时间中的太阳：活动与环境
The Sun in Time: Activity and Environment
摘要：
太阳的磁场活动在其主序星期稳步下降。虽然太阳光球的亮度在4.6 Gyr前太阳到达主序星时比现在低30%，但它的快速旋转产生了增强的磁活动;色球层、过渡区和日冕中的磁加热过程分别引起大约10、100和1000次紫外线、极紫外线和X射线发射，现在的水平，从年轻的太阳模拟恒星推断。此外，加速的高能粒子的产生率比现在的太阳耀斑高出几个数量级，而且一股更强大的风从太阳逃逸出来，弥漫了整个太阳系。年轻太阳的辐射和粒子流增强的后果对太阳系行星和卫星的演化可能是严重的。高能辐射和太阳风与上层行星大气的相互作用可能导致了大量大气成分的逃逸。金星目前干燥的大气层和火星稀薄的大气层可能是早期太阳高能辐射照射和加热的产物。高水平的磁活动也推断为前主序太阳。在这些阶段，高能辐射和粒子与最终形成行星的环日盘的相互作用非常重要。高能粒子在陨石中留下的痕迹和陨石包裹体中异常的同位素丰度比可能为一个高度活跃的前主序太阳提供证据。本文综述了与年轻太阳的磁活动及其与环境的相互作用有关的各种问题。
英文摘要：
(abridged) The Sun's magnetic activity has steadily declined during its main-sequence life. While the solar photospheric luminosity was about 30% lower 4.6 Gyr ago when the Sun arrived on the main sequence compared to present-day levels, its faster rotation generated enhanced magnetic activity; magnetic heating processes in the chromosphere, the transition region, and the corona induced ultraviolet, extreme-ultraviolet, and X-ray emission about 10, 100, and 1000 times, respectively, the present-day levels, as inferred from young solar-analog stars. Also, the production rate of accelerated, high-energy particles was orders of magnitude higher than in present-day solar flares, and a much stronger wind escaped from the Sun, permeating the entire solar system. The consequences of the enhanced radiation and particle fluxes from the young Sun were potentially severe for the evolution of solar-system planets and moons. Interactions of high-energy radiation and the solar wind with upper planetary atmospheres may have led to the escape of important amounts of atmospheric constituents. The present dry atmosphere of Venus and the thin atmosphere of Mars may be a product of early irradiation and heating by solar high-energy radiation. High levels of magnetic activity are also inferred for the pre-main sequence Sun. At those stages, interactions of high-energy radiation and particles with the circumsolar disk in which planets eventually formed were important. Traces left in meteorites by energetic particles and anomalous isotopic abundance ratios in meteoritic inclusions may provide evidence for a highly active pre-main sequence Sun. The present article reviews these various issues related to the magnetic activity of the young Sun and the consequent interactions with its environment.
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