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一个内在的磁场的存在，金星和火星的大气层直接暴露在太阳风流。先锋金星轨道器航天器（1978-1992年）在强烈的太阳活动高峰期进行的现场观测导致发现金星电离层顶（行星电离层和太阳风状态之间的明显边界，在地球上不存在）。尽管有这一发现，关于太阳风与全球非磁化行星相互作用的许多问题今天仍然没有答案。该提案将金星快车（2006-2014），火星快车（2003年至今）和MAVEN航天器（2014年至今）的观测与全球3D建模相结合，以提高我们目前对太阳风与火星和金星相互作用的理解。除了这两颗行星的主要行星等离子体区域外，由于各个航天器仪器的能力，还确定了几个次区域/等离子体边界。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。建议编制一个包含现场观测的金星和火星潜在等离子体区/边界特征的数据库，以分析和澄清单个等离子体区与变化的环境和空间天气条件之间的关系。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剖面的高度分辨率使得无线电掩星成为一种宝贵的，但目前尚未使用的资源，用于行星太阳风相互作用的调查。由于几何原因，无线电科学观测永远无法与同一时间和同一地点的现场测量同时进行。本文提出了利用电离层掩星观测数据与（1）中提出的等离子体边界数据库进行统计和逐轨比较，以确定电离层顶面变率和强电子密度梯度特征（pot.电离层顶）在无线电掩星观测中看到。无线电掩星观测也被评估为远程调查行星太阳风相互作用的工具。拟议的工作将导致对金星和火星等离子体边界的彻底分析。它将提供新的证据，证明在空间气象条件变化期间存在/不存在电离层顶。相互比较的衍生数据集结合3-D MHD/混合动力+本地电子密度建模金星和火星将导致更好地了解太阳风与全球非磁化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.