利用羊八井ASγ Ⅲ期阵列研究宇宙线各向异性随时间的演化
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摘要
地球一直处在高能粒子的轰击中,这些粒子就是宇宙射线,它们(主要成分为质子)从宇宙深处而来。虽然自宇宙线的发现以来已经过了近百年,但这些高能粒子的起源以及如何加速到如此高的能量,到现在仍未能完全解答。大多数的宇宙线被认为是起源于我们银河系内的,由超新星遗迹(SNRs)所加速,它们从遥远的地方穿过星际空间及日球层最终到达地球,我们观测到的宇宙线由于在传播过程中受到了银河系磁场的偏转而整体显出各向同性的性质。但是,有众多的实验发现,在整体各向同性的背景上,宇宙线强度存在着轻微但明显的各向异性。这种各向异性带有宇宙线起源、加速及传播过程中的信息,因此对各向异性的研究在宇宙线物理中具有重要的意义。
直到现在,对各向异性的成因仍未有一致的被广泛认可的解释。宇宙线的各向异性有以下几个可能的起因:首先,它可能是由加速源的不均匀分布以及宇宙线在银河系空间中的传播过程有关。其次,大尺度以及局部的磁场结构也会引起宇宙线的各向异性,这其中可能包括日球层的效应。另外,由观测者和宇宙线等离子体之间的相对运动也可产生各向异性,这种效应被称为“Compton-Getting”效应。
从多家实验的分析来看,在几十GeV到PeV这个很宽的能量范围内,宇宙线各向异性的一阶谐波振幅和相位都是随能量而变化的。在几十GeV之下,太阳活动对宇宙线有很强的调制作用,宇宙线进入日球层后与太阳风磁场相互作用,因此该能量宇宙线的各向异性可以反映太阳风磁场的结构。随能量增高,宇宙线对太阳调制愈加不敏感。在multi-TeV能量,宇宙线粒子达几百AU的回旋半径已和日球层空间的尺度相当,但是众所周知,日球层有一条长长的尾巴,这条长尾对于该能量的宇宙线依然可能存在调制效应。因此这个能量的大尺度各向异性可以给出关于日球层磁场结构或日球附近星际空间局域结构的重要信息。
太阳有着约11年的活动周期,且它的磁场极性有着跨越两个太阳周期的长周期。既然multi-TeV宇宙线有可能受到太阳活动的调制,也就可以预期各向异性会随太阳周期而变化。有许多实验都研究了宇宙线各向异性同太阳活动的关联,但它们得出的结论却有相互冲突的地方,这需要更多的实验观测以作研究。与此同时,实验发现600 GV刚度的宇宙线太阳时各向异性有随太阳活动相关的周期11年的变化,这或许可以给出太阳活动对太阳时各向异性影响的能量上限。Tibet ASγ实验也报道了在4 TeV处超出预期CG效应的太阳时各向异性调制,这显示太阳活动对太阳时各向异性的调制或许可以延伸至multi-TeV能量。本工作中对于该能量宇宙线太阳时各向异性随太阳活动的时间演化关系可以给出有关这种额外效应的理解。
Tibet ASγEAS阵列实验位于中国西藏羊八井镇(90.522°E,30.102°N,海拔4300米),于1990年建成。1999年秋,TibetⅢ阵列配置完成。由于具有大视场、高探测事例率以及良好的角分辨能力,TibetⅢ阵列可以得出目前国际上最精细的multi-TeV能量宇宙线强度的测量。利用等天顶角原理,一种发展成熟的分析方法可以给出宇宙线强度的两维结构。相比较先前实验所只能给出的简单的宇宙线随时间的一维分布,这种两维结构可以给出更多细致的信息以帮助我们认识和理解各向异性。TibetⅢ的运行观测期为1999.11—2008.12,这包含了第23个太阳周期太阳活动由极大到极小整个后半部分的时期。因此,我们能够给出更多关于宇宙线各向异性随太阳活动时间变化的信息,不止是先前实验所做的单纯的一维分布的谐波参数的变化,还包括两维分布天图随时间在不同年份的性质。
由于存在不同周期的各向异性调制,因此在分析每个单独周期的各向异性时,需要有足够长时期的观测以消除不同周期各向异性之间的相互干扰。另外考虑到由探测器的死时间而产生的不均匀的事例率,我们需要对观测数据作活时间修正。要去研究短期内的各向异性,之前的方法是难以消除不同周期的相互干扰的,我们需要寻求新的有效方法来消除这些干扰效应。利用Lomb-Scargle Fourier变换方法对TibetⅢ数据的研究结果发现,对于能量在3.0-12 TeV之间的宇宙线,除了我们所知的量级为10~(-3)的各向异性的太阳日、恒星日以及半恒星日周期调制外,在一小时到两年的范围内,没有探测到其它周期的各向异性调制。基于这个结论,在本工作中,认为在某一时刻某一方向(对地平坐标系而言)上的宇宙线强度是由太阳时周期和恒星时周期下对应的相应位置上两个各向异性的独立效应的合效应,这并不受事例数分布不均的影响。同ASγ实验之前的分析方法不同,对于相对较短时期观测来说,本工作可以同时得到太阳时和恒星时下的宇宙线各向异性,且无需作因事例分布不均所要求的活时间修正。
