标题： 双流体重联喷流在重力分层大气中 显示英文标题

标题： Two-fluid reconnection jets in a gravitationally stratified atmosphere

摘要： 在太阳重力分层的大气中，密度随高度呈指数下降，因此电离等离子体与中性粒子之间的碰撞耦合也减少。在这里，我们研究离子和中性粒子之间的碰撞在大气不同高度发生的重新连接过程中的作用。我们进行了由局部电阻率引起的磁重联模拟，在重力分层的大气中，我们改变初始重联X点的高度。我们比较了磁流体动力学（MHD）模型和两种双流配置：一种是根据局部等离子体参数计算碰撞耦合，另一种是降低耦合，从而使碰撞效应增强。在分层大气中的模拟显示，在强耦合情况下，MHD和双流模拟具有相似的结构。然而，当碰撞效应增加以达到典型的参数区域时，我们发现了一种非线性失控不稳定性，这将电流片（CS）两侧的等离子体-中性密度分开。随着碰撞效应的增加，速度上的初始解耦加热了中性粒子，并建立了非线性反馈，使中性粒子迁移到CS外部，取代向CS中心聚集的带电粒子。重联速率在0.1左右达到最大值，对于两种重联高度都相似，并且与所有三个模型中使用的局部增强电阻率一致。我们模拟末期附近观察到的等离子体形成初期阶段受主重联点的流出影响，而不是受碰撞影响。我们为MHD和双流模型合成了光学薄发射，当使用带电粒子密度而不是总密度时，可以显示出非常不同的演化。 显示英文摘要

摘要： The density decreases exponentially with height in the solar gravitationally stratified atmosphere, therefore the collisional coupling between the ionized plasma and the neutrals also decreases. Here, we investigate the role of collisions between ions and neutrals on the reconnection process occurring at various heights in the atmosphere. We perform simulations of magnetic reconnection induced by a localized resistivity in a gravitationally stratified atmosphere, where we vary the height of the initial reconnection X-point. We compare a magnetohydrodynamic (MHD) model and two two-fluid configurations: one where the collisional coupling is calculated from local plasma parameters and another where the coupling is decreased, so that collisional effects are enhanced. Simulations in a stratified atmosphere show similar structures in MHD and two-fluid simulations with strong coupling. However, when collisional effects are increased to attain representative parameter regimes, we find a nonlinear runaway instability, which separates the plasma-neutral densities across the current sheet (CS). With increased collisional effects, the initial decoupling in velocity heats the neutrals and this sets up a nonlinear feedback where neutrals migrate outside the CS, replacing charged particles which accumulate towards the center of the CS. The reconnection rate has a maximum value around 0.1, similar for both reconnection heights, and is consistent with the use of a localized enhanced resistivity used in all three models. The initial stages of plasmoid formation, observed near the end of our simulations, is influenced by the outflow from the primary reconnection point, rather than by collisions. We synthesize optically thin emission for both MHD and two-fluid models, which can show a very different evolution when the charged particle density is used instead of the total density.