NOAA’s Space Weather Prediction Center (SWPC) — a division of the National Weather Service — is monitoring the sun following a series of solar flares and coronal mass ejections (CMEs) that began on May 8.
Space weather forecasters have issued a Severe (G4) Geomagnetic Storm Watch for the evening of Friday, May 10. Additional solar eruptions could cause geomagnetic storm conditions to persist through the weekend.
A large sunspot cluster has produced several moderate to strong solar flares since Wednesday at 5:00 am ET. At least five flares were associated with CMEs that appear to be Earth-directed. SWPC forecasters will monitor NOAA and NASA’s space assets for the onset of a geomagnetic storm.
CMEs are explosions of plasma and magnetic fields from the sun’s corona. They cause geomagnetic storms when they are directed at Earth. Geomagnetic storms can impact infrastructure in near-Earth orbit and on Earth’s surface, potentially disrupting communications, the electric power grid, navigation, radio and satellite operations.
SWPC has notified the operators of these systems so they can take protective action. Geomagnetic storms can also trigger spectacular displays of aurora on Earth.
According to NOAA, a geomagnetic storm is a major disturbance of Earth’s magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth. These storms result from variations in the solar wind that produces major changes in the currents, plasmas, and fields in Earth’s magnetosphere.
The solar wind conditions that are effective for creating geomagnetic storms are sustained (for several to many hours) periods of high-speed solar wind, and most importantly, a southward directed solar wind magnetic field (opposite the direction of Earth’s field) at the dayside of the magnetosphere.
This condition is effective for transferring energy from the solar wind into Earth’s magnetosphere.
The largest storms that result from these conditions are associated with solar coronal mass ejections (CMEs) where a billion tons or so of plasma from the sun, with its embedded magnetic field, arrives at Earth. CMEs typically take several days to arrive at Earth, but have been observed, for some of the most intense storms, to arrive in as short as 18 hours.
During storms, the currents in the ionosphere, as well as the energetic particles that precipitate into the ionosphere add energy in the form of heat that can increase the density and distribution of density in the upper atmosphere, causing extra drag on satellites in low-earth orbit.
The local heating also creates strong horizontal variations in the in the ionospheric density that can modify the path of radio signals and create errors in the positioning information provided by GPS.
While the storms create beautiful auroras, they also can disrupt navigation systems such as the Global Navigation Satellite System (GNSS) and create harmful geomagnetic induced currents (GICs) in the power grid and pipelines.