在本文中,利用TibetⅢ运行期的数据,我们分析了multi-TeV宇宙线太阳时各向异性和恒星时各向异性年与年之间随时间的变化。除了一维谐波拟合参数的时间演化,我们还看到了各向异性两维分布在不同年份的结构特征随时间的演化。我们发现,在TibetⅢ整个观测时期里,太阳时各向异性和恒星时各向异性都是比较稳定的。注意到,由于缺乏太阳极性反转前足够的统计量,我们无法研究太阳极性的反转对各向异性结构稳定性的影响。要研究这种效应,需要我们持续现在ASγ实验对宇宙线各向异性的观测。对于各向异性的本质及其它一些尚未解决的问题,也需要我们进一步的研究和努力。
概括来说,本论文工作主要有以下三个创新点:第一,用本论文所引入的研究方法,我们利用短期观测的少量数据同时拟合得出太阳时周期和恒星时周期下的宇宙线各向异性,且避免了之前方法所必需要做的活时间修正步骤。第二,我们给出了准确合理的由两维天图到一维分布的投影方法,并作相应的谐波函数拟合,以此便于与之前实验的谐波分析结果相比较。且这种方法经过了Monte Carlo的检验。第三,我们得到了multi-TeV宇宙线在太阳时和恒星时周期下的各向异性随时间演化性质的最高精度的观测结果,这不仅包含与其它实验相同的一维谐波拟合参数随时间的变化,更给出了空间两维结构随时间的演化特征。本论文的不足之处在于:由于缺乏最近太阳极性反转前足够的统计量,我们无法得出太阳极性反转对于各向异性结构变化的影响。若进一步研究该效应,需要我们进行持续稳定的观测。
The Earth is continuously bombarded by highly energetic particles-the cosmic rays(CRs).CRs are high-energy nuclei(mostly protons) from outer space.For nearly 100 years after their discovery,the origin and acceleration of the highest energy particles are still unknown.Most CRs are believed to be accelerated by supernova remnants (SNRs) in our Galaxy and continuously reach the Earth after propagating through the Galaxy and heliosphere.The intensity of CRs is nearly isotropic due to deflections of CRs in the Galactic magnetic field(GMF).However,extensive observations do show that there exists a slight anisotropy on the overall isotropic background.The research of CR anisotropy plays an important role because it has close relationship with the origin,acceleration and propagation of CRs.
Until now,there are no convincing and widely accepted explanations for CR anisotropy.It may arise from several causes as follows.Firstly,it may result from the uneven distribution of CR sources such as SNRs and the process of CR propagation in the Galaxy.Secondly,the anisotropy can also be induced through both large-scale and local magnetic field configurations,possibly including effects of the heliosphere.In addition,an expected anisotropy is caused by the relative motion between the observer and the CR plasma,known as the Compton-Getting(CG) effect.
