Physical reasons and consequences of a three-dimensionally structured heliosphere
Physical reasons and consequences of a three-dimensionally structured heliosphere
复制标题
三维结构日光层的物理原因和后果
DOI：
10.1007/bf01206002
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发表时间：
1991
影响因子：
10.3
通讯作者：
H. Fichtner
中科院分区：
文献类型：
--
作者：
H. Fahr;H. Fichtner
在这篇文章中，我们讨论了太阳和星际起源的原因，这些原因导致了膨胀的太阳风的明显三维结构，从而导致了日光层的全球结构。我们目前对这些结构的观测知识进行了审查，并对所有试图从理论上模拟这些太阳风结构的努力进行了批判性的分析，就其优点和缺陷。这里特别研究的是，通过什么机制可以设想星际印记对太阳风膨胀的实际类型。考虑到这一点，太阳系保持亚磁音速的相对运动是非常重要的。相对于周围的磁化星际介质，对应于磁声马赫数约为0.5。在太阳距离约为100 AU的逆风侧，日球层顶关闭遥远的日球层空腔，并将其打开成一个大的这种相对运动的第一个结果是在顺风侧上的延伸的尾翼。第二个结果是，最有可能引起逆风距离比顺风距离小1/3到2/3的不对称日球激波阵面，这至少引起两个重要的逆风-顺风不对称过程，影响激波下游的超音速太阳风膨胀：异常宇宙线扩散到太阳风中，高能喷流电子起源于激波并向内移动到大约20 AU的内临界点。正如我们将证明的那样，这两个过程都影响着20 AU以上的太阳风膨胀，然而，与顺风半球相比，逆风半球更有效。在20天文单位以内的区域，其他机制正在运作，将太阳风膨胀的星际印记进一步向下游传播到内日光层，因为在这里，即使是原始的太阳风电子，鉴于太阳风的整体速度，也表现为亚音速等离子体成分，可以通过适当的失谐来修改太阳风的解决方案。我们给出了这些影响的定量估计。关于太阳风膨胀到逆流环境星际介质的理论，目前的理论尝试的一些缺陷被确定为阻碍星际对实际太阳风解决方案的影响可以变得可见。因此，我们的结论是，有一个明确的需要三维和时间依赖的太阳风模型与自由流出的几何形状，考虑到太阳风等离子体的多谐性与不同的本征模的扰动传播。
In this article we have discussed reasons both of solar and of interstellar origin giving rise to a pronounced three-dimensional structure of the expanding solar wind and thus of the global configuration of the heliosphere. Our present observational knowledge on these structurings is reviewed, and all attempts to theoretically model these solar wind structures are critically analysed with respect to their virtues and flaws. It is especially studied here by what mechanisms interstellar imprints on the actual type of solar wind expansion can be envisaged. With concern to this aspect it hereby appears to be of eminent importance that the solar system maintains a relative motion with a submagnetosonic velocity of about 23km/sec with respect to the ambient magnetized interstellar medium corresponding to a magnetosonic Mach number of about 0.5.A heliopause closing the distant heliospheric cavity within a solar distance of about 100AU on the upwind side and opening it into an largely extended tail on the downwind side results as a first consequence from this relative motion. As a second consequence an asymmetric heliospheric shockfront with upwind distances smaller than downwind distances by ratios between 1/3 and 2/3 is most likely provoked which gives rise to at least two important upwind-downwind asymmetric processes influencing the supersonic solar wind expansion downstream from the shock: the anomalous cosmic ray diffusion into the solar wind, and high energetic jet electrons originating at the shock and moving inwards up to an inner critical point at around 20AU. As we shall demonstrate both processes are influencing the solar wind expansion beyond 20AU, however, more efficiently in the upwind hemisphere as compared to the downwind hemisphere. In the region inside 20AU other mechanisms are operating to propagate the interstellar imprint on the solar wind expansion further downstream into the inner heliosphere because here even the original solar wind electrons, in view of the solar wind bulk velocities, behave as a subsonic plasma constituent which can modify the solar wind solutions by means of an appropriate detuning of the circumsolar electric polarisation field. We give quantitative estimates for these effects.What concerns the theory of a solar wind expansion into a counterflowing ambient interstellar medium, some flaws of the present theoretical attempts are identified impeding that the interstellar influence on the actual solar wind solutions can become visible. We thus conclude that there is a clear need for three-dimensional and time-dependent solar wind models with a free outflow geometry taking into account the multisonicity of the solar wind plasma with different eigenmodes for a perturbation propagation.