Low-mass stars show evidence of vigorous magnetic activity in the form of large flares and coronal mass ejections. Such space weather events may have important ramifications for the habitability and observational fingerprints of exoplanetary atmospheres. Here, using a suite of three-dimensional coupled chemistry–climate model simulations, we explore effects of time-dependent stellar activity on rocky planet atmospheres orbiting G, K and M dwarf stars. We employ observed data from the MUSCLES campaign and the Transiting Exoplanet Survey Satellite and test a range of rotation period, magnetic field strength and flare frequency assumptions. We find that recurring flares drive the atmospheres of planets around K and M dwarfs into chemical equilibria that substantially deviate from their pre-flare regimes, whereas the atmospheres of G dwarf planets quickly return to their baseline states. Interestingly, simulated O₂-poor and O₂-rich atmospheres experiencing flares produce similar mesospheric nitric oxide abundances, suggesting that stellar flares can highlight otherwise undetectable chemical species. Applying a radiative transfer model to our chemistry–climate model results, we find that flare-driven transmission features of bio-indicating chemical species, such as nitrogen dioxide, nitrous oxide and nitric acid, show particular promise for detection by future instruments.

低质量恒星以大耀斑和日冕物质抛射的形式显示出强烈的磁性活动。这种太空天气事件可能会对系外大气的可居住性和观测指纹产生重要影响。在这里，我们使用一套三维耦合化学-气候模型模拟，探索了随时间变化的恒星活动对环绕G，K和M矮星的岩石行星大气的影响。我们采用了MUSCLES战役和过境系外行星观测卫星的观测数据，并测试了一系列的旋转周期，磁场强度和耀斑频率假设。我们发现，反复出现的耀斑将K和M矮星周围的行星大气驱使到化学平衡状态，从而大大偏离了它们的耀斑前状态，而G矮行星的大气层迅速返回其基准状态。有趣的是，模拟O经历耀斑的贫₂和富O ₂大气会产生相似的中层一氧化氮丰度，这表明恒星耀斑可以突出显示其他无法检测到的化学物种。将辐射转移模型应用于我们的化学-气候模型结果，我们发现耀斑驱动的生物指示化学物种（例如二氧化氮，一氧化二氮和硝酸）的传输特征显示出未来仪器检测的特殊希望。