The solar wind interaction with the topside ionospheres of Venus and Mars: A multi-instrument study

虽然太阳风与地球的相互作用是由内在磁场的存在主导的，但金星和火星的大气直接暴露在太阳风流中。对先驱者金星轨道器航天器(1978-1992年)在强烈太阳活动高峰期进行的现场观测导致发现了金星电离层顶(地球上不存在的行星电离层和太阳风系之间的一种尖锐边界)。尽管有了这一发现，但关于太阳风与全球非磁化行星相互作用的许多问题至今仍未得到解答。这一提议将金星快车(2006-2014年)、火星快车(2003-今天)和MAVEN航天器(2014-今天)的观测与全球3-D模型结合起来，以改进我们目前对太阳风与火星和金星相互作用的理解。除了两个行星的主要行星等离子区域外，由于各个航天器的仪器能力，还确定了几个分区域/等离子边界。目前正在讨论，哪些观测描述了同一区域的不同物理特征，哪些观测描述了完全不同的边界。2.建议编制一个数据库，其中载有现场观测到的金星和火星潜在等离子体区域/边界的特征，以分析和澄清改变环境和空间气象条件的各个等离子体区域之间的关系。现场观测受到航天器轨道的限制，无法同时解决观测参数的水平和垂直变化。几乎垂直的电离层电子密度分布的高高度分辨率使无线电掩星成为研究行星太阳风相互作用的宝贵资源，但目前尚未使用。由于几何原因，射电科学观测永远不能与同一时间和同一地点的现场测量同时进行。提出了电离层无线电掩星观测与(1)中提出的等离子体边界数据库的统计和逐轨比较，以确定电离层顶部变率和强电子密度梯度特征(POT)的来源。电离层)在射电掩星观测中可见。无线电掩星观测也被评估为远距离研究行星太阳风相互作用的工具。这项拟议的工作将导致对金星和火星的等离子体边界进行彻底的分析。它将提供新的证据，支持/反对在不断变化的空间天气条件下存在电离层顶。将导出的数据集与金星和火星的3D MHD/混合局部电子密度模型相结合进行相互比较，将有助于更好地理解太阳风与全球未磁化的类地行星的相互作用。

While the solar wind interaction with Earth is dominated by the presence of an intrinsic magnetic field, the atmospheres of Venus and Mars are directly exposed to the solar wind flow. In-situ observations of the Pioneer Venus Orbiter spacecraft (1978-1992) during a strong solar maximum led to the discovery of the Venus ionopause (a sharp boundary between the planetary ionosphere and the solar wind regime which does not exist at Earth). Despite this discovery, many questions about the solar wind interaction with globally unmagnetized planets remain unanswered today. This proposal combines observations from the Venus Express (2006–2014), Mars Express (2003–today) and the MAVEN spacecraft (2014–today) with global 3-D modeling to improve our current understanding of the solar wind interaction with Mars and Venus.1.) In addition to the main planetary plasma regions of both planets several sub-regions/plasma boundaries have been identified due to individual spacecraft instrument capabilities. It is currently under discussion, which observations describe different physical features of the same region and which observations describe completely different boundaries. The compilation of a data base containing the characteristics of the in-situ observed potential plasma regions/boundaries of Venus and Mars is proposed to analyze and clarify the relation between the individual plasma regions for changing environmental and space weather conditions.2.) In-situ observations are constrained by the orbit of the spacecraft, making it impossible to resolve horizontal and vertical changes of the observed parameters simultaneously. The high altitude resolution of the almost vertical ionospheric electron density profiles makes radio occultations a valuable but currently unused resource for the investigation of the planetary solar wind interaction. Because of geometrical reasons, radio science observations can never be performed simultaneously with same-time and same-location in-situ measurements. Proposed are the statistical and the orbit-by-orbit comparison of the ionospheric radio occultation observations with the plasma boundary data base proposed in (1) to determine the origin of the ionospheric topside variability and the strong electron density gradient feature (pot. ionopause) seen in radio occultation observations. Radio occultation observations are also assessed as a tool for the remote investigation of the planetary solar wind interaction.3.) The proposed work will result in a thorough analysis of the plasma boundaries at Venus and Mars. It will provide new evidence for/against the presence of the ionopause during changing space weather conditions. The intercomparison of the derived data sets in combination with 3-D MHD/hybrid + local electron density modeling for Venus and Mars will result in a better understanding of the solar wind interaction with globally unmagnetized terrestrial planets.