G5 geomagnetic storm hits Earth, first of its class in two decades

On 10 May 2024, a series of coronal mass ejections, huge clouds of charged particles thrown off the Sun, reached Earth and set off a geomagnetic storm rated G5. That is the highest level on the scale used by the US space weather forecasters at NOAA, and it was the first storm of that strength in about two decades.

The eruptions came from a very active sunspot region, and several of the clouds arrived close together, which strengthened the disturbance. Auroras, normally confined to high latitudes, were seen far to the south, including in Florida and Mexico, and were widely photographed across Europe, Asia and elsewhere.

The storm mattered beyond its visual spectacle. Forecasters warned of possible effects on power grids, satellites, radio communications and GPS navigation, and operators took precautions. Scientists also saw the event as a rare chance to study how the magnetosphere, Earth's magnetic shield, and the radiation belts around the planet respond to extreme space weather, which is the question later research such as Japan's Arase mission has pursued.