共查询到19条相似文献，搜索用时 125 毫秒
1.
高能宇宙线的起源、加速和传播是重大的前沿科学问题,回答该问题需要对宇宙线的能谱、各向异性以及各类高能天体电磁辐射进行精确观测.通过空间粒子探测器对宇宙线各成分能谱的直接测量是研究宇宙线物理问题的重要手段.中国于2015年底发射并持续运行至今的暗物质粒子探测卫星以其大接受度、高能量分辨率等特点,在宇宙线直接探测方面取得了系列重要成果,揭示出质子、氦核、硼碳和硼氧比例等宇宙线能谱的新结构,为理解宇宙线起源等科学问题提供了新的依据.介绍了暗物质粒子探测卫星的仪器设置、运行状况、科学成果及其物理意义. 相似文献
2.
宇宙线发现百年以来,宇宙线起源仍然是一个谜.研究宇宙线起源主要在甚高能(VHE)伽马射线天文学和宇宙线物理学两个领域交叉展开.新一代高海拔宇宙线观测站(LHAASO)拥有高海拔、全天候和大规模优势,利用多种探测手段对宇宙线开展联合观测,大幅提升对伽马射线和宇宙线的鉴别能力. LHAASO将开展全天区伽马源扫描搜索以大量发现新伽马源,将获得30 TeV以上伽马射线探测的最高灵敏度,将在宽达5个数量级的能量范围内精确测量宇宙线分成份能谱,为揭开宇宙线起源谜团给出重要判据.系统介绍了LHAASO的探测器结构、性能优势和科学目标. 相似文献
3.
伽马射线作为宇宙中极端事件的独特探针,探测伽马射线是人们了解宇宙构成、星体演化和宇宙线起源等的重要途经.伽马天文涉及了宇宙中的各种前沿科学问题并且观测所需能谱跨度极宽(102 keV–102 TeV),针对不同的科学目标和细分谱段,必须利用不同的伽马望远镜探测技术.总结了空间和地面的共5大类伽马射线观测技术,分别是编码孔径望远镜、康普顿望远镜、电子对望远镜、成像大气切伦科夫望远镜和广延大气簇射阵列;回顾了70 yr来在观测设备和技术进步的推动下伽马射线天文学领域的巨大进展,其中包含高能和甚高能谱段取得的大量成就,中低能段由于已有观测任务有限以及灵敏度低,超高能和极高能段由于观测难度大、起步时间晚,数据和成果相对其他谱段产出较少;展望了未来已经规划的伽马望远镜任务、能力及预期科学产出,其中,中低能段空间望远镜增强型ASTROGAM望远镜(e-ASTROGAM)、全天区中能伽马射线观测站(AMEGO)和甚高能段地面望远镜阵列高海拔宇宙线观测站(LHAASO)、切伦科夫望远镜阵列(CTA),由于灵敏度较同谱段已有任务灵敏度有大幅提升,极有可能在20 yr内从不同角度再度扩展人类对伽马宇宙的认知. 相似文献
4.
宇宙线的起源是高能天体物理的核心问题之一.一直以来,超新星爆发被认为是能谱膝区以下宇宙线的主要来源.多波段观测表明,超新星遗迹有能力加速带电粒子至亚PeV (10~(15)eV)能量.扩散激波加速被认为是最有效的天体高能粒子加速机制之一,而超新星遗迹的大尺度激波正好为这一机制提供平台.近年来,一系列较高精度的地面和空间实验极大地推动了对宇宙线以及超新星遗迹的研究.新的观测事实挑战着传统的扩散激波加速模型以及其在银河系宇宙线超新星遗迹起源学说上的应用,深化了人们对宇宙高能现象的认识.结合超新星遗迹辐射能谱的时间演化特性,构建的时间依赖的超新星遗迹粒子加速模型,不仅能够解释200 GV附近宇宙线的能谱反常,还自然地形成能谱膝区,甚至可以将超新星遗迹粒子加速对宇宙线能谱的贡献延伸至踝区.该模型预期超新星遗迹中粒子的输运行为表现为湍流扩散,这需要未来的观测以及与粒子输运相关的等离子体数值模拟工作来进一步验证. 相似文献
5.
