Investigating the Influence of Open Crustal Magnetic Field Regions on the Martian Ionosphere

在太阳系中寻找生命与寻找水密切相关，水在地球上大量存在，但在我们太阳系中的其他“类地”行星（即金星和火星）上相对稀缺。由于它们的密度和距离太阳的距离大致相似，类地行星很可能都是由早期太阳星云中大致相似的物质形成的，目前观察到的差异是每个行星不同的长期演化的结果。在火星的例子中，大约40亿年前磁力发电机的停止和导致的行星主磁场的崩溃被认为是大气挥发物损失的主要因素，如水和二氧化碳。这是由于行星磁场对大气和表面环境的屏蔽效应。地球磁场通常将太阳风保持在距离大气层和电离层大约十个行星半径的距离处。然而，在火星的情况下，由于没有明显的磁场，太阳风可以直接进入大气层/电离层，导致挥发物（如水）从行星环境流失到行星际空间。这项研究将调查火星表面附近的强地壳磁场区域（火星原始磁场的残余）与太阳风之间的相互作用。在地壳磁场大致垂直的地区，太阳风可以进入大气层和电离层，在那里它被认为会引起加热。这种加热很可能是火星快车航天器在强近垂直地壳场区域上观测到的火星电离层凸起的原因，并可能导致大气物质的上涌“喷泉”。这些物质可以与太阳风相互作用，并从行星上消失，导致火星大气层的持续侵蚀。拟开展的研究将使用最初用于研究近地空间环境的数字建模技术，并将其应用于火星非常不同的大气层、电离层和磁场。将开发一个计算机模型，以解决与时间有关的连续性、动量和能量平衡方程，这些方程沿沿着简化的尖点状磁场线计算火星电离层中常见的一些离子种类和电子的密度、场向通量和温度。这项研究的结果可以通过与火星轨道航天器（如欧空局的火星快车）返回的数据进行比较加以验证，并将对即将进行的火星探测任务（包括ExoMars）、火星环境的演变和更广泛的外星生物学研究产生重要影响。

The hunt for life in the solar system is intimately linked to the search for water, found in abundance on Earth, but relatively scarce on the other 'Earth-like' planets in our solar system (i.e. Venus and Mars). Given their broadly similar densities and distances from the Sun, it is likely that the Earth-like planets were all formed from broadly similar material in the early solar nebula and that the currently observed differences are a result of the differing long-term evolution of each planet. In the case of Mars, the cessation of a magnetic dynamo and the resulting collapse of the planet's main magnetic field about 4 billion years ago are thought to have been major factors in the loss of atmospheric volatiles, such as water and carbon dioxide. This is due to the shielding effect a planetary magnetic field confers to the atmosphere and surface environment. The Earth's magnetic field typically holds the solar wind at a distance of around ten planetary radii from the atmosphere and ionosphere. However, in the case of Mars, the absence of a significant magnetic field has allowed the solar wind direct access the atmosphere/ionosphere and resulted in the loss of volatiles (such as water) from the planetary environment to interplanetary space. This study will investigate the interaction between regions of strong crustal magnetic field near the surface of Mars (remnants of Mars' original magnetic field) and the solar wind. In regions where the crustal field is oriented roughly vertically, the solar wind can gain access to the atmosphere and ionosphere, where it is thought to cause heating. This heating is likely to be responsible for bulges observed in the Martian ionosphere over regions of strong near-vertical crustal field by the Mars Express spacecraft and may result in upwelling 'fountains' of atmospheric material. This material can then interact with the solar wind and be ost from the planet, contributing to the continuing erosion of Mars' atmosphere. The proposed research will be accomplished using numerical modelling techniques first used to study the near-Earth space environment and applying them to the very different atmosphere, ionosphere and magnetic field of Mars. A computer model will be developed to solve time-dependent equations of continuity, momentum and energy balance along simplified cusp-like magnetic field lines for the densities, field-aligned fluxes and temperatures of a number of ion species and electrons common in the Martian ionosphere. The outcomes of this research can be validated by comparison with data returned from Mars orbiting spacecraft (e.g. ESA's Mars Express) and will have important implications for the forthcoming Mars exploration missions (including ExoMars), the evolution of the Martian environment and broader studies of exobiology.