Last night the sun unleashed a flash of radiation called a solar flare, along with a generous belch of ionized matter that is now racing toward Earth at thousands of kilometers a second. The solar storm front from the ionized blast, called a coronal mass ejection (CME), should arrive tomorrow morning, according to the National Oceanic and Atmospheric Administration's Space Weather Prediction Center (SWPC). The forecasters called the event the strongest solar storm since 2005.*
When a solar storm hits Earth, the impact can have a number of consequences, especially in Earth orbit and at high latitudes, where the planet's geomagnetic shielding is thin. Solar storms can knock out satellites, cause blackouts and force aircraft to avoid polar routes. Storms can also bring the aurora borealis, aka the northern lights, down to unusually low latitudes. (You can see a slideshow of recent low-latitude auroras here.)
The SWPC is forecasting that the inbound storm will reach G2 ("moderate") and possibly G3 ("strong") levels on the geomagnetic storm scale, which tops out at G5. A G3 storm should not cause severe problems for satellite operators or power companies but could interrupt satellite-based navigation systems and some radio communications. Such storms can also produce auroras visible as far south as Illinois and Oregon, according to the SWPC.
Researchers predict that the coronal mass ejection should reach Earth around 9:00 A.M. (Eastern Standard Time) on Tuesday, January 24. But that timeline is a bit uncertain; SpaceWeather.com notes that the storm could hit up to seven hours sooner or later than that. It should continue into the following day, according to SWPC forecasts, so auroras could be visible Tuesday night in North America.
* UPDATE (5:20 P.M., 1/24/2012): NOAA says the geomagnetic storm from the CME has only reached G1 ("minor") levels but that the storm of radiation is now the strongest since 2003.