TeV Cosmic-ray Anisotropy
&
Tibet Yangbajing Observatory
Qu Xiaobo
Institute of High Energy Physics
Yangbajing Observatory
Tibet AS array
ARGO Hall
The Tibet Air shower Array
– Located at an elevation of 4300 m
(Yangbajing , China)
– Atmospheric depth 606g/cm2
– Wide field of view (Dec. -15º,75º )
– High duty cycle (>90%)
– Angular resolution (~0.90)
Advantage----measurement of Cosmic ray
Large scale anisotropy
OUTLINE
• Large scale anisotropy in sidereal time
• Energy dependence
• Time evolution
• Models
• Compton-Getting effect
• Solar time anisotropy
• Periodicity
• Summary
Sidereal time anisotropy
Energy dependence
Harmonic analysis
decrease
increase
independent
Amenomori, APJ, 2005
“East-west”(E-W) subtraction method
Anisotropy expected by CR production and propagation
Diffusion model:
The amplitude of anisotropy
(R – rigidity)
(δ ~ 0.3-0.6 )
increase with the energy!
1. Random character of SN explosions;
2. Mixed primary mass composition;
A. D. Erlykin, A. W. Wolfendale, Astropart. Phys. 25, 183(2006)
3. Possible effect of the single source;
4. The Galactic Halo;
Important probe, discover CR origin,
study CR propagation.
Sidereal time anisotropy
Tail-in
Structure analysis
NFJ model
Tail-In max. shifts earlier in the south
Loss-cone
Hall et al. (JGR, 103, 1998)
Gaussian analysis
Loss-Cone
Tail-In
Loss-Cone
Tail-In
Hall et al. (JGR, 104, 1999)
Two dimension analysis method
Zenith
——Global fitting method
N on
Ion , Non
Zenith belt
Ion
On-source
Equal
Off-source
χ
2
on
=
 Non
Off-source
Ion -<N/I> 
2
2
Ioff , Noff
N off
Ioff


1
N
I
N
I
on
on
off,i
off,i 
n 

i

 
2
2
N on I on
+ n12  N off,i I off,i
i
 2   t2,on
t ,on
2
Tibet measurement in two dimensions
The CR anisotropy is fairly
stable in two samples.
Three Componets：
I--------Tail-in;
II-------Loss-cone
III------Cygnus region；
<<Anisotropy and Corotation of Galactic Cosmic Rays >>
M. Amenomori et al., Science, 314 429 (2006)
Large scale anisotropy in two dimension
Milagro
Super-Kamiokande-I
Also by ARGO, Icecube
Energy dependence
Celestial Cosmic Ray intensity map in five energy range
4 TeV
<12TeV Energy
independent
>12TeV Fade away
6.2 TeV
12 TeV
50 TeV
“Tail-in” effect exists in
50TeV, rule out the solar
causation.
300 TeV
Energy dependence
Sidereal time anisotropy by ARGO
0.7TeV
1.5TeV
3.9TeV
Median energy
Consistent with the 1D observations, finer structure in 2D
<<Observation of TeV cosmic ray anisotropy by the ARGO-YBJ experiment>> ICRC0814,2009
Temporal Variations
Sidereal time anisotropy in 9 Phases (1999-2008)
Improved analysis method, more statistic. Stable Insensitive to solar activities
<<On Temporal Variations of the Multi-TeV Cosmic Ray Anisotropy Using the Tibet III Air Shower Array >>,
M. Amenomori et al., ApJ 711, 119 (2010)
Temporal Variations
Time Evolution of the Sidereal Anisotropy
Matsushiro Observation
No steady increase
Tibet Observation
2000-2007
Milagro observation
The fundamental harmonic
increase in amplitude with time.
1999-2008
Sidereal time anisotropy in two hemisphere
Icecube
Tibet III
Sidereal time anisotropy in Galactic coordinate
Tibet III
Icecube
Excess
Cosmic ray flows
in three directions
Inward flows
Outward flows
Electrically neutral state
X.B.Qu et al., arXiv:1101.5273
Magnetic field induced by Cosmic ray flows
Extend the anisotropy image
observed in the solar vicinity
to the whole Galaxy.
 
