Earth's magnetic field is about to be shaken like a snow globe by the largest solar storm in five years.
After hurtling through space for a day and a half, a massive cloud of charged particles is due to arrive and could disrupt utility grids, airline flights, satellite networks and GPS services, especially in northern areas. The same blast could also paint colourful auroras farther from the poles than normal.
Scientists say the storm, which started with a massive solar flare earlier in the week, is growing as it races outward from the sun, expanding like a giant soap bubble. When it strikes, the particles will be moving at 4 million mph.
"It's hitting us right in the nose," said Joe Kunches, a scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado. Astronomers say the sun has been relatively quiet for some time, and this storm, while strong, may seem fiercer because Earth has been lulled by several years of weak solar activity.
The storm is part of the sun's normal 11-year cycle, which is supposed to reach peak storminess next year. Solar storms don't harm people, but they do disrupt technology. During the last peak around 2002, experts learned that GPS was vulnerable to solar outbursts.
Because new technology has flourished since then, scientists could discover that some new systems are also at risk, said Jeffrey Hughes, director of the Centre for Integrated Space Weather Modelling at Boston University. A decade ago, this type of solar storm happened a couple of times a year, Mr Hughes said.
The sun erupted on Tuesday evening, and the most noticeable effects should arrive within hours, according to forecasters at the space weather centre. The effects could last until Friday morning. The region of the sun that erupted can still send more blasts our way, Mr Kunches said. He said another set of active sunspots is ready to aim at Earth right after this.
"This is a big sun spot group, particularly nasty," Nasa solar physicist David Hathaway said. "Things are really twisted up and mixed up. It keeps flaring." Storms like this start with sun spots, Mr Hathaway said.
Then comes an initial solar flare of subatomic particles that resemble a filament coming out of the sun. That part hits Earth minutes after the initial burst, bringing radio and radiation disturbances. After that comes the coronal mass ejection, which looks like a growing bubble and takes a couple of days to reach Earth. It is that ejection that could cause magnetic disruptions today.
Solar storms have three ways they can disrupt technology on Earth: with magnetic, radio and radiation emissions. This is an unusual situation, when all three types of solar storm disruptions are likely to be strong, Mr Kunches said. That makes it the strongest overall since December 2006.