• The GRAPES-3 experiment is a special telescope-array established in Ooty to detect muons from cosmic ray showers.
• The experiment has detected a surge in muon intensity correlated with a weakening of the earth’s magnetic field due to a solar storm that hit the earth.
• An Indo-Japanese collaboration, this experiment is unique in that it can be used to study solar storms and space weather at distances up to two times the earth’s radius, unlike satellite-based studies that can yield information only about what is happening in their vicinity.
• A coronal mass ejection (CME) left the sun on June 21, 2015 and, along with two such others that left the sun on June 18 and 19, reached earth on June 22, 2015. Solar flares are often followed by CMEs which are nothing but giant clouds of plasma which also contain embedded magnetic fields. This CME was associated with a solar flare from the sunspot region 12371 near the central disc of the sun.
• This caused a solar storm and ensuing radio blackouts and Aurora Borealis. Analysing data from the GRAPES-3 muon-tracking telecope, scientists have inferred that while it lasted, the CME resulted in weakening the earth’s magnetic field, allowing high energy cosmic rays to burst through.
• This method can serve as a monitor of solar storms.
• “Galactic cosmic rays producing a muon burst were bent in the space surrounding the Earth over a volume that is 7 times that of the Earth, and hence they serve as a monitor of the solar storm over this volume.
• This is in stark contrast to the satellite based measurements that provide only in situ information.

Source: The Hindu