National Space Agency Issues Geomagnetic Storm Warning
The South African National Space Agency (SANSA) issued a three-day space weather alert on May 10th local time, warning of an impending G4-class solar storm that could potentially impact critical power grids and cause widespread voltage control issues.
Solar Flares Precede Storm
SANSA issued the alert after detecting three coronal mass ejections (CMEs) and intense solar flares earlier this week. The shockwaves from the CMEs are expected to merge before impacting Earth.
The U.S. Space Weather Prediction Center also issued a G4 geomagnetic storm warning on May 9th. This is the first time the center has issued a G4 warning—the second-highest on the five-step scale—since January 2005.
Coronal Mass Ejections
Coronal mass ejections are massive plasma explosions sometimes emitted by the Sun, which can send charged particles known as solar wind towards Earth.
Five such eruptions from the Sun's atmosphere are expected to occur, beginning late on May 10th and continuing into May 12th.
The culprit is a sunspot cluster visible on the right side of the Sun's disk, which is 16 times the size of Earth.
Geomagnetic Storms and Impacts
Geomagnetic storms can affect infrastructure in near-Earth orbit and on Earth's surface, potentially disrupting communications, power grids, navigation, radio wave propagation, and satellites.
The last time Earth experienced a G5 storm—the most severe on the scale—was in October 2003. That event caused damage to transformers in South Africa and power outages in Sweden.
The true strength of the storm will be known approximately 60-90 minutes prior to its arrival on Earth, thanks to satellites that measure directional energy bursts.
Summary
A G4-class solar storm is expected to impact Earth in the coming days. The storm is preceded by solar flares and coronal mass ejections, and it could cause disruptions to critical infrastructure and communications. The last time Earth experienced a similar storm was in 2003.