日冕物質拋射（CMEs）是太陽圈中最高能量的干擾源。它們是一組織良好的磁場結構，它們對太陽圈的干擾是經由與環境磁場和電漿體的相互作用。干擾的強度和類型取決於CME的磁結構和動力學。因此，對其進行良好的估計和/或測量可對太空天氣預報提供更好的幫助 。但是，目前的觀察只能測量探測器位置處的CME磁場，無法提供CME磁場的完整圖像。本研究的目標是確定日冕物質拋射的磁性結構和動力學。方法是通過結合觀測資料和CME模型的預測結果。本研究選擇的模型稱為噴發磁通模型。此模型假設CME是一3D磁通管並符合理想的磁流體動力學體系。CME的整個過程，從啟動開始到最後的傳播階段，可以通過求解同一組方程來計算。不同的CME軌跡可經由調整模型中的參數產生。一旦模型產生與觀察一致的軌跡，參數的值可用於計算CME結構和動力學。模型計算出的1 AU的CME磁場可以與衛星當地測量值比較，以進一步檢查模型的可信度。如果模型預測與觀測到的軌跡以及衛星當地測量值均一致，模型結構可以被認為是實際CME的結構。本研究的結果可與地磁場干擾與CME磁結構之間的關係結合，以用於預測地磁暴的嚴重程度。CME磁通量也可以結合到太陽圈磁通量的演變的計算中以期解決太陽圈磁場隨太陽周期反轉的問題。 ;Coronal mass ejections (CMEs) are the most energetic source of disturbance in the heliosphere. They contain a well-organized magnetic structure, and perturb the space through interactions with ambient magnetic fields and plasma. The strength and types of the disturbances depend on the magnetic structure and dynamics of the CME. Therefore,a good estimate and/or measurement of these two pieces of information can help better prediction of the CME impact on our space weather and better understanding about the CME contribution to the heliospheric magnetic field. However, current observation can only measure the CME magnetic field at the locations of the detectors when they are hit by the CME, and cannot provide a complete picture of the CME magnetic field.The objective of this project is to determine the magnetic structure and dynamics of coronal mass ejections by combining the measurements from observation and predictions from CME model. The model selected for this study is called erupting fluxrope model, which is formulated under the assumption that the CME is a 3D magnetic fluxrope in the regime of ideal magnetohydrodynamics. The entire process of CME, from initiationto the last propagation stage, can be computed by solving a same set of equations. The parameters in the model can be adjusted to produce different CME trajectories. Once the parameters have been adjusted to produce a trajectory consistent with the observation, the values of the parameters can be used to compute the CME structure and the forcesacting on it. The computed CME magnetic field at 1 AU can be compared with the in-situ measurements to further check the validity of the model solution. If the model prediction is consistent with both the observed trajectory and the in-situ measurements, the computed structure can be considered as a good representation of the actual CME structure.In the future, if the relationship between the geomagnetic field disturbance and the CME magnetic flux and field orientation can be found, it can be used in the predicting the severity of geomagnetic storms.The CME magnetic flux can also be incorporated into the computation of the solar cycle evolution of heliospheric magnetic flux.