From the analysis of numerous experiments,it can be seen that both the amplitude and the phase of the best-fit first harmonic vary with CR energy in a wide range from tens of GeV to PeV.Below several tens of GeV,solar modulation effects are most notable for CRs.CRs interact with the solar wind magnetic field,both an regular field and irregular field components,after entering the heliosphere.The spatial distribution of CRs can reflect the magnetic structure in the solar wind.With increasing energy, CRs become less sensitive to the solar modulation.In the multi-TeV range,the gyro radius of hundreds of AU becomes comparable to the spatial scale of the heliosphere in the nose direction toward the upstream of the interstellar medium flow.However,it is known that the heliosphere has a long heliotail,the modulation in the heliotail remains possible.Therefore,the large-scale sidereal anisotropy of CRs in this energy range gives us an important clue about the magnetic field structure of the heliosphere or the local interstellar space surrounding the heliosphere.
The solar cycle shows a quasi-period of about 11 years and the global magnetic polarity reverses with a quasi-period of two solar activity cycles.Since CRs may be modulated by solar activities in the multi-TeV range as mentioned above,it might be expected that the sidereal anisotropy may follow the variation of solar cycle.Many experiments have been devoted to study the correlation between CR anisotropy and solar activity.There are contradictions among different observations and needs cross check from other experiments.Meanwhile,the solar anisotropy at 600 GV shows a clear 11-yr change related to the solar activity.It may give the the upper limiting energy of solar modulation in the heliosphere.The Tibet AS_γexperiment also reported the extra modulation which exceeds the expected CG effect at 4 TeV,suggesting the solar modulation effect possibly extending up to multi-TeV energies.In this thesis,the study on the temporal variation of the solar anisotropy at this energy can give useful information to understand the extra effect.
The Tibet AS_γexperiment has been operating successfully at Yangbajing(90.522°E,30.102°N;4300 m above the sea level) in Tibet,China since 1990.The TibetⅢarray was completed in the late fall of 1999.Taking advantage of the large field of view and high count rates as well as the good angular resolution of the incident direction, the TibetⅢAir Shower Array provides currently the world's highest precision measurement of CR intensity in multi-TeV energy range.Using the equi-zenith principle, a developed analysis method can give two-dimensional structures of CR intensity. This analysis gives more information than simple 1D analysis in understanding the anisotropy.The observation period runs from 1999 November to 2008 December, covering more than a half of the 23rd solar activity cycle from the maximum to the minimum.Therefore,we can do more precise study on the anisotropy year by year in correlation with the solar cycle,not only the simple 1D profile as given by former experiments,but also the variations of 2D CR intensity maps in correlation with the solar activity.
With previously developed method,when we analyze the anisotropy in each different period,the data have to be taken for a long enough time to avoid the mutual interference of the adjacent periods.We also have to do live time correction,considering the uneven event rate due to the discontinuous observational data taking.To study the CR anisotropy in a short term interval,we should look for a new effective method to avoid the mutual interference of different period.Using Lomb-Scargle Fourier transformation method with CR data recorded by the TibetⅢarray,Tibet AS_γexperiment has showed that except the well-known solar diurnal,sidereal diurnal and sidereal semi-diurnal modulations at a level of～10~(-3),no other periodicity was found to have high enough significance from 1 hour to 2 years in the energy range from～3.0 TeV to～12.0 TeV.Based on this,we assume that at any moment t,the relative intensity of multi-TeV CRs at any given direction is modulated as a product of intensities in two different periods respectively.Different from the former method used in AS_γ, we can obtained the CR intensity variations both in the sidereal time and the solar time simultaneously using the relative short-time observations,and need not to do the live time correction due to the uneven observational data taking.
In this thesis,we analyze temporal variations of solar anisotropy and sidereal anisotropy of multi-TeV CR intensity using the data of TibetⅢarray from 1999 November to 2008 December.Besides the results of temporal variations of 1D harmonics fit parameters,we gives the variations with time of 2D anisotropy structures. We found that both sidereal and solar anisotropy are stable during entire TibetⅢobservations. Note that at this point,we cannot investigate the influence of the polarity reversal of the global solar magnetic field on the sidereal anisotropy due to the lack of data before the current magnetic field reversal.We do not use the data of Tibet HD to perform the year-by-year analysis due to the limitation of the statistics,although it covers the period before the reversal.To study the influence of solar polarity reversal on anisotropy,we should keep on our continuous observations.The nature of the anisotropy and other unsolved problem need our further study.
