A crack in Earth s magnetic shield let galactic cosmic rays leak into the Earth s atmosphere and caused huge geomagnetic storms in the northern hemisphere.
The GRAPES-3 muon telescope in Ooty, India, detected a spike in cosmic ray levels, indicating that the Earth s magnetic shield may be damaged.
Though the burst of rays was recorded back in June 2015, a study just published in Physical Review Letters has revealed the extent of the high-intensity event for the first time.
For two hours on 22 June, 2015, particles from a giant cloud of fast-moving plasma penetrated the Earth s atmosphere.
The particles, which originated from the surface of the Sun, were moving at about 2.5 million kilometres per hour when they struck our planet s atmosphere.
This high-speed strike caused the Earth s magnetosphere – the area containing the planet s magnetic field – to shrink from 11 times to four times the Earth s radius.