arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1407.2144astro-ph.HEhep-ex
收藏

$^{15}$ eV小于10的Cosmic Ray各向异性的观测

On the Observation of the Cosmic Ray Anisotropy below 10$^{15}$ eV

G. Di Sciascio, R. Iuppa

摘要:

测量宇宙射线到达方向上的各向异性与研究其能谱和化学成分是相辅相成的,有助于了解其起源和传播。它也是探测宇宙射线所穿过的磁场结构的工具。由于宇宙射线大多是带电的原子核,它们的轨迹在到达地球大气层之前会受到银河磁场的影响而发生偏转,因此它们的探测只能携带与其陀螺半径一样大的方向信息。如果考虑低于$10^{15}{\rm\,eV}$的宇宙射线,并考虑局部星系磁场($\sim3{\rm\,μG}$),则陀螺半径非常短,因此可以预期各向同性。最多可能存在弱偶极分布,反映最近CR源的贡献。然而,许多实验观察到恒星时间框架中的能量依赖性\emph{"large scale"}各向异性,振幅约为10 $^{-4}$ - 10 $^{-3}$,揭示了两个不同的宽区域的存在:在扬升右方,过剩的能量大约分布在40 $^{\circ}$到90 $^{\circ}$之间(通常称为“tail.in“过剩)和赤字(“损失锥”)150 $^{\circ}$至240 $^{\circ}$在Right Ascension。近年来,Milagro和ARGO-YBJ合作报告了尾部区域内的“中等”尺度各向异性。最近,南半球的冰立方实验也声称观测到了这样的小特征。到目前为止,还没有一个关于银河系中宇宙线的理论能够解释这些不同的各向异性的起源,而宇宙线的标准模型和银河系磁场的标准模型同时保持不变。

英文摘要:

The measurement of the anisotropy in the arrival direction of cosmic rays is complementary to the study of their energy spectrum and chemical composition to understand their origin and propagation. It is also a tool to probe the structure of the magnetic fields through which cosmic rays travel. As cosmic rays are mostly charged nuclei, their trajectories are deflected by the action of galactic magnetic field they propagate through before reaching the Earth atmosphere, so that their detection carries directional information only up to distances as large as their gyro-radius. If cosmic rays below $10^{15}{\rm\,eV}$ are considered and the local galactic magnetic field ($\sim3{\rm\,μG}$) is accounted for, gyro-radii are so short that isotropy is expected. At most, a weak di-polar distribution may exist, reflecting the contribution of the closest CR sources. However, a number of experiments observed an energy-dependent \emph{"large scale"} anisotropy in the sidereal time frame with an amplitude of about 10$^{-4}$ - 10$^{-3}$, revealing the existence of two distinct broad regions: an excess distributed around 40$^{\circ}$ to 90$^{\circ}$ in Right Ascension (commonly referred to as "tail.in" excess) and a deficit (the "loss cone") around 150$^{\circ}$ to 240$^{\circ}$ in Right Ascension. In recent years the Milagro and ARGO-YBJ collaborations reported the of a "medium" scale anisotropy inside the tail-in region. The observation of such small features has been recently claimed by the IceCube experiment also in the Southern hemisphere. So far, no theory of cosmic rays in the Galaxy exists which is able to explain the origin of these different anisotropies leaving the standard model of cosmic rays and that of the galactic magnetic field unchanged at the same time.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