U.S. space weather forecasters say the Earth on Thursday received a glancing blow from a "coronal mass ejection" (CME) – effectively, a solar eruption – first detected on the surface of the sun four days ago.
The U.S. National Oceanic and Atmospheric Administration (NOAA), the agency responsible for monitoring the weather for much of North America, also does its best to monitor "weather" in space.
NOAA Space Weather Prediction Center Lead Forecaster Bob Rutledge said space weather is, for the most part, solar activity. The forecasters use satellites and other Earth-based instruments to monitor what the sun is sending out. For example, solar wind consisting of protons and electrons in a state known as a plasma continuously flows out of the sun.
But during periods of high solar activity, Rutledge said, forecasters watch for CMEs, which can eject billions of tons of plasma and magnetic field material from the sun's corona. One such event was observed Sunday, and by its size and the rate of its speed as it left the sun, it was forecast to pass by the Earth on Thursday.
Rutledge said this was not a big event, and even if the full force of it hit the Earth, it would have minimal effect — a G-1 or less on their geomagnetic storm scale. At this level, such an event might cause some fluctuations on the power grid, possibly some minor effects on satellite operations, and maybe aurora borealis (northern lights) activity in northern latitudes.
Rutledge said that if this event were a G-5 — the top of the geomagnetic storm scale — there could be widespread blackouts or even collapse of the power grid; satellites could see problems with orientation or basic operations; navigation systems could be useless for a matter of days; and auroras could be seen as far south as Florida or other Southern U.S. states.
Rutledge said forecasters monitor minor events like Thursday's near miss so they can better predict much bigger events when they come.