《天文学进展》2021,(1)
银河系外的伽马射线辐射源主要是耀变体,对其研究有助于揭示活动星系核喷流物理、高能宇宙线起源甚至宇宙演化等。研究了为什么有些蝎虎天体有强的伽马射线辐射,而有些却没有。选了170个有多普勒因子和能谱曲率测量的蝎虎天体,并把它们分成被费米LAT探测到的和未被费米LAT探测到的两类。研究发现这两类源的多波段能谱曲率有显著区别,即费米LAT探测到的源的曲率明显小于未被费米LAT探测到的源;即使扣除了多普勒因子的影响,结果也相近。蝎虎天体PKS 0048-09和S5 0716+714有着相似的同步辐射光度但却不同的伽马射线光度。基于同步自康普顿模型,再结合二次曲线电子谱可以很好地拟合它们的多波段能谱,并发现拟合的曲率和辐射区尺度不同但却成正比。PKS 0048-09可能有一个更致密的喷流,从而产生了更大康普顿因子。结果表明,给定同步辐射光度,能谱曲率和康普顿因子对于能否被Fermi伽马射线卫星探测到非常重要;讨论了这一结果对粒子统计加速和辐射机制的限制。 相似文献
6.
暗物质空间探测器BGO量能器的读出设计 总被引：2，自引：0，他引：2
暗物质空间探测器是中国科学院紫金山天文台暗物质空间天文实验室提出的,其目的是为了探测暗物质粒子湮灭可能产生的高能电子和伽玛粒子.整个探测器主要由BGO(Bismuth germanate,锗酸铋)高能图像量能器和闪烁体径迹探测器构成.探测器的能量探测范围将覆盖10 GeV到10 TeV的高能电子和伽玛粒子,其中高能粒子的能量主要沉积在BGO量能器中.为了验证探测器方案,紫金山天文台暗物质空间天文实验室设计了暗物质空间探测器BGO量能器的读出系统原型,并对其进行了初步的测试. 相似文献
7.
极高能宇宙线是能量高于≈10^19 eV的带电或中性的宇宙线粒子。其成分和形成机制的研究是宇宙线物理的重要内容之一，对高能天体物理、粒子物理和宇宙学等相关学科具有重要意义，而且很可能是揭示某些新的基本物理规律的突破点。围绕GZK疑难，重点综述了极高能宇宙线的观测和理论研究现状，对其研究前景作了展望。 相似文献
8.
暗物质粒子探测卫星(Dark Matter Particle Explorer,DAMPE)是一个空间高能宇宙射线探测器.DAMPE的有效载荷包括塑闪阵列探测器、硅阵列探测器、BGO(Bismuth germanate)量能器、中子探测器(Neutron Detector,NUD)以及载荷数管5个分系统,这5个分系统协同完成宇宙线事例信息的采集.卫星发射之前需要对有效载荷的功能进行系统性验证,因此基于Lab Windows/CVI(C programming language Virtual Instrument)开发平台建设了一套用于暗物质粒子探测卫星有效载荷系统测试的地面综合测试系统.该系统实现了有效载荷系统测试的集成化、自动化,提高了测试的安全性、可靠性和测试效率,为暗物质粒子探测卫星有效载荷的顺利交付提供了保障. 相似文献
9.
暗物质空间探测器是中国科学院紫金山天文台空间实验室提出的,其目的是为了探测暗物质粒子湮灭可能产生的高能电子和伽玛粒子.BGO量能器是暗物质粒子探测卫星主要载荷之一,高能粒子的能量主要沉积在BGO量能器中.为了使探测器覆盖5 GeV~10T'eV的探测范围,要求每个BGO探测单元具有约1.5×10~5的动态范围.为了对这一大动态范围的探测单元进行测试,提出一种比较简易的线性测试方法,并在实验室构建一个相应的测试系统,对BGO量能器探测单元读出系统的线性进行测试.测试结果表明BGO量能器探测单元读出的非线性度好于2.7%. 相似文献
10.
