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首页> 外文期刊>Astrobiology >Modeling Repeated M Dwarf Flaring at an Earth-like Planet in the Habitable Zone: Atmospheric Effects for an Unmagnetized Planet
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Modeling Repeated M Dwarf Flaring at an Earth-like Planet in the Habitable Zone: Atmospheric Effects for an Unmagnetized Planet

机译：模拟在可居住区域中类似地球的行星上反复发生的M矮人爆发：未磁化行星的大气效应

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摘要

Understanding the impact of active M dwarf stars on the atmospheric equilibrium and surface conditions of a habitable zone Earth-like planet is key to assessing M dwarf planet habitability. Previous modeling of the impact of electromagnetic (EM) radiation and protons from a single large flare on an Earth-like atmosphere indicated that significant and long-term reductions in ozone were possible, but the atmosphere recovered. However, these stars more realistically exhibit frequent flaring with a distribution of different total energies and cadences. Here, we use a coupled 1D photochemical and radiative-convective model to investigate the effects of repeated flaring on the photochemistry and surface UV of an Earth-like planet unprotected by an intrinsic magnetic field. As input, we use time-resolved flare spectra obtained for the dM3 star AD Leonis, combined with flare occurrence frequencies and total energies (typically 10~(30.5) to 10~(34) erg) from the 4-year Kepler light curve for the dM4 flare star GJ1243, with varied proton event impact frequency. Our model results show that repeated EM-only flares have little effect on the ozone column depth but that multiple proton events can rapidly destroy the ozone column. Combining the realistic flare and proton event frequencies with nominal CME/SEP geometries, we find the ozone column for an Earth-like planet can be depleted by 94% in 10 years, with a downward trend that makes recovery unlikely and suggests further destruction. For more extreme stellar inputs, O_(3) depletion allows a constant ∼0.1–1 W m~(−2) of UVC at the planet's surface, which is likely detrimental to organic complexity. Our results suggest that active M dwarf hosts may comprehensively destroy ozone shields and subject the surface of magnetically unprotected Earth-like planets to long-term radiation that can damage complex organic structures. However, this does not preclude habitability, as a safe haven for life could still exist below an ocean surface.
机译：了解活跃的M矮星对大气平衡和可居住区地表条件的影响评估类M行星的宜居性至关重要。先前对单个大火炬的电磁辐射和质子对类地大气的影响进行的模型化研究表明，臭氧的长期和长期减少是可能的，但大气得以恢复。然而，这些恒星更现实地表现出频繁爆发，并散布着不同的总能量和节奏。在这里，我们使用耦合的一维光化学和辐射对流模型来研究重复燃烧对不受内在磁场保护的类地球行星的光化学和表面紫外线的影响。作为输入，我们使用从dM3恒星AD Leonis获得的时间分辨耀斑光谱，结合耀斑发生频率和总能量（通常为4年的开普勒光曲线，从10〜（30.5）到10〜（34）erg），来计算dM4耀斑星GJ1243，具有不同的质子事件冲击频率。我们的模型结果表明，重复的仅EM耀斑对臭氧柱深度的影响很小，但是多个质子事件可以迅速破坏臭氧柱。将实际的耀斑和质子事件频率与标称的CME / SEP几何形状相结合，我们发现类地球行星的臭氧柱在10年内可能会减少94％，并且呈下降趋势，这使得恢复的可能性不大，并暗示了进一步的破坏。对于更极端的恒星输入，O_（3）的耗尽使行星表面的UVC恒定为〜0.1–1 W m〜（−2），这可能对有机物的复杂性有害。我们的结果表明，活跃的M矮星宿主可能会全面破坏臭氧层，并使未受磁保护的类地行星的表面遭受长期的辐射，从而可能破坏复杂的有机结构。但是，这并不排除可居住性，因为在海面以下仍可能存在生命安全的避风港。

著录项

  • 来源
    《Astrobiology》 |2019年第1期|64-86|共23页
  • 作者

    Matt A. Tilley; Antígona Segura; Victoria Meadows; Suzanne Hawley; James Davenport;

  • 作者单位

    Department of Earth and Space Sciences, University of Washington|NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team|Astrobiology Program, University of Washington;

    NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team|Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México;

    NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team|Astrobiology Program, University of Washington|Department of Astronomy, University of Washington;

    NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team|Astrobiology Program, University of Washington|Department of Astronomy, University of Washington;

    NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team|Department of Physics and Astronomy, Western Washington University;

  • 收录信息 美国《科学引文索引》(SCI);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    M dwarf; Flares; Stellar activity; aHbitable zone; Planetary atmospheres; Magnetic field;

    机译：m矮人;耀斑;恒星活动;赤裸区域;行星大气;磁场;

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