The GRAPES-3 moun telescope located at the Cosmic Ray Laboratory (CRL) in Ooty, India recorded a massive burst of galactic cosmic rays about 20 GeV, on 22 June 2015 lasting for 2 hours. Report says the burst temporarily caused a severe compression of Earth’s magnetosphere from 11 to 4 times the radius of Earth, and it triggered a severe geomagnetic storm that supercharged aurora borealis, and radio signal blackouts in many high latitude countries in North and South America.
The source of the cosmic ray burst was a giant cloud of plasma ejected from the solar corona, which traveled at a speed of about 2.5 million kilometers per hour and eventually struck the planet’s magnetosphere. Magnetosphere is what makes the earth a habitable place, and if its magnetic field becomes ineffective, it would mark the end of the world. This vast region surrounding the planet extends over a radius of a million kilometers and it protects us from high intensity energetic radiations such as solar winds and galactic cosmic rays.
The data the team from the Tata Institute of Fundamental Research in India obtained by performing numerical simulations based on the GRAPES-3 data indicated that the Earth’s magnetic shield temporarily cracked due to the occurrence of magnetic reconnection.
Magnetic reconnection can occur in any place where ionized gas called plasma are present. The plasma contains magnetic field lines which under normal circumstances don’t break or merge with other field lines. However, the geomagnetic storm that was taken place was so powerful that it forced the fields lines to get close to each other, causing reconfiguration of our magnetic shield and eventually allowing the lower energy galactic cosmic ray particles to slip through our atmosphere. The magnetic field then bent these particles about 180 degree from the day-side to the night-side of the Earth where it was detected as a burst at the mid-night of 22 June 2015.
Transient Weakening of Earth’s Magnetic Shield Probed by a Cosmic Ray Burst – Physical Review Letters
The GRAPES-3 tracking muon telescope in Ooty, India measures muon intensity at high cutoff rigidities (15–24 GV) along nine independent directions covering 2.3 sr. The arrival of a coronal mass ejection on 22 June 2015 18:40 UT had triggered a severe G4-class geomagnetic storm (storm). Starting 19:00 UT, the GRAPES-3 muon telescope recorded a 2 h high-energy (∼20 GeV) burst of galactic cosmic rays (GCRs) that was strongly correlated with a 40 nT surge in the interplanetary magnetic field (IMF). Simulations have shown that a large (17×) compression of the IMF to 680 nT, followed by reconnection with the geomagnetic field (GMF) leading to lower cutoff rigidities could generate this burst. Here, 680 nT represents a short-term change in GMF around Earth, averaged over 7 times its volume. The GCRs, due to lowering of cutoff rigidities, were deflected from Earth’s day side by ∼210° in longitude, offering a natural explanation of its night-time detection by the GRAPES-3. The simultaneous occurrence of the burst in all nine directions suggests its origin close to Earth. It also indicates a transient weakening of Earth’s magnetic shield, and may hold clues for a better understanding of future superstorms that could cripple modern technological infrastructure on Earth, and endanger the lives of the astronauts in space.