How did Earth react during the super solar storm of 2024? A study to predict malfunctions of satellites, GPS, and communications networks during extreme space weather events.
A geomagnetic superstorm is an extreme space weather phenomenon that occurs when the Sun emits enormous amounts of energy in the form of radiation and charged particles, known as the “solar wind“. When these particles reach Earth, they can disrupt its magnetic field, generating geomagnetic storms. Superstorms are rare: they occur on average once every 20-25 years.
Gannon’s Storm. On May 10 and 11, 2024, the Earth was hit by the most intense superstorm in the last two decades, known as “TGannon storm (in memory of Jennifer Gannon, physicist specialized in Space Weather)” or “TMother’s Day storm”.
A study led by Atsuki Shinbori of Nagoya University’s Institute for Space-Earth Environmental Research has recorded for the first time direct and detailed measurements of how the superstorm affected the “plasmasphere,” a region of Earth’s magnetosphere composed of cold plasma (ions and electrons) that surrounds Earth and extends beyond the upper atmosphere, following magnetic field lines. It is one of the natural shields that surround the Earth.
The results, published in the journal Earth, Planets and Spaceshow how the plasmasphere and ionosphere — the layer of the atmosphere rich in charged particles — reacted during the violent solar storm. This information is crucial for predicting possible malfunctions in satellites, GPS and communications networks during extreme space weather events.
in the right place at the right time. The Arase satellite, launched by JAXA (the Japanese Space Agency) in 2016, regularly passes through the plasmasphere measuring plasma waves and magnetic fields. During the May 2024 superstorm, he found himself in an ideal position to closely observe the drastic compression and slow recovery of the plasmasphere, recording data never obtained before.
For the first time, in fact, scientists were able to continuously and directly observe the plasmasphere shrinking to an exceptionally low altitude due to a superstorm.
«Thanks to Arase and the GPS receivers on the ground» – explains Shinbori – «we monitored the plasmasphere and ionosphere simultaneously. This allowed us to understand how much the plasmasphere shrank and why its recovery was so slow.” Under normal conditions the plasmasphere extends up to approximately 44,000 km above the Earth’s surface. During the storm, its outer boundary collapsed to just 9,600 km, a compression equal to a fifth of its usual size.
A hyperactive Sun at the origin of the superstorm. The storm was caused by a series of large solar flares (coronal mass ejections) that hurled billions of tons of charged particles into space.
In just nine hours the plasmasphere was compressed in an exceptional way and took over four days to recover: the longest recovery period ever observed since Arase has been monitoring this layer since 2017.
«We discovered» – Shinbori reports – «that the storm initially intensely heated the atmosphere near the poles, and then caused a drastic drop in charged particles in the ionosphere. This has slowed the reconstruction of the plasmasphere, with potentially serious effects on GPS, satellites and communications.”
Spectacular auroras at unusual latitudes. During the strongest phase of the storm, the Earth’s magnetic field was compressed enough to allow solar particles to push much closer to the equator. The result was an exceptional increase in the aurora borealis, visible in regions where they usually do not appear.
Auroras are typically seen near the poles, where Earth’s magnetic field funnels solar particles into the atmosphere. But the power of the superstorm pushed the “auroral zone” as far as Japan, Mexico and southern Europe, places where these phenomena are very rare.
THE “negative storm”. About an hour after the start of the superstorm, large quantities of charged particles in the upper atmosphere were transported towards the poles. When solar activity began to decrease, the plasmasphere began to rebuild thanks to particles coming from the ionosphere. It normally takes a day or two for the plasmasphere to return to its usual size.
In this case the recovery lasted four days, due to a phenomenon called “negative storm“: a sudden decrease in particles in the ionosphere due to chemical changes caused by strong atmospheric warming. During a negative storm, the amount of oxygen ions that help transport the hydrogen particles needed to fill the plasmasphere decreases. In practice, oxygen ions modify the local electric and magnetic fields that help protons (H⁺) to rise in the plasmasphere. These are invisible phenomena, detectable only by satellite instruments.
«The negative storm» – underlines Shinbori – «slowed down the recovery by altering the chemistry of the atmosphere and reducing the influx of particles. Such a clear link between negative storm and recovery delay has never been observed before.”
How the Earth reacts. During the May superstorm, several satellites suffered electrical problems, data interruptions, GPS signal disturbances, and radio communications interference. Understanding how long it takes for the plasmasphere to recover after such violent events is essential to improving space weather predictions and protecting the technologies on which communications, navigation and Earth observation depend.