| 其他摘要 | A solar filament （also called solar prominence）is composed of a magnetic structure that floats in the hot and tenuous corona and the partially ionized plasma, which is about 100 times denser/cooler than their coronal surroundings. The coronal mass ejections (CME) and solar flares are the main driver of the space weather and always believed to be closely associated with filament eruptions. However, so far, the reason why the cool and dense filament can exist in the hot and tenuous corona is still a question that has not been fully resolved. Magnetic fields are considered to be central to maintaining filament existence in the coronal surroundings. Therefore, measuring the magnetic field of filaments to obtain their three-dimensional (3D) magnetic structure is key to better understand their structure, evolution and eruption. Unfortunately, only on the photosphere can magnetic field be routinely measured and the magnetic field in the upper solar atmosphere is very difficult to measure directly. In the most cases, the 3D coronal magnetic field is obtained by extrapolating the measured photospheric magnetic field.Though the traditional magnetic field extrapolation methods can obtain the magnetic structures of the filaments that locate in the strong field region in the most cases, they always fail for the filaments in the weak field region. In this paper, by the regularized Biot-Savart laws method, we successfully constructed a 3D overall magnetic configuration for an large-scale, horse-shoe-like filament located in a decaying, diffuse and weak field. It is found that there are three regions with significantly different magnetic field strength within it, namely, the kernel region that possesses the strongest magnetic field, the outermost region that has the weakest field, and the middle region that has an intermediate field strength. At the same time, the model reveals a correspondence between the cold materials of filament and magnetic dips, namely, the colder component of the materials is prone to distribute in the magnetic dips. In addition, a new formation mechanism of barbs is confirmed, i.e., the barbs of the filament are a natural consequence of the deformation of a magnetic flux rope (MFR) and not anchored to the photosphere.Then, the process and mechanism of the filament eruption are further investigated in this paper. We found that before the eruption, the filament split into three branches with the same chirality as it, two low-lying branches and a high-lying branch. By analysing the splitting process in detail, we suggest that the pre-eruption splitting is induced by a reconnection between the magnetic field of MFR and newly emerging magnetic field. In the mean time, to the best of our knowledge, this is the first unambiguous observational evidence for the pre-eruption splitting of MFR induced by the reconnection between the magnetic field of MFR and newly emerging magnetic field. After the splitting, the filament erupted. And we find that the two low-lying parts survived the eruption, still located in the source region, while the high-lying part successfully escaped, producing a fast CME and a C1.2 flare, indicating that the filament experienced a parital eruption.However, the observations of the partial eruption presented here can be interpreted neither by the classical “double-decker filament” model nor the “partially-expelled-flux-rope” model. Therefore, the event provides new observational constraints on the construction of the new models for partial eruptions. At the same time, by analysing the kinematics of the process of the eruption and calculating the decay index of the background magnetic fields, we suggest that catastrophe (or torus instability) is the eruption mechanism of the filament. |
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