GRAPES-3 Experiment: Gauging a Thunder C

Q. Why is this in news?

• For the first time in the world, researchers at the GRAPES-3 muon telescope facility in Ooty (short for Udhagamandalam) Tamil Nadu have measured the electrical potential, size and height of a thundercloud that passed overhead on December 1, 2014. 
• At 1.3 gigavolts (GV), this cloud had 10 times higher potential than the previous record in a cloud. 

Q. What is GRAPES-3 Experiment?

• 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 following four astrophysical settings.
• It is located at Ooty in India and started as a collaboration of the Tata Institute of Fundamental Research, Mumbai, India and the Osaka City University, Osaka, Japan.

Q. What is its principal area of research?

A.  Measuring the potential of a Thunderstorm

• Using a computer simulation and the observed Muon intensity variations, the group 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 Giga Volts.
• At 1.3 GV this cloud had 10 times higher potential than the previous record in a cloud.
• No one has ever measured potential, size and height of a thundercloud simultaneously.

Q. What might be Utility of this study?

• Learning about the properties of thunderclouds can be useful in navigation of aircraft and preventing short circuits.

Cloud structure are better assessed:

• Clouds have negative charges along their lower side and positive charges on top and can be several kilometres thick..

Q. What are Muons? How are they detected?

• 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.
• On the contrary, a negatively charged muon gains energy when falling through the cloud 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.