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TeV Cosmic-ray Anisotropy & Tibet Yangbajing ObservatoryPowerPoint Presentation

TeV Cosmic-ray Anisotropy & Tibet Yangbajing Observatory

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- 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

- Large scale anisotropy in sidereal time
- Energy dependence
- Time evolution
- Models

- Compton-Getting effect
- Solar time anisotropy
- Periodicity
- Summary

Energy dependence

Harmonic analysis

decrease

increase

independent

“East-west”(E-W) subtraction method

Amenomori, APJ, 2005

Anisotropy expected by CR production and propagation

Diffusion model:

The amplitude of anisotropy

(R – rigidity)

(δ ~ 0.3-0.6 )

increase with the energy!

- Random character of SN explosions;
- Mixed primary mass composition;
- Possible eﬀect of the single source;
- 4. The Galactic Halo;

A. D. Erlykin, A. W. Wolfendale, Astropart. Phys. 25, 183(2006)

Important probe, discover CR origin,

study CR propagation.

Tail-In max. shifts earlier in the south

Loss-Cone

Tail-In

Loss-Cone

Tail-In

Hall et al. (JGR, 104, 1999)

Tail-in

Structure analysisNFJ model

Loss-cone

Gaussian analysis

Hall et al. (JGR, 103, 1998)

Zenith

On-source

Off-source

Off-source

——Global fitting method

Zenith belt

Equal

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)

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

0.7TeV

1.5TeV

3.9TeV

Sidereal time anisotropy by ARGOMedian energy

Consistent with the 1D observations, finer structure in 2D

<<Observation of TeV cosmic ray anisotropy by the ARGO-YBJ experiment>> ICRC0814,2009

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)

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 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.

Biot-Savart Law

A0 dynamo model

J.L. Han,1997

- Magnetic Field Structure, Consistent
- 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)

In,m

Residual anisotropy after subtracting In,m(GA)

Residual anisotropy after subtracting In,m

Amenomori, M., et al. 2010, Astrophys. Space Sci. Trans., 6, 49

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

uni-directional ﬂow (UDF) ⊥

bi-directional ﬂow (BDF) ∥

LISMF

E-a

8

Δ I

< I >

v

c

= ( a+ 2 )

cos q

Known origin of large scale anisotropy——Compton-Getting EffectDue to the solar motion around galactic center

V=220km/s,a = 2.7

Expected dipole effect

We could observe

A.H. Compton and I.A. Getting, Phys. Rev. 47, 817(1935)

Celestial Cosmic Ray intensity map for 300 TeV

Expected

Expected

Amp= 0. 16%

The statistic error 0. 026%，

~5σ rule out the Compton-Getting 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

ΔI

< I >

v

c

= ( a+ 2 )

cos q

Due to terrestrial orbital motion around the Sun

Differential E spectrum :

j

E-a

8

V=30km/s,a = 2.7

D.J. Cutler, D.E. Groom, Nature 322, L434 (1986)

The amplitude is ~0.04%

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)

Preliminary

With the compton-getting effect subtracted.

The amplitude ～0.04%.

Periodicity search in 3 energy ranges

- Sidereal semi-diurnal

Solar diurnal.

Compton-Getting effect

- 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.

Anisotropy Observations in other periods

Anti sidereal time

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．

Sidereal time anisotropy components

——NFJ modelTail-In max. shifts earlier in the south

Tail-In

Nagashima, Fujimoto, Jacklyn (JGR, 103, 1998)

Hall et al. (JGR, 103, 1998)

One-dimensional observation

太阳时各向异性

宇宙线及大尺度各向异性

存在截止刚度 ，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

低能处比较明显，随刚度幂律分布

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