论文标题

太阳能活动的演变

The Evolution of the Solar-Stellar Activity

论文作者

Katsova, Maria

论文摘要

我们对观察结果进行了简要回顾,这是有助于现代思想的恒星活动演变。用于旋转年龄和活性旋转关系的基本定律,使我们能够追踪低质量恒星的活性如何随着居住在主序列上的年龄而变化。我们专注于评估可能是年轻太阳类似物的恒星的活性特性。我们的研究包括对不同年龄段的类似太阳恒星的活动,旋转和磁场的不同示踪剂的联合考虑。我们确定旋转周期,当活性的饱和度变化为不饱和模式时,当形成太阳能活性时:对于G-和K型星,它们分别为1.1和3.3天。这对应于年龄间隔约0.2-0.6 GYR,当时正常的黑子周期开始在早期的阳光下建立。我们讨论了年轻太阳中冠状动脉和色球活性的特性。我们对1350-1750 a频谱范围内的EUV升级的评估表明,早期太阳的远处辐射比当今的太阳的强度高7倍,并且当建立常规的太阳点循环时两倍。对于年轻的太阳,我们可以估计与准稳态流出相关的质量损失率为$ 10^{ - 12} m_ \ odot $/yr。还讨论了对太阳能恒星最大耀斑的观察结果,得出的结论是,最强大的现象发生在饱和活性状态下的快速旋转恒星上。我们对恒星磁场的估计可以评估最大可能的耀斑能量。这可以帮助我们更好地了解过去阳光下极端事件的起源。

We present a brief review of observational results contributing to modern ideas on the evolution of stellar activity. Basic laws, derived for both rotation-age and activity-rotation relationships, allow us to trace how the activity of low-mass stars changes with age during their stay on the main sequence. We focus on the evaluation of the activity properties of stars that could be analogs of the young Sun. Our study includes joint consideration of different tracers of activity, rotation and magnetic fields of Sun-like stars of various ages. We identify rotation periods, when the saturated regime of activity changes to the unsaturated mode, when the solar-type activity is formed: for G- and K-type stars, they are 1.1 and 3.3 days, respectively. This corresponds to an age interval of about 0.2-0.6 Gyr, when regular sunspot cycle began to be established on the early Sun. We discuss properties of the coronal and chromospheric activity in young Suns. Our evaluation of the EUV-fluxes in the spectral range of 1350-1750 A shows that the far-UV radiation of the early Sun was a factor of 7 times more intense than that of the present-day Sun, and twice higher when the regular sunspot cycle was established. For the young Sun, we can estimate the possible mass loss rate associated with quasi-steady outflow as $10^{-12} M_\odot$/yr. The results of observations of the largest flares on solar-type stars are also discussed, leading to conclusion that the most powerful phenomena occur on the fast-rotating stars in the saturated activity regime. Our estimate of the stellar magnetic fields makes it possible to evaluate the maximal possible flare energy. This could help us better understand the origin of extreme events on the Sun in the past.

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