论文标题
VOIGT平衡中近地磁尾的动力气球不稳定
Kinetic Ballooning Instability of the Near-Earth Magnetotail in Voigt Equilibrium
论文作者
论文摘要
长期以来,据信,气球的不稳定性可能是近地磁尾尾巴中实体和当前干扰启动的可能触发机制。然而,在全球且逼真的磁尾配置中,动力学气球模式(KBM)的稳定性尚未得到很好的检查。 In this paper, stability of the KBM is evaluated for the two-dimensional Voigt equilibrium of the near-Earth magnetotail based on an analytical kinetic theory of ballooning instability in the framework of kinetic magnetohydrodynamic (MHD) model, where the kinetic effects such as the finite gyroradius effect, wave-particle resonances, particle drifts motions are included usually through kinetic closures. KBM的生长速率在很大程度上取决于磁场线的僵硬因子$ S $,这又取决于被困电子的影响,有限的离子Gyroradius和带电颗粒的磁漂移运动。 KBM在赤道$β_{eq} $的有限中间范围内不稳定,并且仅在较高$β_{eq} $ ymimime的情况下略微不稳定。有限的离子Gyroradius和被困的电子分数增强了僵硬的因子,该因子倾向于稳定磁尾远离地球的KBM。另一方面,当前的表稀薄破坏了较低的$β_{eq} $制度中的KBM,并在较高的$β_{eq} $制度中稳定KBM。
For a long time, ballooning instabilities have been believed to be a possible triggering mechanism for the onset of substorm and current disruption initiation in the near-Earth magnetotail. Yet the stability of the kinetic ballooning mode (KBM) in a global and realistic magnetotail configuration has not been well examined. In this paper, stability of the KBM is evaluated for the two-dimensional Voigt equilibrium of the near-Earth magnetotail based on an analytical kinetic theory of ballooning instability in the framework of kinetic magnetohydrodynamic (MHD) model, where the kinetic effects such as the finite gyroradius effect, wave-particle resonances, particle drifts motions are included usually through kinetic closures. The growth rate of the KBM strongly depends on the magnetic field line stiffening factor $S$, which is in turn determined by the effects of the trapped electrons, the finite ion gyroradius, and the magnetic drift motion of charged particles. The KBM is unstable in a finite intermediate range of equatorial $β_{eq}$ and only marginally unstable at higher $β_{eq}$ regime for higher $T_e/T_i$ values. The finite ion gyroradius and the trapped electron fraction enhance the stiffening factor that tends to stabilize the KBM in the magnetotail far away from Earth. On the other hand, the current sheet thinning destabilizes KBM in the lower $β_{eq}$ regime and stabilizes KBM in the higher $β_{eq}$ regime.