When a solar storm hits Earth, we often think of spectacular auroras. But, Beyond the light show, these explosions of energy from the Sun directly impact in an almost invisible region that protects our planet: the plasmasphere.
This “shell” of plasma, a gas made up of charged particles, surrounds the Earth and acts as a silent extension of our magnetic field, filtering out radiation and dampening some of the bombardment of particles arriving from space. Without the plasmasphere, satellites, communications and even our own technological environment would be much more fragile.
Normally, this layer extends up to about 44,000 kilometers above the Earth’s surface, forming a spherical structure that cooperates with the magnetosphere to block dangerous particles. But a new study, published in Earth Planets and Space and led by Atsuki Shinbori of Nagoya University, shows that a geomagnetic superstorm can reduce it to a fraction of its original size.
And that’s exactly what happened on May 10 and 11, 2024, during the most powerful event in the last two decades: the so-called Gannon storm. The key to this discovery is the Arase satellite, launched by the Japanese space agency (JAXA) in 2016 and located in a perfect orbit to study the plasmasphere. During the May superstorm, Arase was literally in the right place at the right time.
As the Earth received a wave of billions of tons of charged particles from several coronal mass ejections, Arase recorded how the plasmasphere was brutally compressed. from the usual 44,000 km… to just 9,600 kilometers. That is, it shrank to about 20% of its normal size in just nine hours. Never before had something like this been observed continuously and directly.
“We were able to track changes in the plasmasphere with Arase, and at the same time monitor the ionosphere from the ground. “That allowed us to see not only how much it contracted, but why it took so long to recover.”Shinbori explained in a statement.
After extreme compression, it would be logical that the plasmasphere would begin to fill with particles from the ionosphere, a lower layer of the atmosphere that acts as a “depot” to replenish it. But this time it didn’t happen like that. The study reveals that the recovery lasted more than four days, the longest period ever observed since Arase began its mission in 2017. The reason? A phenomenon known as a negative storm.
During the most intense phase of the event, the upper atmosphere became so hot that it altered the chemistry of the air, dramatically reducing the amount of oxygen ions and, with them, the production of hydrogen particles that normally fill the plasmasphere. The result was a “blackout” of particles that left the plasmasphere practically without supply.
“The negative storm slowed the recovery by modifying atmospheric chemistry and cutting off the source of particles that the plasmasphere needs to expand – concludes Shinbori -. This link (negative storm and delayed recovery) has never been observed so clearly”.
This simultaneous contraction of the plasmasphere and compression of the Earth’s magnetic field had another spectacular effect: The auroras descended towards latitudes where they almost never appear.
The storm moved the auroral belt from the polar regions to areas as far south as Japan, Mexico and southern Europe, visual evidence of the enormous stress to which the magnetosphere was subjected. But The consequences were not left in heaven. During the storm, several satellites suffered electrical failures, some temporarily stopped transmitting data, and GPS and radio communications problems were reported.
Although these extreme events occur every 20 to 25 years, scientists warn that understanding exactly how the plasmasphere compresses and recovers will be vital to anticipating future risks. This study not only offers the most detailed observation of a superstorm affecting the plasmaspherebut also opens a crucial window to protect space-dependent technological infrastructure.