Does Cosmic  -ray flux vary during total solar eclipse (TSE) ? A random walk through TSEs

1. Does Cosmic-ray flux vary during total solar eclipse (TSE) ? A random walk through TSEs PRANABA K NAYAK On behalf of TIFR Mumbai and J.C. Bose Institute Kolkata

2. -ray flux at observational level • Cosmic ray origin • Terrestrial Origin

3. Variation of -ray flux during normal days

4. Observation at Diamond Harbour IUCDAEF, Kolkata Bose Institute, Kolkata On 24th October 1995 TSE

5. 1 August 2008 Total Solar Eclipse Started at northern Canada and extended up to Xi’an of China before crossing Greenland, the Arctic, central Russia, Mangolia and China. Over this period of 2 hours, the shadow of moon traveled along an arc of about 10000 kms and covered 0.4 % of the surface area of the earth. The duration of the totality reached its maximum value of 2m 27 sec at Nadym over a path of 237 km and 0.51 km/s.

6. BINP, Novosibirsk: The venue of observation Novosibirsk, a Russian city falling on the path of the totality can see it with time period of about 2m 18 s. Budker Institute of Nuclear Physics (BINP) is located just at the outscots of Novosibirsk thought to be an ideal location. Requirement of UPS, about 600 kgs of lead-bricks and radioactive sources for calibration was met by BINP

7. Novosibirk observation on 1 August, 2008 • Construction of a tent to avoid direct sunlight • NaI(Tl) detectors are large volume and identical • Exactly similar signal processing • Data collected on the eclipse day from four hours before to one hour after the end of eclipse.

8. Trend in atmospheric parameters on 1 August 2008 • Temperature started decreasing at the time of first contact • Minimum temperature 10 min after totality. Max decrease 10 0C • Pressure data shows negligible variation (~0.3%) • Humidity also showed significant drop during the eclipse and some recovery after the eclipse

9. Variation in -ray flux and its reproducibility • Excellent correlation between data from two detectors • Observed variations are reproducible • Small statistical error • Just prior to eclipse, a drop in flux of about 4 % with sudden increase in flux of about 9% • Throughout the eclipse, steady decline of flux of about 4 %

10. Comparison with data from other experiment • Short-term decrease prior to eclipse • Recovery prior to the last contact • Earlier worker observed recovery, in a rather steady manner, before the last contact • Our data did not show any recovery even two hours after the last contact Eclipse of 11 August 1999

11. Single location measurement • Influence of atmospheric and local phenomenon may play a significant role in generating observed variation Important proposals for next observation • Has to be carried out at two widely separated locations along the path of totality with identical detectors and signal processing equipment • Data should be taken for atleast one week prior to one week after the eclipse day

12. 22 July 2009 Total Solar Eclipse • The TSE begins in India and passes through Bangladesh, China, Japan’s Ryukyu Islands and moves through the Pacific ocean where the maximum totality duration reaches 6 min 39 s • A partial eclipse was seen with much broader path including eastern Asia and Pacific Ocean Total solar eclipse on 22 July 2009 As the Earth will not experience such high duration totality for next more than a century, it was termed as Eclipse of the Century

13. 22 July 2009 total solar eclipse in India Considering accessibility of excellent infrastructure facilities at RRCAT and NB University, it was decided to carryout TSE experiments at Indore and Siliguri

14. Variation in -ray flux in three different days

15. Sensitivity of the NaI(Tl) detector system to rain Detectors are very much sensitive to rain Even a rainfall in the order of 1 x 10-2 inch per 4 minutes can increase the -ray flux significantly From the long term studies, it was observed that the -ray flux enhancement subsidises to normal within a time span of 75-90 minutes, after the rain episode It is reasonable to consider that any data 90 minutes after the last rain episode is genuine, without any contribution from rain-induced radioactivity

16. Variation in atmospheric parameters on 22 July 2009 at RRCAT Pressure almost remains constant throughout Temperature remains rangebound between 24-28 0C Relative humidity was very high of above 85 % throughout There was rain after the totality and continued even after the end of eclipse Except for rainfall, there is no major changes in the atmospheric parameters during the period of eclipse

17. Observation before and during the totality

18. Observation by other group 22 July 2009 R. Bhattacharya et al., Current Science, 98 (2010) 1609

19. Observation of -ray flux variation from eclipse to eclipse 11 Aug 1999 24 October 1995 1 Aug 2008 22 July 2009 22 July 2009

20. Annular eclipse of 15 January 2010 Similar to Novosibirsk experiment More uncertainty A. Bhaskar et al., Astropartcle Physics 35 (2011) 223

21. Summary • Gamma ray flux varies during total solar eclipse • Magnitude of variation is not consistent from one TSE to another • We are well equipped for understanding this phenomena • Need to carryout more number of experiments for establishing the fact • However, this depends on frequency of TSEs

22. Future total solar eclipses till 2020 Except 2017 TSE, all other TSEs will spend most of time in water

23. Directions of future studies ! • Wait till 2017 TSE in USA ? • Develop collaborations and systematic for attempting in water ? • Suggestions ! Thank you !Thank you very much !