1. Observation of cosmogenic nuclide Be-7 concentrations in the air at Bangkok and trajectory analysis of global air-mass motion
S. Suzuki , H. Sakurai , F. Tokanai , E. Inui , H. Shimizu,
S. Kikuchi, Y. Kurebayashi,
K.Masuda,
W. Mitthumsiri, D. Ruffolo, R Macatangay

2. Introduction
Analysis the relationship between solar activities and cosmogenic nuclide.
Observation
Measured Be-7 concentration in the atmosphere at several locations.
We compared both.
Calculation of Be-7 production coming to Bangkok.
Be-7 movement by air circulation
Analysis backward trajectory by HYSPLIT and Box model
Simulation
Be-7 production at each location.
Estimated Be-7 production at arbitrary altitude and location using EXPACS

3. Cosmogenic nuclide Be-7
Cosmic ray collide with the atmospheric elements
Be-7 is produced
Be-7 attaches to aerosols
Aerosols with Be-7 fall down to the ground
Produced in the air
14 𝑁 (𝑛,𝑥) 7 𝐵𝑒 𝑁 (𝑝,𝑥) 7 𝐵𝑒
16 𝑂 (𝑛,𝑥) 7 𝐵𝑒 𝑂 (𝑝,𝑥) 7 𝐵𝑒
40 𝐴𝑟 (𝑛,𝑥) 7 𝐵𝑒 𝐴𝑟 (𝑝,𝑥) 7 𝐵𝑒
Decay
Detection
◎ We collected the aerosols and measured the Be-7 concentration

4. Observation of Be-7 in Bangkok
Sampler
13.765N, E
Sampling volumes
30 𝑚 3 /ℎ𝑜𝑢𝑟
Sampling location
Mahidol University
at Bangkok in Thailand
Ge detector at underground laboratory of the Intensity for
Cosmic ray Research in Tokyo University.

5. Time profiles of Be-7 concentrations from June 2014 to December 2016
High Be-7 concentrations (3.34) is during January and April.
Low Be-7 concentrations (1.44) is during May and December.
2.2 times
There is clear seasonal variation.

6. Back trajectories
HYSPLIT…The Hybrid Single Particle Lagrangian Integrated Trajectory Model We simulated back trajectories which is coming to Bangkok each one hour.
Conditions
Sampling location N, , 15m
Back time hours

7. Three back trajectories
Indian trajectories
May to September
Average altitude 1000m
Continental trajectories
October to February
Average altitude 3000m
Pacific Ocean trajectories
March to April
Average altitude 1000m

8. Concentration and back trajectories
During high Be-7 concentration
It is clear that there are three patterns in a year. The trajectory patterns are corresponded to the high and low concentrations in Bangkok.
During low Be-7 concentration

9. Calculation of the Be-7 production
EXPACS EXPACS can calculate the energy spectrum of neutron and proton at an arbitrary location.
Estimate of Be-7 production rate in an arbitrary altitude
P(h(t))
P(h(t))= 𝐸 1 𝐸 2 𝐹 𝑛,𝑝 𝐸,ℎ 𝑡 𝑁 𝑛,𝑜 𝑡 𝜎 𝐵𝑒−7 𝐸 𝑑𝐸
𝐹 𝑛,𝑜 𝐸,ℎ 𝑡 …Energy spectrum of neutron and proton at an arbitrary altitude
𝑁 𝑛,𝑜 𝑡 … A number of nitrogen or oxygen in air mass
𝜎 𝐵𝑒−7 … Cross section of Be-7 production
𝐸 1 , 𝐸 2 … Minimum, maximum energy (10MeV and 100GeV)
EXPACS

10. Calculation of the amount of Be-7 coming to Bangkok
altitude
〇Box model
𝑑𝑁(𝑡) 𝑑𝑡 =𝑃−λ𝑁 𝑡 −𝑘𝑁 𝑡 + 𝑘 𝑠𝑡𝑟 𝑁 𝑠𝑡𝑟 (𝑡)
P …production rate , N … the amount of Be-7
λ …decay constant , 𝑘 … removal rate
,where 𝑘 𝑠𝑡𝑟 =0:
∴　𝑁 𝑡 = 𝑃 λ+𝑘 𝑒 −(λ+𝑘)𝑡 　・・(1)
Monthly amount of Be-7 𝑁 𝑚𝑜𝑛𝑡ℎ 𝑥 is
𝑁 𝑚𝑜𝑛𝑡ℎ 𝑥 = 𝑡=0 𝑡=𝑥 𝑁(𝑡)
stratosphere
troposphere
𝑘 𝑠𝑡𝑟
scavenge
decay
Back trajectory x
Bangkok
Back time t
We compared between monthly amount of Be-7 𝑁 𝑚𝑜𝑛𝑡ℎ 𝑥 and observed Be-7 concentrations.

11. Comparison between simulated and observed Be-7
〇Simulated Be-7 shows a clear seasonal variation in a year as well as observed Be-7 concentrations.
〇Both rates of variability between high and low periods are similar.
〇Simulated Be-7 shows the time lag for one month from the observed Be-7 concentrations.
2.5 times
2.2 times

12. Yearly rate of variability
Be-7 at Bangkok
[mBq/m^3]
Simulated Be-7
[atoms/g]
Be-7 at Yamagata
Thule
[cnts/hour]
Princess Sirindhorn Neutron Monitor
Sun Spot number
2014
(From June to May)
2.29
247.1
4.9
4222
2.185× 10 6
94.4
2015
2.11
212.5
5.1
4298
2.190× 10 6
57.4
Rate(%)
-7.9
-14.0
4.1
1.8
0.2
-39.1
Observed Be-7 concentration and simulated Be-7 at Bangkok are decreasing.
Neutron monitors in Thule and Bangkok are increasing

13. Summary
Time profile of Be-7 concentrations at Bangkok shows a clear seasonal variation.
⇒ The high concentrations during January to April are 2.2 times as large as the low concentrations during May to December.
There are three kinds of patterns for the back trajectories coming to Bangkok.
We calculated the amount of Be-7 coming to Bangkok using the trajectory.
〇 Simulated Be-7 shows clear seasonal variation as well as Be-7 concentration
〇 There is time lag for one month between Simulated Be-7 and the observed Be-7 concentrations.
⇒In the future, we are going to have a calculation including the stratospheric components of Be-7 .