Observations of magnetic clouds, within interplanetary coronal mass ejections (ICMEs), are often well described by flux rope models. Most of these assume either a cylindrical or toroidal geometry. In some cases, these models are also capable of accounting for non-axisymmetric crosssections but they generally all assume axial invariance. It can be expected that any ICME, and its flux rope, will be deformed along its axis due to influences such as the solar wind. In this work, we aim to develop a writhed analytical magnetic flux rope model which would allow us to analytically describe a flux rope structure with varying curvature and torsion so that we are no longer constrained to a cylindrical or toroidal geometry. In this first iteration of our model we will solely focus on a circular cross-section of constant size. We describe our flux rope geometry in terms of a parametrized flux rope axis and a parallel transport frame. We derive expressions for the axial and poloidal magnetic field components under the assumption that the total axial magnetic flux is conserved. We find an entire class of possible solutions, which differ by the choice of integration constants, and present the results for a specific example. In general, we find that the twist of the magnetic field locally changes when the geometry deviates from a cylinder or torus. This new approach also allows us to generate completely new types of in situ magnetic field profiles which strongly deviate from those generated by cylindrical or toroidal models.
Analysis of the Helical Kink Stability of Differently Twisted Magnetic Flux Ropes
磁通量绳（MFR）通常被认为是控制螺旋度从太阳到日光层的传输的磁性结构。它们在螺旋状组织的磁结构中夹带一个受限的等离子体，并能够引起地磁活动。最惠国制度的形成、演变和扭曲分布是引起激烈辩论的问题。虽然到目前为止已经提出了不同的扭曲轮廓，但还没有一个被彻底探索。这项工作的目的是提出一个理论研究的条件下，具有不同的扭曲配置文件是扭结稳定的，从而揭示了上述方面的一些光。磁场根据Nieves-Chinchilla等人（Astrophys. J. 823，27，2016）以及Lundquist和Gold-Hoyle模型，并且用基于Linton、Longcope和Fisher（Astrophys. J. 469，954，1996）。结果进行了讨论，在MFR旋转，磁力，反向手征的情况下，和整个日光层的膨胀，除其他外，提供了一个理论背景，以提高目前的理解的内部磁场配置的日冕物质抛射（CME）。帕克太阳探测器或太阳轨道飞行器等新任务获得的数据将有机会通过观察比以往任何时候都更接近太阳的MFR来探索这些结果和想法。
