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

-ray flux at observational level

Cosmic ray origin

Terrestrial Origin

Variation of -ray flux during normal days

Observation at Diamond Harbour

Bose Institute, Kolkata

IUCDAEF, Kolkata

On 24th October 1995 TSE

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.

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

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.

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

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 %

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

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

22 July 2009 Total Solar Eclipse

Total solar eclipse on 22 July 2009

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

As the Earth will not experience such high duration totality for next more than a century, it was termed as Eclipse of the Century

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

04:00 08:00 12:00 16:00 20:00

96

98

100

102

104

No

rma

lize

d r

ate

(%

ge

)

IST (h)

July12th09 July20th09 July24th09

Variation in -ray flux in three different days

It is reasonable to consider that any data 90 minutes after the last rain episode is genuine, without any contribution from rain-induced radioactivity

Sensitivity of the NaI(Tl) detector system to rain

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

Even a rainfall in the order of 1 x 10-2 inch per 4 minutes can increase the -ray flux significantly

Detectors are very much sensitive to rain

00:00 04:00 08:00 12:00 16:00 20:00 24:00

0

2

4

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8

Time in hours (IST) --->

Ra

in r

ate

in m

m

85

90

95

Re

l.hu

m. (%

ge

)

21

24

27

Te

mp

in d

eg

.

725

750

775

Pre

ssu

re in

mm 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

Variation in atmospheric parameters on 22 July 2009 at RRCAT

Observation before and during the totality

Observation by other group

R. Bhattacharya et al., Current Science, 98 (2010) 1609

22 July 2009

Observation of -ray flux variation from eclipse to eclipse

22 July 2009

22 July 2009

1 Aug 2008

11 Aug 199924 October 1995

Annular eclipse of 15 January 2010

A. Bhaskar et al., Astropartcle Physics 35 (2011) 223

Similar to Novosibirsk experiment

More uncertainty

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

Future total solar eclipses till 2020

Except 2017 TSE, all other TSEs will spend most of time in water

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 !