论文标题
太阳香料的动态扭结不稳定性和横向运动
Dynamic kink instability and transverse motions of solar spicules
论文作者
论文摘要
由于中心力增加，流体动力学喷射不稳定（在圆柱几何形状中M = 1模式），这增加了射流的横向位移。当射流沿着磁场移动时，洛伦兹力会尝试减少位移并稳定亚紫色流动的不稳定性。不稳定性的阈值取决于Alfven Mach数（Alfven和Jet Speeds的比率）。我们建议，动态的扭结不稳定性可能是解释太阳大气中观察到的II型Spicules的横向运动的重要性。我们表明，由于垂直速度和径向方向的Alfven速度的降低，因此在垂直扩展的磁通管的外围上升的Spicules可能会开始。因此，倾斜的Spicules可能更不稳定，并且具有更高的横向速度。在II型Spicules条件下，不稳定模式的周期和增长时间分别为30 s和25-100 s，与结构的寿命相当。这可能表明高速流量和II型Spicules在色球光谱线中的快速消失之间的互连。
Hydrodynamic jets are unstable to the kink instability (m=1 mode in cylindrical geometry) owing to the centripetal force, which increases the transverse displacement of the jet. When the jet moves along a magnetic field, then the Lorentz force tries to decrease the displacement and stabilises the instability of sub-Alfvenic flows. The threshold of the instability depends on the Alfven Mach number (the ratio of Alfven and jet speeds). We suggest that the dynamic kink instability may be of importance to explain observed transverse motions of type II spicules in the solar atmosphere. We show that the instability may start for spicules which rise up at the peripheries of vertically expanding magnetic flux tubes owing to the decrease of the Alfven speed in both, the vertical and the radial directions. Therefore, inclined spicules may be more unstable and have more higher transverse speeds. Periods and growth times of unstable modes in the conditions of type II spicules have the values of 30 s and 25-100 s, respectively, which are comparable to the life time of the structures. This may indicate to the interconnection between high speed flow and rapid disappearance of type II spicules in chromospheric spectral lines.