There are three innovative points in this thesis.Firstly,we can obtain the CR anisotropy using limited data which are taken from short term run phase of detectors. The method can avoid the mutual interference of the adjacent periods,and need not do live time correction used in former analysis.Secondly,it gives the proper 1D projection from 2D sky map,the obtained harmonic parameters can be compared with other experiments.And the property is verified by the corresponding Monte Carlo simulation.Third,we got the highest precision measurement on temporal variations of multi-TeV CR anisotropies both in solar time and sidereal time.Besides variations of the harmonics fits parameter,we can see the variations of the 2D CR intensity maps. And the deficiency of this work is:Limited to the statistics,we can not investigate the influence of the polarity reversal of the solar magnetic field.It needs our further continuous observations until covering the next reversal of solar polarity.
直到现在,对各向异性的成因仍未有一致的被广泛认可的解释。宇宙线的各向异性有以下几个可能的起因:首先,它可能是由加速源的不均匀分布以及宇宙线在银河系空间中的传播过程有关。其次,大尺度以及局部的磁场结构也会引起宇宙线的各向异性,这其中可能包括日球层的效应。另外,由观测者和宇宙线等离子体之间的相对运动也可产生各向异性,这种效应被称为“Compton-Getting”效应。
从多家实验的分析来看,在几十GeV到PeV这个很宽的能量范围内,宇宙线各向异性的一阶谐波振幅和相位都是随能量而变化的。在几十GeV之下,太阳活动对宇宙线有很强的调制作用,宇宙线进入日球层后与太阳风磁场相互作用,因此该能量宇宙线的各向异性可以反映太阳风磁场的结构。随能量增高,宇宙线对太阳调制愈加不敏感。在multi-TeV能量,宇宙线粒子达几百AU的回旋半径已和日球层空间的尺度相当,但是众所周知,日球层有一条长长的尾巴,这条长尾对于该能量的宇宙线依然可能存在调制效应。因此这个能量的大尺度各向异性可以给出关于日球层磁场结构或日球附近星际空间局域结构的重要信息。
太阳有着约11年的活动周期,且它的磁场极性有着跨越两个太阳周期的长周期。既然multi-TeV宇宙线有可能受到太阳活动的调制,也就可以预期各向异性会随太阳周期而变化。有许多实验都研究了宇宙线各向异性同太阳活动的关联,但它们得出的结论却有相互冲突的地方,这需要更多的实验观测以作研究。与此同时,实验发现600 GV刚度的宇宙线太阳时各向异性有随太阳活动相关的周期11年的变化,这或许可以给出太阳活动对太阳时各向异性影响的能量上限。Tibet ASγ实验也报道了在4 TeV处超出预期CG效应的太阳时各向异性调制,这显示太阳活动对太阳时各向异性的调制或许可以延伸至multi-TeV能量。本工作中对于该能量宇宙线太阳时各向异性随太阳活动的时间演化关系可以给出有关这种额外效应的理解。
Tibet ASγEAS阵列实验位于中国西藏羊八井镇(90.522°E,30.102°N,海拔4300米),于1990年建成。1999年秋,TibetⅢ阵列配置完成。由于具有大视场、高探测事例率以及良好的角分辨能力,TibetⅢ阵列可以得出目前国际上最精细的multi-TeV能量宇宙线强度的测量。利用等天顶角原理,一种发展成熟的分析方法可以给出宇宙线强度的两维结构。相比较先前实验所只能给出的简单的宇宙线随时间的一维分布,这种两维结构可以给出更多细致的信息以帮助我们认识和理解各向异性。TibetⅢ的运行观测期为1999.11—2008.12,这包含了第23个太阳周期太阳活动由极大到极小整个后半部分的时期。因此,我们能够给出更多关于宇宙线各向异性随太阳活动时间变化的信息,不止是先前实验所做的单纯的一维分布的谐波参数的变化,还包括两维分布天图随时间在不同年份的性质。
