High above the surface, Earth’s magnetic field constantly deflects incoming supersonic particles from the sun. These particles are disturbed in regions just outside of Earth’s magnetic field – and some are reflected into a turbulent region called the foreshock. New observations from NASA’s THEMIS mission show that this turbulent region can accelerate electrons up to speeds approaching the speed of light. Such extremely fast particles have been observed in near-Earth space and many other places in the universe, but the mechanisms that accelerate them have not yet been concretely understood.
The GRAPES-3 muon telescope recorded a burst of galactic cosmic rays of about 20 GeV, on 22 June 2015 lasting for two hours. The burst occurred when a giant cloud of plasma ejected from the solar corona, and moving with a speed of about 2.5 million kilometers per hour struck our planet, causing a severe compression of Earth’s magnetosphere from 11 to 4 times the radius of Earth. It triggered a severe geomagnetic storm that generated aurora borealis, and radio signal blackouts in many high latitude countries.