The cosmic rays originated from the Sun's surface Getty / NASA

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. The charged particles in Earth’s magnetosphere usually deflect solar winds which would otherwise bring harmful ultraviolet radiation to the Earth’s surface.

Ultraviolet radiation – the same radiation that causes our skin to tan in the Sun – has been linked to higher incidences of cancer in pilots flying at high altitudes.

The solar wind also triggered a severe magnetic storm that brought down radio signals and sparked vivid northern lights across many countries in the north of the world. Analysis carried out by researchers working on the GRAPES-3 telescope indicated that for a short while, the Earth’s magnetosphere cracked, letting some low-energy galactic cosmic rays penetrate the atmosphere.

According to the study, the burst in cosmic activity indicated a “transient weakening of Earth’s magnetic shield”. Further research into the chance event may “hold clues for a better understanding of future superstorms that could cripple modern technological infrastructure on Earth,” the study’s authors write.