(MENAFN- The Arabian Post)

A super-charged solar storm known as the“Gannon event” forced the Earth's plasmasphere-a doughnut-shaped shell of charged particles that normally envelops the planet-to shrink to roughly one-fifth of its usual size, exposing satellites, communications networks and power infrastructure to elevated risks. Scientists tracking the process say the collapse was rapid and the recovery slowed significantly, offering a rare window into how extreme space weather reshapes our planet's protective magnetosphere.

On 10 and 11 May 2024, a cluster of coronal mass ejections triggered the most intense geomagnetic storm in two decades. Data reveals the plasmapause boundary retreated from around 44,000 kilometres above Earth to approximately 9,600 kilometres in under nine hours. The inner region contracted with unprecedented speed. The timing of the shrivelled plasmasphere and slow refill-taking more than four days to approach normal density-was captured in direct satellite measurements for the first time.

Dr Atsuki Shinbori of the Institute for Space-Earth Environmental Research at Nagoya University explained that the combined observations from the Japanese satellite Arase and a network of global GPS receivers revealed both how drastically the plasmasphere compressed and why its“refilling” process lagged. He noted that“while most storms cause the plasmasphere to compress to L-shell ~4 or 5, this one plunged to L~1.5 and then languished for a long recovery.”

The broader implications are stark. As the plasmasphere collapsed, the ionosphere underwent what is described as a“negative storm” phase-a region-wide depletion of electron density that can severely impair GPS positioning and radio propagation. Ground-based TEC measurements revealed a strong enhancement in high latitudes shortly after storm onset, followed by widespread depletion during the recovery phase.

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Satellite-borne instruments and ground stations documented widespread auroras extending to unusually low latitudes including parts of Australia and Florida, confirming that charged particles were penetrating deeper into the magnetosphere than in typical disturbances. One expert likened the event to“flushing the bath-when the magnetosphere contracts, particles that would normally remain trapped near the equator can surge toward the ground or into satellite orbits.”

The storm's arrival coincided with sustained high-speed solar wind streams and strong southward interplanetary magnetic field components, driving an SYM-H index minimum near –518 nT and Kp reaching 9-benchmarks of a G5-class superstorm. In the scientific journal Earth, Planets and Space, the event is characterised as having“timescales of plasmaspheric refilling much longer than any CME-driven storm within the Arase era.”

Researchers warn that the increasing reliance on satellite-based navigation, communications and Earth-orbit infrastructure means events such as this one are more consequential than ever. More than 5 000 satellites reportedly had to adjust their orbits to avoid decaying prematurely during the storm window. The incident underscores the need for improved forecasting models that account not just for the immediate solar ejecta but for the slow asymmetry of recovery in the plasmasphere-ionosphere system.

Still, the storm also generated a rich trove of scientific data. The detailed in-situ electron density profiles captured by Arase and global TEC maps provide an unprecedented basis to refine 3-D models of plasmaspheric dynamics. One modelling study found the plasmapause had shifted to L≈1.5 within nine hours of onset and required more than four days to recover to half the pre-storm electron density baseline-a recovery period more than twice that seen in many previous strong storms.

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