Mission sunward: better forecasting for solar storms

If the family friend in "The Graduate" had been a solar physicist, his career advice to young Ben might have been "Just two words: magnetic fields."

They're the driving force behind the sun's most powerful storms. They wreak havoc with satellites, trigger blackouts, disrupt communications and navigation equipment, and endanger astronauts.

This weekend, an international mission to gather the most detailed information yet on the sun's magnetic fields is slated for launch in Japan. The goal is to gather information that will help improve scientists' ability to forecast the storms with enough lead time to mitigate the damage on Earth.

"All the explosive events on the sun are driven by the release of magnetic energy," says John Davis, a solar physicist with NASA's Marshall Space Flight Center in Huntsville, Ala., and project scientist for the three-year mission, known as Solar B. "You have to be able to measure the magnetic fields to see how much energy is stored in them and where and when it's released."

In the past, he adds, scientists have taken crude measurements of these fields, which arc all over the sun's surface. Early instruments only allowed scientists to measure the motions of these fields along their line of sight. One could tell if the fields were leaving or reentering the sun's surface, but that represents an incomplete picture, Dr. Davis continues.

Researchers have come to learn that the energy in these fields builds when they stretch and twist – much like a rubber band. Solar storms erupt when a large field gets too energetic for its own good and becomes unstable. The twisting or shearing can pinch off a vast bubble of magnetic field and send it – and any hot electrically charged gas trapped in it – hurtling into space. Once these "coronal mass ejections" (CMEs) are launched, the remnant magnetic field left behind reconnects with the sun's surface, triggering another burst of energy called a solar flare.

For Earth, the bad news comes when one of these roiling bubbles of magnetism couples with the planet's magnetic field. This adds energy to Earth's field and also can squeeze it. Satellites that once enjoyed Earth's magnetic field's protection from streams of charged particles coming from the sun suddenly find themselves outside the walls of the fort.

Current sun-studying satellites far from Earth can spot a CME as it leaves the sun, recording when it passes by. But these give relatively little lead time to shut down satellites temporarily, adjust their orbits, or prepare power grids for a surge.

Solar B is designed to capture the additional dynamics of the sun's magnetic fields in visible light, as well as extreme ultraviolet light and X-rays. This trio should allow scientists "to track the effects of these magnetic fields all the way through the sun's atmosphere," Davis says. The results eventually could help extend forecast lead times once scientists discover more-subtle signals on the sun's surface.

The mission comes at a time when the sun itself, and solar science, are undergoing mini-eruptions of their own.

The sun is entering the upswing to a new sunspot cycle, when solar activity is expected to grow more intense. And solar science is unbolting its training wheels and emerging as a basic-research enterprise in its own right, notes Nancy Crooker, a research scientist at Boston University's Center for Integrated Space Weather Modeling. Next year kicks off the first International Heliophysics Year, an international effort to study sun-solar system interactions.

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