The Mighty Gannon Storm Strikes
Imagine the Sun throwing a temper tantrum so epic that it sends a barrage of charged particles hurtling toward Earth. That’s exactly what happened on May 10-11, 2024, when the Gannon storm—dubbed the Mother’s Day storm—hit our planet. This geomagnetic superstorm was the most powerful event of its kind in over two decades. Dr. Atsuki Shinbori and his team from Nagoya University took this opportunity to study the storm’s impact on Earth’s plasmasphere, a protective shell of charged particles. Their findings, published in Earth, Planets and Space, shed light on how such storms can disrupt satellites, GPS, and communications.
The Arase satellite, launched by JAXA in 2016, was in the perfect spot to capture the action. As the storm raged, it provided continuous data on the plasmasphere’s dramatic contraction. The storm pushed this protective layer to a record low altitude, offering scientists a rare glimpse into the storm’s ferocity and its aftermath.
Plasmasphere Takes a Hit
The plasmasphere, working in tandem with Earth’s magnetic field, acts as a shield against harmful cosmic rays and solar particles. Normally, it extends about 44,000 kilometers above Earth. But during the Gannon storm, it was squashed to a mere 9,600 kilometers. This drastic reduction was caused by solar eruptions that sent billions of tons of charged particles our way.
Within nine hours, the plasmasphere shrank to one-fifth of its usual size. Its recovery was painstakingly slow, taking over four days—the longest since Arase began its mission in 2017. Dr. Shinbori noted that intense heating near the poles initially caused a drop in charged particles, complicating the plasmasphere’s recovery. This prolonged disruption can mess with GPS accuracy and satellite operations, making space weather forecasting even trickier.
Auroras Brighten Unexpected Skies
The storm’s intensity was so great that it shifted auroras far from their usual polar homes. Normally confined to the Arctic and Antarctic circles, auroras made surprise appearances in mid-latitude regions like Japan, Mexico, and southern Europe. This is because the storm compressed Earth’s magnetic field, allowing charged particles to travel further along magnetic lines.
These unexpected light shows were a treat for those in areas that rarely witness such phenomena. Stronger geomagnetic storms like Gannon can push auroras closer to the equator, offering a dazzling display in places where they’re typically a no-show.
Negative Storms and Their Impact
About an hour after the Gannon storm hit, a surge of charged particles flowed through Earth’s upper atmosphere, heading towards the poles. As the storm waned, the plasmasphere slowly began to refill with particles from the ionosphere. Typically, this process takes a day or two, but this time it stretched to four days due to a ‘negative storm’.
Negative storms occur when intense heating alters atmospheric chemistry, reducing oxygen ions and slowing the plasmasphere’s recovery. Such storms are invisible, detectable only by satellites. Dr. Shinbori’s research highlighted how these negative storms prolong recovery by disrupting particle supply—a phenomenon not clearly observed before.
Facts Worth Knowing
- •💡 The Gannon storm compressed Earth’s plasmasphere to just 9,600 km above the surface.
- •💡 Auroras appeared in Japan, Mexico, and southern Europe due to the storm’s intensity.
- •💡 Negative storms can prolong plasmasphere recovery by altering atmospheric chemistry.
