论文标题
电子温度各向异性对在强导磁场的存在下无碰撞撕裂模式不稳定性的影响
Impact of electron temperature anisotropy on the collisionless tearing mode instability in the presence of a strong guide field
论文作者
论文摘要
我们得出并分析了由电子惯性驱动的无碰撞撕裂模式生长速率的分散关系，并考虑了强引导场状态下的平衡电子温度各向异性。为此，得出了一个新的Gyrofluid模型并随后简化了，以使分析关系的推导可分析。 The main simplifying assumptions consist in assuming cold ions, neglecting electron finite Larmor radius effects, decoupling ion gyrocenter fluctuations and considering $β_{\perp_e} \ll 1$, with $β_{\perp_e}$ indicating the ratio between the perpendicular electron thermal pressure and the magnetic pressure exerted by the guide field.这种简化的Gyrofluid模型的版本被证明具有非规范性的哈密顿结构。分散关系是通过应用渐近匹配理论获得的，并且不会预测随着垂直和平衡平衡电子温度之间的比率$θ_e$的增强，增长率会提高。这表明与缺乏或中等指导场的情况有显着差异。对于垂直声音LARMOR半径和固定的$β_ {\ perp_e} $的平衡磁剪切长度，我们获得了强导域中的撕裂模式实际上受到了微弱的阻尼，因为$θ_e$增加。在各向同性限制$θ_e= 1 $中，分散关系减少到先前已知的公式。分析预测对显示出非常良好的定量一致性的数值模拟进行了测试。我们还提供了详细的讨论，讨论了派生的分散关系的有效性范围以及不同所采用假设之间的兼容性。
We derive and analyze a dispersion relation for the growth rate of collisionless tearing modes, driven by electron inertia and accounting for equilibrium electron temperature anisotropy in a strong guide field regime. For this purpose, a new gyrofluid model is derived and subsequently simplified to make the derivation of the dispersion relation treatable analytically. The main simplifying assumptions consist in assuming cold ions, neglecting electron finite Larmor radius effects, decoupling ion gyrocenter fluctuations and considering $β_{\perp_e} \ll 1$, with $β_{\perp_e}$ indicating the ratio between the perpendicular electron thermal pressure and the magnetic pressure exerted by the guide field. This simplified version of the gyrofluid model is shown to possess a noncanonical Hamiltonian structure. The dispersion relation is obtained by applying the theory of asymptotic matching and does not predict an enhancement of the growth rate as the ratio $Θ_e$, between perpendicular and parallel equilibrium electron temperatures, increases. This indicates a significant difference with respect to the case of absent or moderate guide field. For an equilibrium magnetic shear length of the order of the perpendicular sonic Larmor radius and at a fixed $β_{\perp_e}$, we obtain that the tearing mode in the strong guide field regime gets actually weakly damped, as $Θ_e$ increases. In the isotropic limit $Θ_e=1$, the dispersion relation reduces to a previously known formula. The analytical predictions are tested against numerical simulations showing a very good quantitative agreement. We also provide a detailed discussion of the range of validity of the derived dispersion relation and of the compatibility among the different adopted assumptions.
