以香港為重點，我們對於地表和地下中由地球圈內因子所引致的宇宙射線變化進行了研究。 / 借用圖像重建演算方法，我們定立了一種可於格狀排列的宇宙射線探測器觀測中重塑宇宙射線分佈的方法，並將其用於香港仔隧道實驗室的渺子探測器中。其結果表明地形對地下宇宙射線分佈的影響。 / 在地面上，我們用微擾蒙地卡羅方法研究了大氣變化對地表宇宙射線的影響。由此我們得到了一考慮到所有高度的空氣密度以還原大氣變化對地表宇宙射線影響的修正方案。 / 我們亦演算了宇宙射線粒子在地球磁場內的軌跡，並以探測器收納向量的概念，表達地面儀器所觀測的宇宙射線量與地球以外的原初宇宙射線之關係。 / 最後，藉我們對地球圈內做成宇宙射線變化的眾因子之認識，我們試圖還原它們的作用，以使我們能於地表宇宙射線觀測中探測地外原初宇宙射線的變化。我們的結果表明，在地表宇宙射線中的晝夜變化，有部分是由宇宙中的原初宇宙射線淨流引起。 / Cosmic ray (CR) variations of terrestrial origin were examined, with focus on Hong Kong at both the surface and underground. / Using image reconstruction algorithm, we developed a method to reconstruct CR distribution with measurement from a gridded CR detector, which we then applied to the muon tracker in the Aberdeen Tunnel Lab. The result demonstrated the eect of landscape on underground CR distribution. The good agreement between the measured CR distribution and MUSIC simulation validates the use of such simulation for other underground laboratories. / At the surface, we used perturbative Monte Carlo method to study the effect of atmospheric variations on surface CR counts. The result was a correction scheme to eliminate atmospheric variation in surface CR counts that took the air density at all height levels into consideration. / We also used particle tracing techniques to study the motion of CR particles in Earth’s magnetic field, and how CR counts from surface detectors are related to primary CR beyond Earth through the concept of detector acceptance vector. / With our understanding of CR variations of terrestrial origin, we attempted to undo their effects, and probe primary CR with surface CR observations. Our results suggested that parts of the diurnal variation in surface CR count are related to net streaming in the primary CR. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chan, Yat Long = 在香港的宇宙射線變化研究 / 陳日朗. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 91-95). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Chan, Yat Long = Zai Xianggang de yu zhou she xian bian hua yan jiu / Chen Rilang. / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.3 / Chapter 2.1 --- Primary and secondary cosmic ray --- p.3 / Chapter 2.2 --- General review on CR variation --- p.5 / Chapter 2.2.1 --- Variation in time --- p.5 / Chapter 2.2.2 --- Variation in directions --- p.6 / Chapter 2.3 --- CR variation of extra-terrestrial origin --- p.6 / Chapter 2.3.1 --- Forbush decrease --- p.6 / Chapter 2.3.2 --- CR co-rotation with sun --- p.7 / Chapter 2.3.3 --- CR variations and periodic solar activities --- p.8 / Chapter 2.3.4 --- Anisotropy of galactic origin --- p.9 / Chapter 2.4 --- CR variations of geomagnetic origin --- p.9 / Chapter 2.4.1 --- Geomagnetic cut off at different latitudes and longitudes --- p.9 / Chapter 2.4.2 --- East-West asymmetry --- p.10 / Chapter 2.4.3 --- Time variations of geomagnetic cut-off --- p.10 / Chapter 2.5 --- CR variations of atmospheric origin --- p.12 / Chapter 2.6 --- CR variations from lab overburden --- p.14 / Chapter 2.7 --- Round Up --- p.15 / Chapter 3 --- Muon directional variations in Aberdeen Tunnel Lab --- p.17 / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.1.1 --- The Aberdeen Tunnel Lab --- p.17 / Chapter 3.1.2 --- The muon tracker --- p.18 / Chapter 3.2 --- Simulation of muon directional distribution --- p.19 / Chapter 3.3 --- Reconstruction of muon directional distribution --- p.21 / Chapter 3.3.1 --- Image restoration analogy --- p.21 / Chapter 3.3.2 --- Damped Richardson-Lucy deconvolution algorithm --- p.23 / Chapter 3.3.3 --- Obtaining the PSF --- p.24 / Chapter 3.3.4 --- Reconstruction result --- p.25 / Chapter 3.4 --- Comparison of simulation and reconstruction --- p.26 / Chapter 3.5 --- Conclusion --- p.29 / Chapter 4 --- Simulating Cosmic Ray variations at Ground Surface --- p.30 / Chapter 4.1 --- Scope of study --- p.30 / Chapter 4.1.1 --- Geomagnetic variation --- p.30 / Chapter 4.1.2 --- Atmospheric variation --- p.31 / Chapter 4.2 --- Layout of Simulation --- p.31 / Chapter 4.3 --- Modelling of Primary CR --- p.32 / Chapter 4.4 --- Modelling of Earth's magnetic field --- p.35 / Chapter 4.5 --- Modelling of atmosphere --- p.36 / Chapter 4.6 --- Modelling of lab overburden --- p.37 / Chapter 4.7 --- Modelling of Physics in cosmic ray cascades --- p.37 / Chapter 4.8 --- Counting considerations --- p.38 / Chapter 4.9 --- Monte Carlo speed up --- p.39 / Chapter 4.9.1 --- Primary particle event biasing --- p.41 / Chapter 4.9.2 --- Weight window technique --- p.41 / Chapter 4.10 --- Differential operator sampling --- p.44 / Chapter 4.10.1 --- Finite perturbation --- p.44 / Chapter 4.10.2 --- In nitesimal perturbation --- p.45 / Chapter 4.11 --- Simulation Result --- p.48 / Chapter 4.11.1 --- Rigidity map at HK --- p.48 / Chapter 4.11.2 --- Zenith angle dependence of muon flux --- p.50 / Chapter 4.11.3 --- Density correction coefficients --- p.51 / Chapter 5 --- Analysis of surface CR data --- p.55 / Chapter 5.1 --- Detector description --- p.55 / Chapter 5.1.1 --- The CUHK Muon Telescope --- p.55 / Chapter 5.1.2 --- The Nagoya Multi-Directional Muon Telescope --- p.56 / Chapter 5.2 --- Characterizing the detectors --- p.58 / Chapter 5.2.1 --- Coupling function for rigidity --- p.60 / Chapter 5.2.2 --- Acceptance vectors of detectors --- p.60 / Chapter 5.2.3 --- Sensitivity towards Atmospheric conditions --- p.64 / Chapter 5.3 --- Time series of surface CR data --- p.65 / Chapter 5.4 --- Diurnal variations in CR data --- p.67 / Chapter 5.5 --- Inferring CR streaming from surface measurement --- p.69 / Chapter 6 --- Conclusion --- p.75 / Chapter A --- Density correction coefficients and averaged atmospheric profile --- p.77 / Chapter B --- Acceptance vector of the detectors --- p.87 / Bibliography --- p.91

