背景太阳风数值模拟的熵守恒格式

背景太阳风研究是根据行星际扰动传播情况预测空间天气状况的基础，磁流体（MHD）模拟是背景太阳风研究的重要手段.采用一种新的数值计算方式，利用Ideal GLM-MHD将计算过程中产生的磁场散度以c_h的速度向计算区域外传播，从而消去磁场散度；重构部分使用受约束的最小二乘法，将磁场散度作为约束条件添加到重构中，进一步对重构后的磁场梯度进行修正；通量计算采用满足热力学第二定律的熵守恒格式，该格式能够确保在计算过程中熵不增，保证数值稳定.研究结果表明，该方法应用于太阳风数值模拟的求解得到了更加稳定的结果. 

Numerical Simulation for Solar Wind Background by Entropy Conservation Scheme

Background solar wind is a key factor for interplanetary disturbance propagation. Magnetohydrodynamic (MHD) simulation is an important tool for background solar wind study. In this paper an entropy conservation scheme is adopted. Ideal GLM-MHD is used to handle the magnetic divergence. The divergence of the magnetic field generated during the calculation is propagated outside the calculation domain with the maximum characteristic speed of MHD system. With the analytical divergence-free condition of magnetic field as additional constraint condition, the reconstruction of solution variables uses the constrained least squares method. The reconstructed magnetic field gradient is further modified by the way of iteration. The flux calculation adopts an entropy conservation scheme which satisfies the second law of thermodynamics. This formulation can ensure that the entropy does not increase in the calculation process, and the numerical stability can be guaranteed. The results show that numerical simulation for solar wind background by entropy conservation scheme can obtain more stable results.