本文根据卫星提供的1963—1978年太阳风实验资料,将太阳风中的质子流作为极低能宇宙线,则能得到0.3—4kev的质子积分通量—动能曲线,使低能宇宙线的能谱向前推进了约三个数量级。所得的极低能宇宙线能谱亦呈幂律谱,即:J(>E)=A_sE~(-γ),具有双幂指数,约在1kev处发生转折,与低能太阳宇宙线能谱非常类似。 最近,卫星ISEE—3观测到46次与行星际激波相联系的高能暴粒子(ESP)事例,在能域35—53kev的各次质子峰值强度恰好绘于联结两能谱的虚线之中。这样,从太阳风、ESP、太阳高能粒子(SEP)到太阳低能宇宙线的能谱都被连接了起来,对于它们的起源,也能获得合理地很好地解释。 相似文献
11.
《Chinese Astronomy and Astrophysics》2020,44(1):1-31
The origin of cosmic rays is one of the key questions in high-energy astrophysics. Supernovae have been always considered as the dominant sources of cosmic rays below the energy spectrum knee. Multi-wavelength observations indeed show that supernova remnants are capable for accelerating particles into sub-PeV (10 eV) energies. Diffusive shock acceleration is considered as one of the most efficient acceleration mechanisms of astrophysical high-energy particles, which may just operate effectively in the large-scale shocks of supernova remnants. Recently, a series of high-precision ground and space experiments have greatly promoted the study of cosmic rays and supernova remnants. New observational features challenge the classical acceleration model by diffusive shock and the application to the scenario of supernova remnants for the origin of Galactic cosmic rays, and have deepened our understanding to the cosmic high-energy phenomena. In combination with the time evolution of radiation energy spectrum of supernova remnants, a time-dependent particle acceleration model is established, which can not only explain the anomalies in cosmic-ray distributions around 200 GV, but also naturally form the cosmic-ray spectrum knee, even extend the contribution of supernova particle acceleration to cosmic ray flux up to the spectrum ankle. This model predicts that the high-energy particle transport behavior is dominated by the turbulent convection, which needs to be verified by future observations and plasma numerical simulations relevant to the particle transport. 相似文献
12.
An analysis has been made of the fraction of ultra high energy cosmic rays (above 1018 eV) which could be due to processes involved in two possible ‘Models’. The first is the Giant Magnetic Halo Model and the second is the Dark Matter Halo Model. We find that the former, in which heavy nuclei are trapped in a giant halo, fails for energies above about 3 × 1019 eV. For the Dark Matter Halo Model, in which relic particles follow the “conventional” dark matter and whose decays give ultra high energy cosmic rays, the predicted anisotropies are much higher than those observed. The lack of observation of a finite flux from the Andromeda Galaxy means that the conclusion is insensitive to the spatial scale size of the assumed halo distribution. It is concluded that less than 10% of the ultra high energy cosmic rays come from relic particles in the Galactic halo. 相似文献
13.
