Solar-Wind Structure
Solar-Wind Structure
复制标题
太阳风结构
DOI：
10.1093/acrefore/9780190871994.013.19
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
M. Owens
中科院分区：
文献类型：
--
作者：
M. Owens
炽热的太阳大气层不断地向太空扩张，形成太阳风，太阳风拖曳着太阳的磁场。这就在星际介质中产生了一个空洞，延伸到远远超过外行星的地方，在这个空洞中，太阳磁场占主导地位。虽然太阳大气层被加热的物理机制仍然存在争议，但由此产生的太阳风可以很容易地理解为热而稠密的太阳大气层和冷而稀薄的星际介质之间的压力差。这导致了太阳风的加速，在到达地球轨道之前很久就变成了超音速。太阳风携带的磁场的大尺度结构是阿基米德螺旋，这是由于太阳风的径向流远离太阳，以及磁足点随太阳表面旋转。然而，在这个相对简单的图景中，有一系列的子结构，在所有可观察的时间和空间尺度上。太阳风流动在很大程度上具有双峰的特征。“快”风来自开放的磁场区域，这些区域与太阳表面只有一个连接。另一方面，“慢”风似乎来自封闭磁场区域附近，其两端都与太阳相连。快速风和慢速风的相互作用导致了太阳风压缩和膨胀的模式，这些模式扫过地球。在这种相对稳定的流动结构中，太阳物质的大规模爆发进一步扰乱了条件。在较小的尺度上，湍流漩涡会造成太阳风条件的不可预测的变化。这些太阳能-风能结构引起了极大的兴趣，因为它们会引起空间天气，可能对空间和地面技术产生不利影响，并对空间人类构成威胁。
The hot solar atmosphere continually expands out into space to form the solar wind, which drags with it the Sun’s magnetic field. This creates a cavity in the interstellar medium, extending far past the outer planets, within which the solar magnetic-field dominates. While the physical mechanisms by which the solar atmosphere is heated are still debated, the resulting solar wind can be readily understood in terms of the pressure difference between the hot, dense solar atmosphere and the cold, tenuous interstellar medium. This results in an accelerating solar-wind profile which becomes supersonic long before it reaches Earth orbit. The large-scale structure of the magnetic field carried by the solar wind is that of an Archimedean spiral, owing to the radial solar-wind flow away from the Sun and the rotation of the magnetic footpoints with the solar surface. Within this relatively simple picture, however, is a range of substructure, on all observable time and spatial scales. Solar-wind flows are largely bimodal in character. “Fast” wind comes from open magnetic-field regions, which have a single connection to the solar surface. “Slow” wind, on the other hand, appears to come from the vicinity of closed magnetic field regions, which have both ends connected to the Sun. Interaction of fast and slow wind leads to patterns of solar-wind compression and expansion which sweep past Earth. Within this relatively stable structure of flows, huge episodic eruptions of solar material further perturb conditions. At the smaller scales, turbulent eddies create unpredictable variations in solar-wind conditions. These solar-wind structures are of great interest as they give rise to space weather that can adversely affect space- and ground-based technologies, as well as pose a threat to humans in space.