OOTY: Even as the recent publication of the findings of the Cosmic Ray Laboratory (CRL) in Ooty on solar storm and its impact on the earth’s magnetic shield in 2015 has created ripples, here is a recapitulation of the extra terrestrial event that has rocked the scientific world. The CRL of the Tata Institute of Fundamental Research (TIFR) here recorded a geomagnetic storm, otherwise known as solar storm, which weakened the earth’s magnetic field, the shield which protects the planet from the invasion of the cosmic rays. When most parts of world was asleep on June 2, 2015, the ever vigilant team of scientists at the CRL witnessed showers of cosmic rays hitting the earth through the ‘muon tracking telescope’. ‘Muons’ are sub-atomic particles that are produced when the cosmic rays travel through the atmosphere. The CRL recorded a sudden burst of ‘muons’ indicating increase in cosmic ray intensity.
With its state-of-the-art high performance detectors, the ‘Grapes-3’ (Gamma Ray Astronomy at PeV Energies Phase-3), experiment at CRL could observe this rare activity. Dr Sunil K. Gupta, head of the CRL stated that the earth’s magnetic field (EMF) is aligned along north-south direction, and exerts its influence up to 50,000-km above the surface of the earth. The EMF acts as a shield by preventing the entry of most of the low energy cosmic rays into the atmosphere.
Though the cosmic rays continuously travel down to the earth, the low energy cosmic ray particles are bent by the EMF, and are sent back into space. But, the high energy cosmic ray particles which are small in number enter the earth’s atmosphere and get detected by the cosmic ray observatories across the world, he noted. “At the CRL in Ooty the scientists observed a sudden burst of cosmic ray activity on June 22, indicating that something had changed in the EMF above. Further studies showed that the burst of magnetized plasma from the sun, otherwise known as coronal mass ejection, which contains particles traveling with a high speed of thousand kilometers in a second, and having a low strength magnetic field in it, had affected the EMF. It is known that when the two magnets with their magnetic poles in opposite directions are brought close together, the magnetic field around it becomes weak.
A very similar thing happened on June 22, 2015, causing a geomagnetic storm by opening up weak spots in the EMF. This weakening of the EMF was about two per cent for two hours, as per the calculations of the CRL scientists, which paved the way for the invasion of cosmic ray particles during those two hours. They also found the margin of error to be below 0.1 per cent making it a very accurate study”, Dr Gupta explained.
However, as the solar storm moved past the earth, the EMF got restored back to its normal value after the said two hours. Only in the high altitude places on earth, nearer to the north and south poles, the disturbance to power lines and radio communication was noticed. As the coronal mass ejection from the sun takes nearly two days to reach the earth, the real ejection on sun had happened two days prior to the recording of cosmic ray muons in CRL, Ooty, he pointed out.
However, in case of a bigger solar storm in future the weakening of EMF could be much more, which would then adversely affect the functioning of the satellites, and other electrical and electronic devices on ground which can cause a major disruption. The ‘GRAPES-3’ due its location near the equator is relatively immune from such disruptions. The ‘Grapes-3’ offers the possibility to do ground-based studies of the same phenomenon from the safety of its location in South India, Dr. Gupta said and added that it took little more than a year to completely analyze and verify the data to publish a report on the said event.
CRL: A shining example of indigenous R&D
The Cosmic Ray Laboratory (CRL) of the Tata Institute of Fundamental Research (TIFR) in Ooty is the ‘numero uno” in its respective field in the world as its indigenous technology and related facilities along with large study area make it the best standing example for ‘make in India” concept too, said Atul Jain, scientist-in-charge of the CRL Ooty. He said that the ‘Grapes-3’ experiment was done in a world class lab designed to study cosmic rays. ‘Grapes-3’ is equipped with an array of 400 plastic scintillator detectors in a large area to detect the cosmic ray showers. Its ‘muon tracking telescope’ is the world’s largest such telescope which is known for its accuracy and superiority.
The cosmic ray detection process starts with plastic scintillator detectors, which receives the signals of cosmic ray showers. They are then processed at the modern cutting edge technologies and further simulated at the computing cluster. Finally, at the control room the signals are further analyzed to prepare the data, he explained. Mr Jain said that instrumentation, equipment and the electronics involved in the ‘Grapes-3’ experiment, wherein Japan is a collaboration partner, has been designed, developed and fabricated with indigenous in-house technology that has made CRL self-reliant and keeps it flag flying high in this field of fundamental research.
B.Srinivasa Rao, chief engineer and scientific officer at CRL said that to detect ‘muon’, the CRL designed near six meters hallow steel tubes, which are filled with inert gas and tungsten wires to receive ‘muonsignals’. As of now 3,200 such tubes have been placed in clusters in the CRL, which is protected by concrete slabs that filters cosmic rays but allows ‘muons’ enter the tube, he explained.
Stating that all the signals received from detectors placed across the CRL premises in Ooty is finally analyzed and studied at the control room, P.Jagadeesan, scientific officer at CRL said that the lab was functioning round the year without any break to record the cosmic ray and ‘muon signals’ from the outer space and to prepare data and to arrive at the inference.