We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolut...We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolution. Specifically, in the cases of traditional periodic boundary(PB) and fully-opened boundary(OB) conditions, the evolutions are quite similar before the system achieves the fastest reconnection rate. However, differences emerge between the two cases afterward. In the PB case, the reconnection electric field experiences a rapid decline and even becomes negative, indicating a reversal of the reconnection process. In contrast, the system maintains a fast reconnection stage in the OB case. Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases. In the electron density depletion layer and the dipolarization front region, a larger proportion of suprathermal electrons are produced in the OB case. Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases. However, in the OB case, they can also be generated in the electron holes along the separatrix. Before the reverse reconnection stage, no high-energy electrons are present in the PB case. In contrast, about 20% of the electrons in the thin and elongated electron current layer are high-energy in the OB case.展开更多
With one-dimensional （l-D） hybrid simulations we investigate the nonlinear evolu- tion of the ion cyclotron waves excited by the H＋ and He2＋ temperature anisotropies, and analyze the evolution by using the wavelet...With one-dimensional （l-D） hybrid simulations we investigate the nonlinear evolu- tion of the ion cyclotron waves excited by the H＋ and He2＋ temperature anisotropies, and analyze the evolution by using the wavelet analysis method. The results show that the proton cyclotron waves with the dominant frequency higher than the helium gyro-frequency （ΩHe = 0.5Ωp, with Ωp and ΩHe the proton and helium gyro-frequencies respectively ） are firstly excited, and then the helium cyclotron waves with the dominant frequency lower than the helium gyro-frequency are excited. The relation of our simulation results to the BIF（bifurcated） （there are two peaks in the wave spectrum： one above and one below ΩHe） and CON（continuous） （continuous spectrum from 0.1 Ωp to 1.0 Ωp） wave spectra observed in the magnetosheath are discussed.展开更多
Previous particle-in-cell simulations have evidenced that supercritical, quasi-perpendicular shocks are non-stationary. By separating the incident ions into reflected （R） and directly transmitted （DT） parts, we in...Previous particle-in-cell simulations have evidenced that supercritical, quasi-perpendicular shocks are non-stationary. By separating the incident ions into reflected （R） and directly transmitted （DT） parts, we investigate the ion distributions in a non-stationary perpendicular shock. The upstream ion distributions have two parts corresponding to the R and incident ions respectively, while the R ions have higher energy. The downstream ions have a core-ring distribution. The core and ring parts correspond to the DT and R ions, respectively. The ion distributions depend largely on the non-stationary shock structure. The percentage of the reflected ions cyclically varies in time with a period equal to the shock self-reformation cycle, and the number of the R ions increases with the steepness of the shock ramp.展开更多
基金the support from the Key Research Program of the Chinese Academy of Sciences(No.ZDBSSSW-TLC00105)the National Key R&D Program of China(No.2022YFF0503200)+1 种基金National Natural Science Foundation of China(Nos.41974173 and 42274224)the Youth Innovation Promotion Association,Chinese Academy of Sciences(No.2019066)。
文摘We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolution. Specifically, in the cases of traditional periodic boundary(PB) and fully-opened boundary(OB) conditions, the evolutions are quite similar before the system achieves the fastest reconnection rate. However, differences emerge between the two cases afterward. In the PB case, the reconnection electric field experiences a rapid decline and even becomes negative, indicating a reversal of the reconnection process. In contrast, the system maintains a fast reconnection stage in the OB case. Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases. In the electron density depletion layer and the dipolarization front region, a larger proportion of suprathermal electrons are produced in the OB case. Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases. However, in the OB case, they can also be generated in the electron holes along the separatrix. Before the reverse reconnection stage, no high-energy electrons are present in the PB case. In contrast, about 20% of the electrons in the thin and elongated electron current layer are high-energy in the OB case.
基金supported by National Natural Science Foundation of China (Nos.40725013,40674093)the Open Research Program Foundation of State Key Laboratory for Space Weather,Chinese Academy Sciences
文摘With one-dimensional （l-D） hybrid simulations we investigate the nonlinear evolu- tion of the ion cyclotron waves excited by the H＋ and He2＋ temperature anisotropies, and analyze the evolution by using the wavelet analysis method. The results show that the proton cyclotron waves with the dominant frequency higher than the helium gyro-frequency （ΩHe = 0.5Ωp, with Ωp and ΩHe the proton and helium gyro-frequencies respectively ） are firstly excited, and then the helium cyclotron waves with the dominant frequency lower than the helium gyro-frequency are excited. The relation of our simulation results to the BIF（bifurcated） （there are two peaks in the wave spectrum： one above and one below ΩHe） and CON（continuous） （continuous spectrum from 0.1 Ωp to 1.0 Ωp） wave spectra observed in the magnetosheath are discussed.
基金Supported by the National Natural Science Foundation of China under Grant Nos 40874075, 40725013 and 4094093, and the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCX2-YW-N28.
文摘Previous particle-in-cell simulations have evidenced that supercritical, quasi-perpendicular shocks are non-stationary. By separating the incident ions into reflected （R） and directly transmitted （DT） parts, we investigate the ion distributions in a non-stationary perpendicular shock. The upstream ion distributions have two parts corresponding to the R and incident ions respectively, while the R ions have higher energy. The downstream ions have a core-ring distribution. The core and ring parts correspond to the DT and R ions, respectively. The ion distributions depend largely on the non-stationary shock structure. The percentage of the reflected ions cyclically varies in time with a period equal to the shock self-reformation cycle, and the number of the R ions increases with the steepness of the shock ramp.
