Exploring the causes of exoplanetary atmospheric evaporation

系外行星宜居性的关键决定因素之一是其大气条件。因此，了解在系外行星形成和演化过程中可能影响它们的质量损失机制就变得很重要。这项工作将是开发这一机制的模型。该团队将对现有的模型进行修改，使其适用于围绕类似恒星运行的三颗类似的凌日行星。这三颗行星中有两颗在凌日期间显示出大气蒸发的证据，但第三颗行星没有。这三个世界如此相似，但对大气蒸发的结果却如此不同，可能会为我们提供对行星演化的独特洞察。这项工作将支持一名研究生，并将支持四名女本科生实习生。实习的一部分将包括参加关于科学传播的研讨会。PI还将通过参加南非的达特茅斯外国研究项目进行推广。该团队将修改蒸发系外行星代码(EVE)，包括三种尚未纳入代码的新现象。他们将使用该代码来制作围绕三颗类似恒星：K2-25b、Gl 436b和GJ 3470b的三颗类似系外行星的模型。其中，K2-25b没有观测到大气蒸发，但另外两个有大气蒸发。一旦了解了这些系统，该团队将进行一项参数研究，以评估行星外圈如何在一系列恒星和行星参数范围内受到恒星的影响。特别是，该团队将探索基于粒子的模型与流体动力学代码在全3D恒星风问题上的有效性。它们还将包括行星外圈和恒星风之间的电荷交换产生的拾取质子。以前的模型忽略了这一潜在的粒子源。他们还将明确地对大气氦进行建模，这是以前的模型中没有包括的。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

One of the key determining factors for exoplanet habitability is the condition of its atmosphere. It then becomes important to understand the mass loss mechanisms that might affect exoplanets after their formation and through their evolution. This work will be to develop models of this mechanism. The team will adapt an existing model to three similar transiting planets which orbit similar stars. Two of the three planets show evidence of atmospheric evaporation in their transits, but the third planet does not. These three worlds, so similar but yet with such different results for atmospheric evaporation, might provide a unique insight into planetary evolution. This work will support a graduate student and will support four female undergraduate interns. Part of the internships will include participation in a workshop on science communication. The PI will also conduct outreach by participating in the Dartmouth Foreign Studies Program in South Africa.The team will adapt the Evaporating Exoplanet code (EVE) by including three new phenomena that have not yet been incorporated into the code. They will use the code to produce models of three similar exoplanets around three similar stars: K2-25b, Gl 436b, and GJ 3470b. Of these, K2-25b has not been observed to exhibit atmospheric evaporation, but the other two have. Once these systems have been understood, the team will conduct a parameter study to assess how planetary exospheres are impacted by their stars across a range of stellar and planetary parameters. In particular, the team will explore the efficacy of particle-based models versus hydrodynamic codes for the full 3D stellar wind problem. They will also include pickup protons which result from charge exchange between the planetary exosphere and the stellar wind. Prior models neglected this potential source of particles. They will also explicitly model atmospheric helium, which has not been included in prior models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.