由于存在不同周期的各向异性调制,因此在分析每个单独周期的各向异性时,需要有足够长时期的观测以消除不同周期各向异性之间的相互干扰。另外考虑到由探测器的死时间而产生的不均匀的事例率,我们需要对观测数据作活时间修正。要去研究短期内的各向异性,之前的方法是难以消除不同周期的相互干扰的,我们需要寻求新的有效方法来消除这些干扰效应。利用Lomb-Scargle Fourier变换方法对TibetⅢ数据的研究结果发现,对于能量在3.0-12 TeV之间的宇宙线,除了我们所知的量级为10~(-3)的各向异性的太阳日、恒星日以及半恒星日周期调制外,在一小时到两年的范围内,没有探测到其它周期的各向异性调制。基于这个结论,在本工作中,认为在某一时刻某一方向(对地平坐标系而言)上的宇宙线强度是由太阳时周期和恒星时周期下对应的相应位置上两个各向异性的独立效应的合效应,这并不受事例数分布不均的影响。同ASγ实验之前的分析方法不同,对于相对较短时期观测来说,本工作可以同时得到太阳时和恒星时下的宇宙线各向异性,且无需作因事例分布不均所要求的活时间修正。
在本文中,利用TibetⅢ运行期的数据,我们分析了multi-TeV宇宙线太阳时各向异性和恒星时各向异性年与年之间随时间的变化。除了一维谐波拟合参数的时间演化,我们还看到了各向异性两维分布在不同年份的结构特征随时间的演化。我们发现,在TibetⅢ整个观测时期里,太阳时各向异性和恒星时各向异性都是比较稳定的。注意到,由于缺乏太阳极性反转前足够的统计量,我们无法研究太阳极性的反转对各向异性结构稳定性的影响。要研究这种效应,需要我们持续现在ASγ实验对宇宙线各向异性的观测。对于各向异性的本质及其它一些尚未解决的问题,也需要我们进一步的研究和努力。
概括来说,本论文工作主要有以下三个创新点:第一,用本论文所引入的研究方法,我们利用短期观测的少量数据同时拟合得出太阳时周期和恒星时周期下的宇宙线各向异性,且避免了之前方法所必需要做的活时间修正步骤。第二,我们给出了准确合理的由两维天图到一维分布的投影方法,并作相应的谐波函数拟合,以此便于与之前实验的谐波分析结果相比较。且这种方法经过了Monte Carlo的检验。第三,我们得到了multi-TeV宇宙线在太阳时和恒星时周期下的各向异性随时间演化性质的最高精度的观测结果,这不仅包含与其它实验相同的一维谐波拟合参数随时间的变化,更给出了空间两维结构随时间的演化特征。本论文的不足之处在于:由于缺乏最近太阳极性反转前足够的统计量,我们无法得出太阳极性反转对于各向异性结构变化的影响。若进一步研究该效应,需要我们进行持续稳定的观测。
The Earth is continuously bombarded by highly energetic particles-the cosmic rays(CRs).CRs are high-energy nuclei(mostly protons) from outer space.For nearly 100 years after their discovery,the origin and acceleration of the highest energy particles are still unknown.Most CRs are believed to be accelerated by supernova remnants (SNRs) in our Galaxy and continuously reach the Earth after propagating through the Galaxy and heliosphere.The intensity of CRs is nearly isotropic due to deflections of CRs in the Galactic magnetic field(GMF).However,extensive observations do show that there exists a slight anisotropy on the overall isotropic background.The research of CR anisotropy plays an important role because it has close relationship with the origin,acceleration and propagation of CRs.
Until now,there are no convincing and widely accepted explanations for CR anisotropy.It may arise from several causes as follows.Firstly,it may result from the uneven distribution of CR sources such as SNRs and the process of CR propagation in the Galaxy.Secondly,the anisotropy can also be induced through both large-scale and local magnetic field configurations,possibly including effects of the heliosphere.In addition,an expected anisotropy is caused by the relative motion between the observer and the CR plasma,known as the Compton-Getting(CG) effect.
