Video: Rethinking space weather

Electron disturbances in the upper atmosphere. Terrestrial weather as well as solar activity may be exerting an influence on this region. (Image: NASA/GSF)

WHETHER it’s showering spacecraft with lethal radiation, filling the sky with ghostly light, or causing electrical surges that black-out entire cities, space weather is a force to be reckoned with.

Thankfully, all is calm in space on the day that I speak to Bill Murtagh at the US National Oceanic and Atmospheric Administration in Boulder, Colorado. “Last week we saw a moderate storm, and that was about the most interesting event in months,” he reassures me. “It’s pretty quiet today.”

And Murtagh should know – his job is to forecast space weather, which comprises any disturbance in near-Earth space, including the upper reaches of the Earth’s atmosphere where satellites roam. Many of the serious events involve disturbances in the charged portion of the atmosphere, known as the ionosphere, which stretches from 80 to 1000 kilometres above sea level. The finger of blame has always been pointed at the sun, which bombards the Earth with a stream of charged particles in the form of the solar wind. During the last three years, though, the sun’s cycle of activity has hit a trough, and as Murtagh observes, space weather is temporarily calm.

Yet if the sun really is the only cause, things haven’t been quite as quiet as we might have expected. Despite the solar lull, activity in the ionosphere still hots up occasionally – with ghostly tides of charged particles that throw GPS systems out of whack and block radio communication. It seems that as much as one-fifth of this space …