NASA said in a press release this week that twin spacecraft providing long-view, 3-D images of the sun might help provide better warning about solar storms, particularly events called coronal mass ejections (CMEs).
These torrents of ionized gas and magnetic field energy can weigh billions of tons and stretch to many times the size of Earth. When these solar hurricanes come into contact with our planet’s atmosphere, they can damage satellites, interfere with radio communications and cell phones, and knock out power grids on the ground, as they did on March 13, 1989, leaving six million Canadians without power. (Besides wrecking havoc, CMEs also produce dazzling displays known as the aurora borealis or australis, the northern and southern lights.)
To better understand the mass and structure of these stellar ejecta and track their velocity, NASA has turned to the dual STEREO (Solar TErrestrial RElations Observatory) satellites. Launched in 2006, the spacecraft "bracket" Earth, with one traveling in front of the planet and the other trailing behind in their orbits around the sun. This arrangement, rather like the spacing of our eyes (making Earth the schnoz in this analogy), allows for depth perception, ergo 3-D. Just as this ability helps us discern movement and direction, so, too, will STEREO provide astronomers with eyes in the sky to accurately follow the solar outbursts.
At present, the forecasting ability for CMEs is spotty. The BBC reports that STEREO should improve astro-meteorological predictions because the twin spacecraft should allow scientists to better say which CMEs may actually strike Earth as well as give them a better sense of when. This early warning system, which may provide notice up to 24 hours in advance is important not only for the planet's satellite fleet, whose craft can individually prepare by powering down or changing their orientation, but also for astronauts in the International Space Station, and doubly so for spacewalking astronauts, whose spacesuits only offer protection from normal levels of space radiation. The powerful radiation of CMEs can damage DNA and tissue, increasing the risk of cancer, for instance.
Right now the sun is in the most dormant phase (so-called solar minimum) of its 11-year sunspot cycle. More sunspots mean stormier stellar climes, although it is clear sailing for the time being. However, activity should ramp up by around 2013, when the STEREO project and space weather monitoring systems based on it should have their work cut out for them with a bounty of solar hurricanes to track.
The twin STEREO spacecraft keeping watch over the sun in an artist's conception. Image credit: NASA