From the analysis of numerous experiments,it can be seen that both the amplitude and the phase of the best-fit first harmonic vary with CR energy in a wide range from tens of GeV to PeV.Below several tens of GeV,solar modulation effects are most notable for CRs.CRs interact with the solar wind magnetic field,both an regular field and irregular field components,after entering the heliosphere.The spatial distribution of CRs can reflect the magnetic structure in the solar wind.With increasing energy, CRs become less sensitive to the solar modulation.In the multi-TeV range,the gyro radius of hundreds of AU becomes comparable to the spatial scale of the heliosphere in the nose direction toward the upstream of the interstellar medium flow.However,it is known that the heliosphere has a long heliotail,the modulation in the heliotail remains possible.Therefore,the large-scale sidereal anisotropy of CRs in this energy range gives us an important clue about the magnetic field structure of the heliosphere or the local interstellar space surrounding the heliosphere.
The solar cycle shows a quasi-period of about 11 years and the global magnetic polarity reverses with a quasi-period of two solar activity cycles.Since CRs may be modulated by solar activities in the multi-TeV range as mentioned above,it might be expected that the sidereal anisotropy may follow the variation of solar cycle.Many experiments have been devoted to study the correlation between CR anisotropy and solar activity.There are contradictions among different observations and needs cross check from other experiments.Meanwhile,the solar anisotropy at 600 GV shows a clear 11-yr change related to the solar activity.It may give the the upper limiting energy of solar modulation in the heliosphere.The Tibet AS_γexperiment also reported the extra modulation which exceeds the expected CG effect at 4 TeV,suggesting the solar modulation effect possibly extending up to multi-TeV energies.In this thesis,the study on the temporal variation of the solar anisotropy at this energy can give useful information to understand the extra effect.
The Tibet AS_γexperiment has been operating successfully at Yangbajing(90.522°E,30.102°N;4300 m above the sea level) in Tibet,China since 1990.The TibetⅢarray was completed in the late fall of 1999.Taking advantage of the large field of view and high count rates as well as the good angular resolution of the incident direction, the TibetⅢAir Shower Array provides currently the world's highest precision measurement of CR intensity in multi-TeV energy range.Using the equi-zenith principle, a developed analysis method can give two-dimensional structures of CR intensity. This analysis gives more information than simple 1D analysis in understanding the anisotropy.The observation period runs from 1999 November to 2008 December, covering more than a half of the 23rd solar activity cycle from the maximum to the minimum.Therefore,we can do more precise study on the anisotropy year by year in correlation with the solar cycle,not only the simple 1D profile as given by former experiments,but also the variations of 2D CR intensity maps in correlation with the solar activity.
With previously developed method,when we analyze the anisotropy in each different period,the data have to be taken for a long enough time to avoid the mutual interference of the adjacent periods.We also have to do live time correction,considering the uneven event rate due to the discontinuous observational data taking.To study the CR anisotropy in a short term interval,we should look for a new effective method to avoid the mutual interference of different period.Using Lomb-Scargle Fourier transformation method with CR data recorded by the TibetⅢarray,Tibet AS_γexperiment has showed that except the well-known solar diurnal,sidereal diurnal and sidereal semi-diurnal modulations at a level of～10~(-3),no other periodicity was found to have high enough significance from 1 hour to 2 years in the energy range from～3.0 TeV to～12.0 TeV.Based on this,we assume that at any moment t,the relative intensity of multi-TeV CRs at any given direction is modulated as a product of intensities in two different periods respectively.Different from the former method used in AS_γ, we can obtained the CR intensity variations both in the sidereal time and the solar time simultaneously using the relative short-time observations,and need not to do the live time correction due to the uneven observational data taking.