 0 Idl  r
dB 
4 r 3
Biot-Savart Law
A0 dynamo model J.L. Han,1997
1. Magnetic Field Structure, Consistent
2. The extension of the local anisotropy to the whole Galaxy is reasonable.
X.B.Qu et al., arXiv:1101.5273
Alternative Model of the Sidereal time anisotropy
Global +Midscale Anisotropy
uni-directional flow +bi-directional flow
Local interstellar magnetic field
Two intensity enhancements along a
Hydrogen Deflection Plane
In,m(MA)
Hydrogen Deflection Plane
In,m(GA)
Residual anisotropy after subtracting In,m(GA)
Amenomori, M., et al. 2010, Astrophys. Space Sci. Trans., 6, 49
In,m
Residual anisotropy after subtracting In,m
Alternative Model of the Sidereal time anisotropy
LIMC (Local Interstellar Magnetic Cloud) model
Local Interstellar Cloud, egg-shaped cloud, 93 pc3.
Cosmic ray density (n) lower inside LIC than outside, adiabatic expansion
⊥Perpendicular
∥Parallel
LISMF
uni-directional flow (UDF) ⊥
bi-directional flow (BDF) ∥
Known origin of large scale anisotropy
—— Compton-Getting Effect
Due to the solar motion around galactic center
E-a
8
j
V=220km/s, a
ΔI
v
= ( a + 2 ) cos q
<I>
c
Expected dipole effect
We could observe
A.H. Compton and I.A. Getting, Phys. Rev. 47, 817(1935)
 2.7
Celestial Cosmic Ray intensity map for 300 TeV
Expected
Expected
Amp= 0. 16%
The statistic error 0. 026%，
~5σ rule out the ComptonGetting effect.
These results have an implication that cosmic rays in this energy
range is still strongly deflected and randomized by the Galactic
magnetic field in the local environment.
Known origin of large scale anisotropy
—— Compton-Getting effect
Due to terrestrial orbital motion around the Sun
E-a
8
Differential E spectrum : j
ΔI =(a+2) v
cos q
<I>
V=30km/s, a
D.J. Cutler, D.E. Groom, Nature 322, L434 (1986)
c
 2.7
Tibet measurement in solar time I
——Compton-Getting effect （12TeV）
The solar time
anisotropy is
stable in two
intervals with
different solar
activity
The 1D modulation
(solid line)
is consistent with the
expected one (dash
line)。
Tibet measurement in solar time II
——Additional effect (4TeV)
With the compton-getting effect subtracted.
The amplitude ～0.04%.
Periodicity search in 3 energy ranges
Solar diurnal.
ComptonGetting effect
Sidereal semi-diurnal
Sidereal-diurnal
<<Observation of Periodic Variation of Cosmic Ray intensity with the Tibet III Air Shower Array>>, A.-F. Li Nuclear Physics B,, 529, 2008.
Summary
•Yangbajing Observatory successfully observed the Cosmic ray
anisotropy.(0.7TeV-300TeV)
•Energy dependence, time evolution, Periodicity analysis of the
anisotropy
•In the sidereal time frame, revealing finer details of the
anisotropies components “tail-in” and “loss-cone” and “Cygnus”
region direction. Models given. origin???
•In the solar time frame, Compton-Getting effect is observed in
12TeV, An additional modulation appears to exist in case of low
energy.
中日AS探测阵列
中意ARGO实验大厅
Anisotropy Observations in other periods
T  365.2422
364.2422 Solar day
Anti sidereal time
T= 365.2422
367.2422 Solar day
Ext-sidereal time
No signal is expected, the amplitude observed is within statistic error.
银河宇宙线在磁场中传播
Cygnus方向
银河系磁场强度为3uG时
回旋半径
3TeV对应0.001pc (200AU)
带电粒子在传播过程中受磁场影响而偏离其原本方向．星际
磁场就像一个搅拌机，将宇宙线粒子搅拌得各向同性．
zoh_N
57.0N
zoh_V
34.5N
34.5N
11.2N
11.2N
4.4N
4.4N
zoh_2S
8.2S
8.2S
lia_N
14.7S
14.7S
lia_V
36.2S
36.2S
57.6S
57.6S
zoh_S
57.0N
lia_S
Sidereal time anisotropy components
——NFJ model
lia_2N
0.1
0
-0.1
18
0 24
6 30
1236
1842
2448
30
36
42
48
Nagashima, Fujimoto, Jacklyn (JGR, 103, 1998)
Hall et al. (JGR, 103, 1998)
Loss-Cone
Tail-In
Tail-In max. shifts earlier in the south
Sidereal time anisotropy
One-dimensional observation
宇宙线及大尺度各向异性
太阳时各向异性
低能处比较明显，随刚度幂律分布
存在截止刚度
  0.1  0.2, Pu  100 25GV
，经测量
随太阳活动有11年的周期变化，活动极小时，低至几
GV，极大时，可达200GV
最近观测发现，600GV宇宙线太阳时各向异性仍受到太阳活动
的调制；Tibet ASγ在4TeV处观测到超出CG效应的太阳时
各向异性，高能处与预期CG效应一致
Medium scale anisotropy
Milagro
ARGO
Tibet-III
Large scale anisotropy
Milagro
Tibet-III