
bed will soon be created at SWPC for debugging
candidate submodels before they go operational.
Coming out blazing. The
sun (masked here to reveal
faint features) will be blasting
more coronal mass ejections
(lower right) Earth's way as
the sun enters its next cycle
of rising activity.
CREDIT: SOHO (ESA &
NASA)
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No model—not even a submodel—has made it through this system to operational
status. A submodel called ENLIL is leading the pack, says SWPC Director Thomas
Bogdan. ENLIL forecasts how newly formed CMEs will propagate from the sun to ACE.
But it won't become operational for 2 to 3 years, around the time of solar max, when it
will be run on the same supercomputer National Weather Service forecasters use.
Models carrying the disturbance into and through the magnetosphere and the
atmosphere and to the ground all trail ENLIL.
"We've made very good progress in the last decade," says space physicist Tamas
Gombosi, director of the UM modeling center. "But can we forecast? No. We have a
long way to go. My hope is that not this solar max but the next, physics-based
forecasting" will be a reality.
In the meantime, scientists are keeping their fingers crossed for ACE. At 12 years old, it
has entered satellite old age. It and the 14-year-old SOHO satellite that images CMEs
near the sun "can fail any time, no one knows," notes Michael Hesse, director of the
modeling center at GSFC. Although enough time remains to build and launch a backup
for ACE's monitoring system, none has been proposed, much less funded.