About GRAPES-3

About GRAPES-3

  • The Gamma Ray Astronomy PeV EnergieS phase-3 experiment is located at TIFR’s Cosmic Ray Laboratory in Ooty in Tamil Nadu.
  • It is a collaboration of the Indian Tata Institute of Fundamental Research, the Japanese Osaka City University and the Japanese Nagoya Women’s University.
  • GRAPES-3 (Gamma Ray Astronomy PeV EnergieS phase-3) is designed to study cosmic rays with an array of air shower detectors and a large area muon detector.
  • It aims to probe acceleration of cosmic rays in the four astrophysical settings.
  • The experiment had earlier detected the effect of a solar storm that hit the earth in June 2015.
  • The muon telescope has been successfully used to study acceleration of muons during large thunderstorm events.
  • GRAPES-3 also has an important role in understanding the propagation of storms from the L1 point (Lagrange point) to its impact on the Earth.

Note: Lagrange Points are positions in space where the gravitational forces of a two body system like the Sun and the Earth produce enhanced regions of attraction and repulsion.


How potential of thundercloud was measured using GRAPES-3?

  • Clouds have negative charges along their lower side and positive charges on top and can be several kilometres thick. However, thunderstorms last only for about 15-20 minutes, which makes it difficult to calculate the potential of thundercloud.
  • Muons and other particles are produced when cosmic rays bombard air particles surrounding the earth.
  • The muons produced can have positive or negative charge.
    • When a positively charged muon falls through a cloud, it loses energy. If its energy falls below 1 giga electron volt (GeV), which is the threshold of detection of the GRAPES-3 muon telescope, it goes undetected.
    • When a negatively charged muon falls through a cloud, it gains energy and gets detected.
  • Since there are more positive than negative muons produced in nature, the two effects don’t cancel out, and a net change in intensity is detected.
  • The researchers monitored the profiles of the clouds using four ground-based electric field monitors.
  • Only the cloud that crossed on December 1, 2014, had a profile that was simple enough to simulate.
  • Using a computer simulation and the observed muon intensity variations, the researchers worked out the relationship with the electric potential of the cloud.
  • They calculated that the potential of the cloud they were studying was approximately 1.3 GV, which no one has ever measured potential, size and height of a thundercloud simultaneously.


Way ahead

  • This method in future can be used to understand the terrestrial gamma ray bursts (huge flashes of light that accompany lightnings).
  • Learning about the properties of thunderclouds can be useful in navigation of aircraft and preventing short circuits. This serendipitous discovery might provide the means to making headway in this direction.



Section : Science & Tech
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