13 December 2010

X-ray vision: Space weather and the Solar Dynamics Observatory

Posted by mohi

However serene it may seem to sunset-watching romantics, the Sun’s surface is an explosion of activity. Solar flares, ejections of plasma, and solar storms regularly spew energy and charged particles into interplanetary space.

These violent disturbances sweep through space and can knock out satellites and global positioning systems (GPS), radio communications, and electrical power grids on earth. A plane in mid-flight during a solar flare can lose GPS connection and communication with ground crews, a situation in which no pilot wants to be. Predicting solar activity, scientists believe, would help power grid operators and airlines protect their crews, passengers, and equipment.


An artist's rendition of the Solar Dynamics Observatory, courtesy of NASA

In February, NASA launched the Solar Dynamics Observatory (SDO), an Earth-orbiting spacecraft, dedicated to investigating the Sun and it’s effect on Earth and space weather. At this AGU meeting, teams are presenting some of the observatory’s early findings.

One of the three instruments on board, the Extreme Ultraviolet Variability Experiment (EVE) is measuring sunlight in the far ultraviolet to X-ray area of the spectrum. Cissi Ying-tsen Lin, an engineer at Virginia Tech, presented the poster “Soft X-Ray Energy Detection from Broadband Images by the Solar Aspect Monitor on Solar Dynamic Observatory” in the session “SH11B: Solar and Heliospheric Physics.” She and her colleagues at Virginia Tech and the University of Colorado have developed a way to image the smallest wavelengths of the spectrum, the wavelengths that indicate the most forceful eruptions.

She’s captured these X-rays through a pinhole camera on the SDO. By separating the incoming photons, ranging between 0.1 nanometers to 7 nanometers in wavelength, she can create an image of the high-intensity solar events and illuminate an area of the Sun’s X-ray light that we couldn’t see before.

Researchers hope this additional data will help them to reliably predict solar storms. Solar weather prediction, however, is still in it’s infancy. And, so far, the greater detail is revealing that there is a lot of progress to be made.

The Sun’s magnetic fields are threaded across the solar surface in a complex net. The ever-changing dynamics of the magnetosphere determines where and when storms, flares and plasma ejections will occur. While
the Earth’s magnetosphere is a relatively simple dipole, the Sun’s magnetosphere resembles a swirled mass of yarn in constant flux. An eruption in one location is tied to eruptions across the Sun’s entire surface. How this works, though, is still a mystery.

The sunset-watching romantics should remember that solar storms are not exclusively bad news. Their effects can also be beautiful. The aurora borealis–colorful swirling lights seen in the sky at near-pole latitudes–is a response to fluctuations in the Earth’s ionosphere from solar events. A solar forecast may one day allow aurora enthusiasts to plan romantic sky-watching nights, just in case they missed the sunset.

–Danielle Venton is a science communication graduate student at UC Santa Cruz