| 摘要: | 行星際震波是太空中高能粒子加速的重要來源之一。本研究探討行星際震波的物理特性對離子加速效應的影響，分析 Solar Orbiter 衛星於 2021 至 2023 年間觀測到的 43 起快速震波事件。研究結合磁流體力學（MHD）理論，並運用 Rankine-Hugoniot 關係式進行擬合與統計，定量評估震波參數（如 ρ_d⁄ρ_u、θ_Bn、V_S、M_f 及 β ）與離子通量變化之相關性。
分析結果顯示，在 60 keV 至 6 MeV 能量範圍內，V_S 與 M_f 與離子通量峰值高度正相關，ρ_d⁄ρ_u 則表現為中度正相關，而 θ_Bn 與 β 的相關性則較不顯著。針對不同事件型態（如穩定型、尖峰型、階梯型、預增型）以及不同日心距離（近距離、中距離、遠距離）下的分布進行細部分析，發現各型態事件在參數相關性與能量分布上有顯著差異：尖峰型事件多與 θ_Bn 較大的準垂直震波相關，階梯型與預增型事件則更符合震波擴散加速（DSA）理論預測。隨著日心距離增加，震波能量逐漸耗散，離子加速效率下降，事件型態也發生變化：近太陽區域多為明顯加速特徵（尖峰型、階梯型、預增型），而遠距離則以穩定型事件為主。但無論距離遠近，V_S 越快、M_f 越高的事件，其離子通量峰值提升幅度越大，顯示強震波具有更高能量轉移與粒子加速能力。
;Interplanetary shocks are one of the most important sources of energetic particle acceleration in space. In this study, we investigate how the physical properties of interplanetary shocks influence ion acceleration by analyzing 43 fast shock events observed by the Solar Orbiter spacecraft between 2021 and 2023. The analysis incorporates magnetohydrodynamic (MHD) theory and employs the Rankine-Hugoniot relations for fitting and statistical evaluation, quantitatively assessing the correlations between shock parameters (such as compression ratio, shock angle, shock speed, fast-mode Mach number, and plasma beta) and variations in ion flux.
The results show that, within the energy range of 60 keV to 6 MeV, shock speed and fast-mode Mach number exhibit a strong positive correlation with the peak ion flux, while the compression ratio shows a moderate positive correlation. In contrast, the correlations involving shock angle and plasma beta are less significant. A detailed analysis of different event types (including stable, spiky, step-like, and pre-enhanced types) and their distribution at different heliocentric distances (near, middle, and far) reveals pronounced differences in parameter correlations and spectral distributions. Specifically, spiky events are mostly associated with larger shock angle (i.e., quasi-perpendicular shocks), while step-like and pre-enhanced events are more consistent with predictions from diffusive shock acceleration (DSA) theory. As the heliocentric distance increases, the energy of the shocks dissipates and the efficiency of ion acceleration decreases, resulting in changes in event types: clear acceleration signatures (such as spiky, step-like, and pre-enhanced events) are mainly observed near the Sun, whereas steady events become predominant at larger distances. Nonetheless, regardless of distance, events with higher shock speeds and larger fast-mode Mach numbers exhibit greater enhancements in peak ion flux, indicating that strong shocks have a higher capacity for energy transfer and particle acceleration. |
