does cosmic -ray flux vary during total solar eclipse (tse) ? a random walk through tses pranaba k...
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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
6
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 !