GRAPES-3 Experiment

GRAPES-3 Experiment

For the first time in the world researchers at the GRAPES -3 muon telescope facility in Ooty have measured the electrical potential, size and site of a thundercloud that past overhead on December 1 2014.

GRAPES-3 Experiment:

• GRAPES-3 (Gamma Ray Astronomy Pev EnergieS Phase 3)  is designed to study Cosmic rays with an array of hair shower detectors and large area muon detector.
• It aims to probe acceleration of Cosmic rays in the following 4 astrophysical settings.
• It is located at Ooty in India and started as collaboration of the Tata Institute of fundamental research, Mumbai, India and the Osaka City University, Osaka, Japan.

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 approximately 1.3 giga volts.
• At 1.3 Gv this cloud 10 x higher potential than the previous record in a cloud.
• No one has ever measured potential, size and height of a thundercloud simultaneously.

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 kilometers thick.
• If balloons are used to measure the potential difference between the top and the bottom, they will take hours to transverse the distance.
• Uunfortunately, thunderstorms last only about 15 to 20 minutes and this method fails.

What are muons? how they are 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.
• Then A positively charged charged muon Falls through a cloud, it loses energy.
• If its energy Falls below 1 giga electron volt, which is the threshold of detection of the GRAPES-3 muon telescope, it goes undetected.
• On the contrary, negatively charged muon gains energy when falling through the cloud and gets detected.
• Since there are more positive and negative muons produced in nature, the two effects don't cancel out, and a net charge in intensity is detected.