arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2008.04319astro-ph.SR
收藏

凌日活动区太阳作为恒星的光谱辐照度观测

Sun-as-a-star Spectral Irradiance Observations of Transiting Active Regions

Shin Toriumi, Vladimir S. Airapetian, Hugh S. Hudson, Carolus J. Schrijver, Mark C. M. Cheung, Marc L. DeRosa

摘要:

主要的太阳耀斑容易发生在与大型、复杂、动态演变的太阳黑子相关的活动区大气中。这表明不仅在可见光中而且在紫外线和X射线中监测星点的演变对于了解恒星耀斑的起源和发生的重要性。为此,我们使用各种全盘面天气观测资料,对不同类型的凌日活动区进行了光谱辐照度分析。目标事件是一个孤立的太阳黑子,一尘不染的plage,并在长期安静的太阳条件下,从过去的十年中选择新兴的通量。结果表明,当黑子位于中央子午线时,可见光连续谱和太阳总辐照度变暗,而在太阳边缘附近变亮,对色球层敏感的紫外波段与光球层总无符号磁通量的变化有很好的相关性; EUV和软X射线的振幅随着特征温度的增加而增加,其光变曲线是平顶的,这是由于它们对光学薄日冕的敏感性;过境的无斑在可见光辐照度下不显示变暗,而新兴的通量在中央子午线周围的所有光变曲线中产生不对称。这里描述的多波长太阳作为一颗恒星的研究表明,日冕和光球光变曲线之间的这种时间滞后有可能探测恒星黑子上方日冕磁场的范围。此外,对过渡区温度敏感的EUV波长有时会显示出反相变化,这可以用于诊断星点周围的等离子体。

英文摘要:

Major solar flares are prone to occur in active region atmospheres associated with large, complex, dynamically-evolving sunspots. This points to the importance of monitoring the evolution of starspots, not only in visible but also in ultra violet (UV) and X-rays, in understanding the origin and occurrence of stellar flares. To this end, we perform spectral irradiance analysis on different types of transiting solar active regions by using a variety of full-disk synoptic observations. The target events are an isolated sunspot, spotless plage, and emerging flux in prolonged quiet-Sun conditions selected from the past decade. We find that the visible continuum and total solar irradiance become darkened when the spot is at the central meridian, whereas it is bright near the solar limb; UV bands sensitive to the chromosphere correlate well with the variation of total unsigned magnetic flux in the photosphere; amplitudes of EUV and soft X-ray increase with the characteristic temperature, whose light curves are flat-topped due to their sensitivity to the optically thin corona; the transiting spotless plage does not show the darkening in the visible irradiance, while the emerging flux produces an asymmetry in all light curves about the central meridian. The multi-wavelength sun-as-a-star study described here indicates that such time lags between the coronal and photospheric light curves have the potential to probe the extent of coronal magnetic fields above the starspots. In addition, EUV wavelengths that are sensitive to the transition-region temperature sometimes show anti-phased variations, which may be used for diagnosing plasmas around starspots.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