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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >A new shock fitting procedure for the MHD Rankine-Hugoniot relations for the case of small He2+ slippage
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A new shock fitting procedure for the MHD Rankine-Hugoniot relations for the case of small He2+ slippage

机译：一个新的冲击磁流体动力拟合过程兰金雨贡纽关系的情况小何+滑动

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To study MHD shocks in space, it is important to find the shock frame of reference from the observed plasma and magnetic field parameters. These shock parameters have to satisfy the Rankine-Hugoniot relations. In this study we present a novel procedure for shock fitting of the one-fluid anisotropic Rankine-Hugoniot relations and of the time difference between two spacecraft observations in the case of small He2+ slippage. Here, a Monte-Carlo calculation and a minimization technique are used. The observed variables including the upstream and downstream magnetic fields, plasma densities, plasma betas, plasma anisotropies, W (the difference between the downstream and upstream velocities, W ≡ V 2 ? V 1), and Δt (the time difference between two spacecraft observations) are used in our procedure where V is defined as the center of mass velocity of plasmas. A loss function based on a difference between the calculated and the observed values is defined, and the best fit solution is found by searching for the minimum loss function value. For shocks that cannot be fitted well, we introduce two new parameters in the modified RH relations, one in the normal momentum flux and the other in the energy flux equations. These two parameters are interpreted as the equivalent “normal momentum” and “heat” fluxes needed in the RH relations. They provide two degrees of freedom in the system, and their amounts can be estimated from our procedure. Several synthetic shocks are given to verify our procedure. We also apply this procedure to two interplanetary shocks observed by both the WIND and Geotail spacecraft. The results demonstrate that our method works for both the synthetic and the real shocks. We have shown that our method can provide accurate shock normal estimations for perpendicular and parallel shocks as well. Given that our model is based on the RH relations that do not include the effect of alpha particle (He2+) slippage, it can only be applied to the cases with an ignorable slippage pressure tensor. We have investigated the pressure tensor due to alpha particle slippage using the WIND spacecraft data. It is found that in general the slippage pressure is small in comparison with the thermal pressure of the system and can be ignored. Thus our model can be applied to most interplanetary shocks observed near the ecliptic plane. However, when the slippage pressure is large, the magnetic coplanarity theorem is not valid any more. A more general model that involves slippage pressure tensor is a major and important development that is beyond the scope of the present study.
机译：在太空研究磁流体动力冲击,是很重要的找到的冲击的参照系观察到等离子体和磁场参数。这些冲击参数必须满足兰金雨贡纽关系。提出一个新颖的冲击过程拟合的单一流体各向异性兰金雨贡纽关系和时间两个之间的区别飞船观测的小何+滑动。使用最小化技术。变量包括上游和下游磁场,等离子体密度、等离子体贝塔等离子体各向异性,W(之间的区别下游和上游速度,W≡V 2 ?V - 1),Δt(两个之间的时差宇宙飞船观测)是用于我们的过程中V是定义为中心的等离子体的质量速度。在计算和之间的区别观测值的定义,最适合的解决方案是通过搜索发现的最小值损失函数值。安装好,我们引入了两个新的参数修改后的RH关系,正常的动量通量和其他能量通量方程。相当于“正常动力”和“热”RH关系所需的流量。两个自由度系统中,他们的可以从我们的估计过程。给出几种合成冲击来验证我们的过程。星际冲击观测到的风和Geotail飞船。我们的方法在合成和工作真正的冲击。可以提供准确的冲击正常的估计垂直与平行的冲击。我们的模型是基于RH的关系不包括α粒子的影响(何+)滑动,它只能应用于情况下可忽略的下滑压力张量。我们有压力张量由于调查α粒子使用风飞船滑移数据。与热压力比较小系统的压力,可以忽略。我们的模型可以应用于大多数星际冲击黄道平面附近观察到。当滑移压力很大,磁同面性定理是无效的。一般模型涉及到滑动的压力张量是一个主要的和重要的发展超出本研究的范围。

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