• For the first time in the world, researchers at the GRAPES-3 muon telescope facility in Ooty have measured the electrical potential, size and height of a thundercloud that passed overhead
  • At 1.3 gigavolts (GV), this cloud had 10 times higher potential than the previous record in a cloud.
  • This is not because clouds with such high potentials are a rarity, but rather, because the methods of detection have not been successful so far.

Tell us about the Cloud structure

  • Clouds have negative charges along their lower side and positive charges on top and can be several kilometres thick.
  • If balloons are used to measure the potential difference between the top and bottom, they will take hours to traverse the distance.
  • Unfortunately, thunderstorms last only for about 15-20 minutes, and this method fails.

What about the Threshold of detection?

  • 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.
  • This method can be used to solve a 25-year-old puzzle of terrestrial gamma ray bursts — huge flashes of light that accompany lightnings, but which have not been explained in theory until now.
  • 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.