Browsing by Author "Yang, Yan"
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Item A pressure-robust stabilizer-free WG finite element method for the Stokes equations on simplicial grids(Electronic Research Archive, 2024-05-27) Yang, Yan; Ye, Xiu; Zhang, ShangyouA pressure-robust stabilizer-free weak Galerkin (WG) finite element method has been defined for the Stokes equations on triangular and tetrahedral meshes. We have obtained pressure-independent error estimates for the velocity without any velocity reconstruction. The optimal-order convergence for the velocity of the WG approximation has been proved for the L2 norm and the H1 norm. The optimal-order error convergence has been proved for the pressure in the L2 norm. The theory has been validated by performing some numerical tests on triangular and tetrahedral meshes.Item Kinetic Scale Magnetic Reconnection with a Turbulent Forcing: Particle-in-cell Simulations(The Astrophysical Journal, 2023-01-31) Lu, San; Lu, Quanming; Wang, Rongsheng; Li, Xinmin; Gao, Xinliang; Huang, Kai; Sun, Haomin; Yang, Yan; Artemyev, Anton V.; An, Xin; Jia, YingdongTurbulent magnetic reconnection has been observed by spacecraft to occur commonly in terrestrial magnetosphere and the solar wind, providing a new scenario of kinetic scale magnetic reconnection. Here by imposing a turbulent forcing on ions in particle-in-cell simulations, we simulate kinetic scale turbulent magnetic reconnection. We find formation of fluctuated electric and magnetic fields and filamentary currents in the diffusion region. Reconnection rate does not change much compared to that in laminar Hall reconnection. At the X-line, the electric and magnetic fields both exhibit a double power-law spectrum with a spectral break near local lower-hybrid frequency. The energy conversion rate is high in turbulent reconnection, leading to significant electron acceleration at the X-line. The accelerated electrons form a power-law spectrum in the high energy range, with a power-law index of about 3.7, much harder than one can obtain in laminar reconnection.