论文标题
Prendergast磁场的稳定性
The Stability of Prendergast Magnetic Fields
论文作者
论文摘要
大型主序列中的对流在其核心中产生大规模的磁场，随着它们在红色巨型分支发展时持续存在。这些场的残余物可能采用Prendergast磁场的形式，Prendergast磁场是多背和环形场成分的组合，这些组件有望相互稳定。以前的分析和数值计算在短时间内没有发现Prendergast领域不稳定的证据。在本文中，我们提出了数值模拟，这些模拟显示了该磁场的长时间线性不稳定。我们发现不稳定性对边界条件的变化是强大的，并且不通过强稳定的分层稳定下来。不稳定性是电阻不稳定性，生长速率对电阻率具有幂律的依赖性，在这种电阻率下，生长速率随着电阻率的降低而降低。我们通过将幂律推断为电阻率的恒星值来估计恒星中不稳定性的生长速率。不稳定性足够快，可以比恒星进化时间尺度短路上的磁场稳定，这表明prendergast场不是恒星中磁场研究中使用的好模型。
Convection in massive main sequence stars generates large scale magnetic fields in their cores which persists as they evolve up the red giant branch. The remnants of these fields may take the form of the Prendergast magnetic field, a combination of poloidal and toroidal field components which are expected to stabilize each other. Previous analytic and numerical calculations did not find any evidence for instability of the Prendergast field over short timescales. In this paper, we present numerical simulations which show a long timescale, linear instability of this magnetic field. We find the instability to be robust to changes in boundary conditions and it is not stabilized by strong stable stratification. The instability is a resistive instability, and the growth rate has a power-law dependence on the resistivity, in which the growth rate decreases as the resistivity decreases. We estimate the growth rate of the instability in stars by extrapolating this power-law to stellar values of the resistivity. The instability is sufficiently rapid to destabilize the magnetic field on timescales shorter than the stellar evolution timescale, indicating that the Prendergast field is not a good model to use in studies of magnetic fields in stars.