published_or_final_version / Physics / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 1987.

Thesis (M.Phil.)--University of Hong Kong, 1987. / Also available in print.

Dissertation (PhD)--University of Arizona, Tucson, Arizona, 2005.

The existence of a Fisk-type heliospheric magnetic field (HMF) is one of the most debated questions in cosmic-ray modulation. Recently, Burger and Hitge [2004] developed a divergence-free Fisk-Parker hybrid magnetic field model to demonstrate the behaviour of cosmic rays in the heliosphere due to such a field. This approach has been refined and the properties of the consequent field are investigated. It is found that randomly directed magnetic field diffusion in and above the photosphere significantly influences the solar magnetic field both at the solar poles and near the polar coronal hole boundary. The solar cycle dependence of this field is investigated, a study which is of particular importance for studies of the long-term behaviour of cosmic rays, such as those undertaken at the SANAE base in Antarctica. The amplitudes of the 26-day recurrent cosmic-ray variations are modelled as function of both latitudinal gradient and heliolatitude and are found to agree qualitatively and in some cases quantitatively with the observational results reported by Zhang 119971 and Paizis et al. 119991. Although magnetic field data do not clearly indicate the existence of the Fisk field [see, e.g., Fursyth et al., 20021, this study supports the existence of a Fisk-type HMF. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2006.

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.

The existence of a Fisk-type heliospheric magnetic field (HMF) is one of the most debated questions in cosmic-ray modulation. Recently, Burger and Hitge [2004] developed a divergence-free Fisk-Parker hybrid magnetic field model to demonstrate the behaviour of cosmic rays in the heliosphere due to such a field. This approach has been refined and the properties of the consequent field are investigated. It is found that randomly directed magnetic field diffusion in and above the photosphere significantly influences the solar magnetic field both at the solar poles and near the polar coronal hole boundary. The solar cycle dependence of this field is investigated, a study which is of particular importance for studies of the long-term behaviour of cosmic rays, such as those undertaken at the SANAE base in Antarctica. The amplitudes of the 26-day recurrent cosmic-ray variations are modelled as function of both latitudinal gradient and heliolatitude and are found to agree qualitatively and in some cases quantitatively with the observational results reported by Zhang 119971 and Paizis et al. 119991. Although magnetic field data do not clearly indicate the existence of the Fisk field [see, e.g., Fursyth et al., 20021, this study supports the existence of a Fisk-type HMF. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2006.

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.