The history of cosmic ray studies can be traced back to the 1910s when Hess and other scientists first discovered them. Cosmic rays are very important laboratories of particle physics, and have led to many important discoveries of fundamental particles, such as the positrons, muons, pions, and a series of strange particles. Cosmic rays are nowadays the key probes of the extremely high-energy physics and dark matter particles. A brief review about the history and recent progresses of direct observations of cosmic rays is presented. In recent years, the new space-borne experiments such as PAMELA and AMS-02, as well as a few of balloon-borne experiments, have measured the energy spectra of cosmic rays very precisely, and revealed several new features/anomalies. Remarkable excesses of positron fraction in the total electron plus positron fluxes have been observed, which may be caused by the annihilation/decay of dark matter particles or by astrophysical pulsars. The cosmic ray antiprotons, which are expected to have the same secondary origin as that of positrons, do not show significant excesses compared with the background prediction. This result also constrains the modeling of the positron excesses. In addition, the spectral hardening above several hundred GeV of cosmic ray nuclei has been revealed. These results have important and interesting implications on our understandings of the origin, acceleration, and propagation of cosmic rays. In particular, China has launched the Dark Matter Particle Explorer (DAMPE) to indirectly search for the dark matter and explore the high-energy universe in the TeV window. Most recently, the DAMPE collaborators reported the new measurements of the cosmic ray electron plus positron fluxes up to about 5 TeV with a very high precision. The DAMPE data revealed clearly a deflection around 0.9 TeV in the electron energy spectrum. Possible fine structures of the electron plus positron spectra can be critically addressed with the accumulation of data in the coming years. 相似文献
14.
Marcin Jankiewicz Roman V. Buniy Thomas W. Kephart Thomas J. Weiler 《Astroparticle Physics》2004,21(6):651-666
It has been proposed that propagation of cosmic-rays at extreme-energy may be sensitive to Lorentz-violating metric fluctuations (“foam”). We investigate the changes in interaction thresholds for cosmic-rays and gamma-rays interacting on the CMB and IR backgrounds, for a class of stochastic models of space–time foam. The strength of the foam is characterized by the factor (E/MP)a, where a is a phenomenological suppression parameter. We find that there exists a critical value of a (dependent on the particular reaction: acrit3 for cosmic-rays, 1 for gamma-rays), below which the threshold energy can only be lowered, and above which the threshold energy may be raised, but at most by a factor of two. Thus, it does not appear possible in this class of models to extend cosmic-ray spectra significantly beyond their classical absorption energies. However, the lower thresholds resulting from foam may have signatures in the cosmic-ray spectrum. In the context of this foam model, we find that cosmic-ray energies cannot exceed the fundamental Planck scale, and so set a lower bound of 108 TeV for the scale of gravity. We also find that suppression of p→pπ0 and γ→e−e+ “decays” favors values aacrit. Finally, we comment on the apparent non-conservation of particle energy–momentum, and speculate on its re-emergence as dark energy in the foamy vacuum. 相似文献
15.
We study the impact of possible spiral-arm distributions of Galactic cosmic-ray sources on the flux of various cosmic-ray nuclei throughout our Galaxy. We investigate model cosmic-ray spectra at the nominal position of the sun and at different positions within the Galaxy. The modelling is performed using the recently introduced numerical cosmic ray propagation code Picard. Assuming non-axisymmetric cosmic-ray source distributions yields new insights on the behaviour of primary versus secondary nuclei.We find that primary cosmic rays are more strongly confined to the vicinity of the sources, while the distribution of secondary cosmic rays is much more homogeneous compared to the primaries. This leads to stronger spatial variation in secondary to primary ratios when compared to axisymmetric source distribution models. A good fit to the cosmic-ray data at Earth can be accomplished in different spiral-arm models, although leading to decisively different spatial distributions of the cosmic-ray flux. These lead to different cosmic ray anisotropies, where even reproducing the data becomes possible. Consequently, we advocate directions to seek best fit propagation parameters that take into account the higher complexity introduced by the spiral-arm structure on the cosmic-ray distribution. We specifically investigate whether the flux at Earth is representative for a large fraction of the Galaxy. The variance among possible spiral-arm models allows us to quantify the spatial variation of the cosmic-ray flux within the Galaxy in presence of non-axisymmetric source distributions. 相似文献
17.
