TeV Cosmic-ray Anisotropy &

Tibet Yangbajing Observatory

Qu XiaoboInstitute of High Energy Physics

ARGO HallTibet AS array

Yangbajing Observatory

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 rayLarge scale anisotropy

OUTLINE

• Large scale anisotropy in sidereal time

• Energy dependence • Time evolution• Models

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

Energy dependence Sidereal time anisotropy

Amenomori, APJ, 2005

Harmonic analysis

“East-west”(E-W) subtraction method

increase

independent

decrease

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

Anisotropy expected by CR production and propagation

(R – rigidity)(δ ~ 0.3-0.6 )

Important probe, discover CR origin, study CR propagation.

Diffusion model: The amplitude of anisotropy

increase with the energy!

1. Random character of SN explosions;

2. Mixed primary mass composition;

3. Possible e ect of the single source;ff

4. The Galactic Halo;

Sidereal time anisotropy

Tail-In max. shifts earlier in the south

Tail-In

Loss-Cone

Tail-In

Loss-Cone

Hall et al. (JGR, 104, 1999)

Hall et al. (JGR, 103, 1998)

Structure analysis NFJ model

Tail-in

Loss-cone

Gaussian analysis

Zenith

On-source

Off-sourceOff-source

,on onI N N

Ion

on

N

Ioff

off

——Global fitting method

2on on

2

2

2

1on on off,i off,in

N I -<N/I> i2on 2 21

on on off,i off,ini

N I - N I

χ =N I + N I

2 2,

,t on

t on

Equal

,off offI N

Two dimension analysis method

Zenith belt

The CR anisotropy is fairly stable in two samples.

Three Componets ：I--------Tail-in;II-------Loss-coneIII------Cygnus region ；

Tibet measurement in two dimensions

<<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

4 TeV

6.2 TeV

12 TeV

50 TeV

300 TeV

Celestial Cosmic Ray intensity map in five energy range

<12TeV Energy independent >12TeV Fade away

“Tail-in” effect exists in 50TeV, rule out the solar causation.

Energy dependence

Sidereal time anisotropy by ARGO

1.5TeV

0.7TeV

3.9TeV

Median energy

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

Energy dependence

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

Sidereal time anisotropy in 9 Phases (1999-2008)

<<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

Stable Insensitive to solar activitiesImproved analysis method, more statistic.

Temporal Variations

Time Evolution of the Sidereal Anisotropy

The fundamental harmonicincrease in amplitude with time.

Milagro observation

No steady increase

Matsushiro Observation

Tibet Observation

1999-2008

2000-2007

Sidereal time anisotropy in two hemisphere

Tibet IIIIcecube

Sidereal time anisotropy in Galactic coordinate

Tibet III

Icecube

Cosmic ray flows in three directions

Inward flowsOutward flowsElectrically neutral state

Excess

X.B.Qu et al., arXiv:1101.5273

Magnetic field induced by Cosmic ray flows

Extend the anisotropy imageobserved in the solar vicinity to the whole Galaxy.

30

4 r

rlIdBd

Biot-Savart Law

A0 dynamo model J.L. Han,19971. 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

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

Global +Midscale Anisotropy

Two intensity enhancements along a

Hydrogen Deflection Plane

Hydrogen Deflection Plane

uni-directional flow +bi-directional flowLocal interstellar magnetic field

Residual anisotropy after subtracting In,m

In,mIn,m(GA)

In,m(MA)

Residual anisotropy after subtracting In,m(GA)

LIMC (Local Interstellar Magnetic Cloud) modelLocal 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

Alternative Model of the Sidereal time anisotropy

Known origin of large scale anisotropy

—— Compton-Getting Effect

Δ I< I >

= ( + 2 ) v c　 cos

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

Due to the solar motion around galactic center j E-

8

V=220km/s,

Expected dipole effect

We could observe

Expected

Expected Amp= 0. 16%

The statistic error 0. 026% ， ~5σ rule out the Compton-Getting effect.

Celestial Cosmic Ray intensity map for 300 TeV

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.

Δ I< I >

= ( + 2 ) v c　 cos

Due to terrestrial orbital motion around the Sun

j

8

E-

V=30km/s,

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

Known origin of large scale anisotropy

—— Compton-Getting effect

Differential E spectrum :

The amplitude is ~0.04%

——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 I

With the compton-getting effect subtracted.The amplitude ～ 0.04%.

——Additional effect (4TeV)

Tibet measurement in solar time II

Preliminary

Periodicity search in 3 energy ranges

Solar diurnal.Compton-Getting effect Sidereal-diurnal

Sidereal semi-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.

中意 ARGO 实验大厅

中日 AS 探测阵列

365.2422364.2422T Solar day

365.2422367.2422T= Solar day

Anisotropy Observations in other periods

Anti sidereal time

Ext-sidereal time

No signal is expected, the amplitude observed is within statistic error.

银河系磁场强度为 3uG 时

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．

银河宇宙线在磁场中传播

Cygnus 方向

回旋半径

3TeV 对应 0.001pc (200AU)

——NFJ model

zoh_N

zoh_V

zoh_S

-0.1

0

0.1

lia_2N

zoh_2S

lia_N

lia_V

0 6 12 18 24 30 36 42 48

lia_S

57.0N

34.5N

11.2N

8.2S

4.4N

36.2S

14.7S

57.6S

zoh_N

zoh_V

zoh_S

-0.1

0

0.1

lia_2N

zoh_2S

lia_N

lia_V

0 6 12 18 24 30 36 42 48

lia_S

57.0N

34.5N

11.2N

8.2S

4.4N

36.2S

14.7S

57.6S

Sidereal time anisotropy components

Nagashima, Fujimoto, Jacklyn (JGR, 103, 1998) Hall et al. (JGR, 103, 1998)

Tail-In

Loss-Cone

Tail-In max. shifts earlier in the south

One-dimensional observation Sidereal time anisotropy

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 ，经测量

,2.01.0 GVPu 25100

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

宇宙线及大尺度各向异性

Medium scale anisotropy

Milagro

ARGO

Tibet-III

Large scale anisotropyMilagro

Tibet-III