对宇宙线能谱变硬现象的研究  

Studying the High-energy Hardening Observed in Cosmic Ray Spectra

作　　者：龙韦成 胡皓然 吴娟[1] LONG Wei-cheng;HU Hao-ran;WU Juan(School of Mathematics and Physics,China University of Geosciences,Wuhan 430074)

机构地区：[1]中国地质大学数学与物理学院,武汉430074

出　　处：《天文学报》2024年第5期37-47,共11页Acta Astronomica Sinica

基　　金：国家自然科学基金项目(U1738130)资助。

摘　　要：近年来,随着宇宙线探测技术的不断提高,各空间探测实验对宇宙线粒子进行了高精度测量.其中,在宇宙线原初粒子和次级粒子能谱中,均发现在几百GV处存在能谱变硬特征.特别是,阿尔法磁谱仪2(Alpha Magnetic Spectrometer 2,AMS-2)实验发现次级粒子相较原初粒子能谱变硬程度更为显著.目前,导致这一现象的原因还尚未有定论.论文利用AMS-2、反物质探测和轻核天体物理载荷(Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics,PAMELA)、先进成分探测器(Advanced Composition Explorer,ACE)中的宇宙线同位素光谱仪(Cosmic Ray Isotope Spectrometer,CRIS)(ACE-CRIS)以及旅行者1号(Voyager-1)探测器的最新实验数据对这一问题进行了研究.数据包括质子(p)和碳核(C)两种类型的原初粒子能谱以及锂碳比(Li/C)、铍碳比(Be/C)和硼碳比(B/C)3种类型的次级粒子原初粒子能谱比.论文分别假定高能区变硬现象是由发射谱拐折或是扩散拐折两种不同因素所导致,在此基础上对扩散-重加速(diffusionreacceleration,DR)以及扩散-对流(diffusion-convection,DC)两种不同的模型框架进行分析.在各模型框架下,计算结果显示:在低-中能区,各模型扩散指数δ_(L)的最佳估算值在0.41-0.48之间.其中,DR模型所需的δ_(L)值要比DC模型低0.06左右,这说明相较于对流,重加速机制会导致(Li,Be,B)/C在1至几百GeV/n之间的形状变陡.因此,拟合同样的(Li,Be,B)/C数据,DR模型所需的扩散指数更小.在高能区,结合暗物质探测卫星实验(the Dark Matter Particle Explorer,DAMPE)测量的B/C数据,我们发现相较于注入谱的高能拐折效应,DAMPE观测到的B/C高能区硬化现象更倾向于用扩散指数的变化来解释.不管是DR还是DC模型,得到的扩散指数拐折参数△δ都约为-0.19.In recent years,with the continuous improvement of cosmic ray detection technology,various space experiments have carried out high precision measurements on cosmic ray particles.A hardening at several hundred GV in cosmic rays spectra has been exhibited for both the primary and secondary cosmic ray fluxes.Especially,the Alpha Magnetic Spectrometer 2(AMS-2)experiment found that secondary particles harden more significantly than primary particles.At present,the reason for this hardening remains uncertain.In this work,we employ the data measured by AMS-2,Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics(PAMELA),the Cosmic Ray Isotope Spectrometer on the Advanced Composition Explorer(ACE-CRIS)and the spacecraft Voyager-1 to investigate this question.The data contain two types of primary spectra including proton(p)and carbon nuclei(C),and three types of secondary-to-primary ratios including the lithium-to-carbon ratio(Li/C),the beryllium-to-carbon ratio(Be/C)and the boron-to-carbon ratio(B/C).This work assumes the high-energy hardening phenomenon is caused either by a high-energy break in the injection spectra,or by a high-energy break in the diffusion coefficient.Based on this assumption,two different frameworks are analysed,including the diffusionreacceleration(DR)configuration and the diffusion-convection(DC)configuration.Under each framework,the estimated value of diffusion slopeδ_(L) is found between 0.41 and 0.48 in the low-to-intermediate energy range.The value ofδ_(L) required by the DR model is about 0.06 lower than that in the DC model.It indicates that,compared with the convection process,the reacceleration mechanism will cause the shape of(Li,Be,B)/C to become steeper from GeV/n to hundreds of GeV/n.Therefore,by fitting to the same(Li,Be,B)/C data,the DR model requires a smaller diffusion slope.In the high energy region,combined with recent B/C data measured by Dark Matter Particle Explorer(DAMPE),it is found that the highenergy hardening feature observed in DAMPE B/C ratio is more

关 键 词：星际介质:宇宙线 扩散 对流 湍流 

分 类 号：P172[天文地球—天文学]