In this thesis,we analyze temporal variations of solar anisotropy and sidereal anisotropy of multi-TeV CR intensity using the data of TibetⅢarray from 1999 November to 2008 December.Besides the results of temporal variations of 1D harmonics fit parameters,we gives the variations with time of 2D anisotropy structures. We found that both sidereal and solar anisotropy are stable during entire TibetⅢobservations. Note that at this point,we cannot investigate the influence of the polarity reversal of the global solar magnetic field on the sidereal anisotropy due to the lack of data before the current magnetic field reversal.We do not use the data of Tibet HD to perform the year-by-year analysis due to the limitation of the statistics,although it covers the period before the reversal.To study the influence of solar polarity reversal on anisotropy,we should keep on our continuous observations.The nature of the anisotropy and other unsolved problem need our further study.
There are three innovative points in this thesis.Firstly,we can obtain the CR anisotropy using limited data which are taken from short term run phase of detectors. The method can avoid the mutual interference of the adjacent periods,and need not do live time correction used in former analysis.Secondly,it gives the proper 1D projection from 2D sky map,the obtained harmonic parameters can be compared with other experiments.And the property is verified by the corresponding Monte Carlo simulation.Third,we got the highest precision measurement on temporal variations of multi-TeV CR anisotropies both in solar time and sidereal time.Besides variations of the harmonics fits parameter,we can see the variations of the 2D CR intensity maps. And the deficiency of this work is:Limited to the statistics,we can not investigate the influence of the polarity reversal of the solar magnetic field.It needs our further continuous observations until covering the next reversal of solar polarity.
引文
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[12] Ginzburg, V. L., & Syrovatskii, S. I., "The Origin of Cosmic Rays", Pergamon Press. New York, 1964
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[28]吴含荣,利用ASγ实验寻找银道面弥散γ射线辐射,博士学位论文,中国科学院高能物理所,2006
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[30]http://www.mpi-hd.mpg.de/hfm/HESS/
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[32]http://veritas.sao.arizona.edu/
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[65]Amenomori,M.,et al.,ApJ,672,L53,2008
[66]Venkatesan D.,et al.,Space Sci.Rev.,52,121,1990
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[78]Kazumasa Kawata,Doctor dissertation,Konan University,2004
[79]http://www.ngdc.noaa.gov/geomagmodels/IGRFWMM.jsp
[80]Ivanov,A.A.,et al.,JETP Lett.,69,288-293,1999
[81]周远,何会海,木均,高能物理核物理,29,549-554,2005
[82]Glen Cowan,Statistical Data Analysis,Clarendon Press,1998
[83]朱永生,实验物理中的概率和统计(第二版),科学出版社,2006
[84]李惕碚,实验的数学处理,科学出版社,1983
[85]Amenomori,M.et al.,ApJ,626,L29,2005
[86]李爱凤,利用羊八井ASγ实验研究Multi-TeV宇宙线各向异性及其周期性调制,博士学位论文,山东大学物理学院,2008
[87]张毅,利用羊八井ASγ实验研究Multi-TeV宇宙线各向异性,博士学位论文,中国科学院高能物理所,2008
[88]Lomb,N.R.,Astrophys,Space Sci.,39,447,1976
[89]Scargle,J.D.,ApJ,263,835,1982
[90]A.-F.Li et al.,Nuc.Phys.B,175-176,529-532,2008
[91]Hoyt,D.V.& Schatten,K.H.,"Group sunspot numbers:a new solar activity reconstruction",Sol.Phys.,179 189-219,1998
[92]Solanki,S.K.,Inhester,B.& Sch(u|¨)ssler,M.,Rep.Prog.Phys.,69,563,2006
[93]李宗伟、肖兴华,《天体物理学》,高等教育出版社,2003
[94]http://www.swpc.noaa.gov/SolarCycle/index.html
[95]Bilenko,I.A.,Astronomy & Astrophysics,396,657,2002
[96]Harvey,K.L.,& Recely,F.,Sol.Phys.,211,31,2002
[97]Kota,J.et al.,Proc.30th Int.Cosmic Ray Conf.(Mexico City),Vol.1(SH),589-592,2007
[98]Munakata,K.,et al.,arXiv:0811.0422v2,2008
[99]Nagashima,K.,et al.,Nuovo Cimento C,12,695,1989