We study the individual contribution to secondary lepton production in hadronic interactions of cosmic rays (CRs) including resonances and heavier secondaries. For this purpose we use the same methodology discussed earlier [C.-Y. Huang, S.-E. Park, M. Pohl, C.D. Daniels, Astropart. Phys. 27 (2007) 429], namely the Monte-Carlo particle collision code DPMJET3.04 to determine the multiplicity spectra of various secondary particles with leptons as the final decay states, that result from inelastic collisions of cosmic-ray protons and Helium nuclei with the interstellar medium of standard composition. By combining the simulation results with parametric models for secondary particle (with resonances included) for incident cosmic-ray energies below a few GeV, where DPMJET appears unreliable, we thus derive production matrices for all stable secondary particles in cosmic-ray interactions with energies up to about 10 PeV.
We apply the production matrices to calculate the radio synchrotron radiation of secondary electrons in a young shell-type SNR, RX J1713.7-3946, which is a measure of the age, the spectral index of hadronic cosmic rays, and most importantly the magnetic field strength. We find that the multi-mG fields recently invoked to explain the X-ray flux variations are unlikely to extend over a large fraction of the radio-emitting region, otherwise the spectrum of hadronic cosmic rays in the energy window 0.1–100 GeV must be unusually hard.
We also use the production matrices to calculate the muon event rate in an IceCube-like detector that are induced by muon neutrinos from high-energy γ-ray sources such as RX J1713.7-3946, Vela Jr. and MGRO J2019+37. At muon energies of a few TeV, or in other word, about 10 TeV neutrino energy, an accumulation of data over about 5–10 years would allow testing the hadronic origin of TeV γ-rays. 相似文献
18.
K. Bernlöhr W. Hofmann G. Leffers V. Matheis M. Panter R. Zink 《Astroparticle Physics》1998,8(4):253-264
Data taken with ten Cosmic Ray Tracking (CRT) detectors and the HEGRA air-shower array on La Palma, Canary Islands, have been analysed to investigate changes of the cosmic
ay mass composition at the ‘knee’ of the cosmic-ray flux spectrum near 1015 eV energy. The analysis is based on the angular distributions of particles in air showers. HEGRA data provided the shower size, direction, and core position and CRT data the particle track information. It is shown that the angular distribution of muons in air showers is sensitive to the composition over a wide range of shower sizes and, thus, primary cosmic-ray energies with little systematic uncertainties. Results can be easily expressed in terms of ln A of primary cosmic rays. In the lower part of the energy range covered, we have considerable overlap with direct composition measurements by the JACEE collaboration and find compatible results in the observed rise of ln A. Above about 1015 eV energy we find no or at most a slow further rise of ln A. Simple cosmic-ray composition models are presented which are fully consistent with our results as well as the JACEE flux and composition measurements and the flux measurements of the Tibet ASγ collaboration. Minimal three-parameter composition models defined by the same power-law slope of all elements below the knee and a common change in slope at a fixed rigidity are inconsistent with these data. 相似文献
19.
Francesco Miniati 《Monthly notices of the Royal Astronomical Society》2002,337(1):199-208
We investigate numerically the contribution to the cosmic gamma-ray background from cosmic-ray ions and electrons accelerated at intergalactic shocks associated with cosmological structure formation. We show that the kinetic energy of accretion flows in the low-redshift intergalactic medium is thermalized primarily through moderately strong shocks, which allow for an efficient conversion of shock ram pressure into cosmic-ray pressure. Cosmic rays accelerated at these shocks produce a diffuse gamma-ray flux which is dominated by inverse Compton emission from electrons scattering off cosmic microwave background photons. Decay of neutral π mesons generated in p–p inelastic collisions of the ionic cosmic-ray component with the thermal gas contribute about 30 per cent of the computed emission. Based on experimental upper limits on the photon flux above 100 MeV from nearby clusters we constrain the efficiency of conversion of shock ram pressure into relativistic CR electrons to ≲1 per cent . Thus, we find that cosmic rays of cosmological origin can generate an overall significant fraction of order 20 per cent and no more than 30 per cent of the measured gamma-ray background. 相似文献