Doughnut of fire. A computer-generated visualization of the ring current (blue). The red rings at the poles represent the particles' contribution to the aurora.

Earth's Friendly Fire

When a space storm whips up, Earth becomes enveloped by high-energy ions that can damage satellites and even interfere with electronics on the ground. Now, new satellite data show that most of those nefarious ions originate in our planet's own protective atmosphere.

A space storm starts with a gust of particles flowing from the sun. Earth's magnetic field deflects this solar wind, but not before it blows oxygen ions from the atmosphere into space. These ions and particles from the solar wind then collect in a long tail of magnetic fields stretching away from Earth. The tail occasionally snaps back, surrounding Earth in a vast doughnut-shaped cloud of particles called the ring current. Particles from the ring current then rain down, creating a hazard for satellites. But how much of the ring current originates in the solar wind, and how much comes from ions blown out of the atmosphere, has been an open question.

Now, NASA's Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) has given researchers their first bird's-eye view of entire space storms, and the new vantage makes clear that Earth's atmosphere plays an active role. IMAGE's orbit takes it high above the North Pole, far enough away to watch tons of oxygen ions flow out into space, collect in the magnetic tail, and boomerang back. As it turns out, these oxygen ions make up most of the ring current, IMAGE researchers reported on 9 May at a press conference at NASA headquarters in Washington, D.C.

IMAGE data could be a boon to researchers developing computer models to forecast space weather, says Terry Onsager of the National Oceanic and Atmospheric Administration's Space Environment Center in Boulder, Colorado: "This kind of result will help us to understand ... what kind of measurements we need to look at to feed our models more accurately."

Related sites
The IMAGE Web site
The Space Environment Center Web site
Space weather forecasts at SpaceWeather.Com