Venus and Mars in the solar wind. A Comparative study over four solar cycles.

具有固有磁场的行星形成了所谓的磁层（行星周围由行星磁场主导的空间），它保护它们的大气层/电离层免受与太阳风磁化等离子体流的直接相互作用和接触。有些行星，如火星和金星，没有固有磁场，它们的大气层/电离层可能与太阳风直接接触。然而，被磁化的太阳风在电离层中产生电流，从而产生磁场，而与固有磁层相比，感应磁层在离行星更近的地方形成。尽管在过去的四个太阳活动周期中，许多航天器收集了大量的原位和遥感数据，但感应磁层的物理性质仍然没有得到充分的探索。本项目将以金星和火星为研究对象，对诱导磁层的形成和特征有一个连贯的认识。观测结果表明，它们的感应磁层结构在太阳极紫外辐射和太阳风的作用下发生了剧烈的变化。将对先前火星和金星任务（先锋金星轨道飞行器（PVO）、金星快车（VEX）、火星全球勘测者（MGS））期间获得的观测数据进行重新评估，并对仍在运行的航天器（火星快车（MEX）、火星大气和挥发物演化（MAVEN））的数据进行分析。该项目将由位于德国Köln的莱茵<s:1>世界环境研究所（RIU）和俄罗斯莫斯科的空间研究所（IKI）的两个研究小组合作共同执行。RIU的团队将通过多仪器分析和PVO、VEX、MGS、MEX和MAVEN航天器进行的观测结果的相关性，重点研究金星和火星电离层。本研究将分析电离层受外部驱动因素（太阳极紫外通量和太阳风）影响的非磁化和磁化电离层状态。这些外部驱动力的大小随日心距离和太阳活动而变化，电离层变弱或变强，这可能显著改变太阳风/电离层相互作用的物理特性。该项目的RIU团队将以观测分析为目标，研究太阳风/电离层相互作用的主要影响，而IKI团队将研究诱导磁层的理论方面，包括磁场堆积机制和行星际磁场在日侧渗透到电离层的机制，磁尾的稳定性和破坏问题。研究结果将适用于其他没有磁场的行星，如冥王星、彗星、有大气层的大卫星，原则上也适用于系外行星。

Planets with an intrinsic magnetic field form so-called magnetospheres (a space around the planet dominated by the planetary magnetic field) which protect their atmospheres/ionospheres from the direct interaction and contact with the magnetized plasma flow of the solar wind. There are planets, like Mars and Venus, which do not posses an intrinsic magnetic field and their atmospheres/ionospheres may have direct contact with the solar wind. The magnetized solar wind, however, creates currents in the ionosphere which induce a magnetic field and an induced magnetosphere is formed much closer to the planet, however, than an intrinsic magnetosphere. Despite a wealth of in-situ and remote sensing data collected by many spacecraft over the past four solar cycles, the physics of induced magnetospheres is still insufficiently explored. This project shall focus on the cases of Venus and Mars in order to get a coherent picture of the formation and characteristics of induced magnetosphere. Observations suggest that the structure of their induced magnetospheres is drastically changed by variations of both the solar EUV radiation and the solar wind. A reevaluation of the observational data obtained during the previous missions to Mars and Venus (Pioneer Venus Orbiter (PVO), Venus Express (VEX), Mars Global Surveyor (MGS)) and an analysis of the data from still operational spacecraft (Mars Express (MEX), Mars Atmosphere and Volatile EvolutioN (MAVEN)) shall be performed. The project shall be jointly performed by a collaboration of the two research groups located at the Rheinisches Institut für Umweltforschung (RIU) in Köln, Germany, and the Institute of Space Research (IKI) in Moscow, Russia. The team at RIU shall focus on the study of Venus and Mars ionospheres by a multi-instrument analysis and correlation of observations performed by the PVO, VEX, MGS, MEX and MAVEN spacecraft. This study shall analyze the unmagnetized and magnetized ionospheric states affected by the external drivers (solar EUV flux and solar wind) onto the ionospheres. The magnitude of these external drivers varies with both heliocentric distance and the solar activity and the ionosphere becomes weaker or stronger which may significantly change the physics of the solar wind/ionosphere interaction. The RIU team in this project shall target the analysis of observational to study the main effects of the solar wind/ionosphere interaction, while the IKI team shall examine the theoretical aspects of the induced magnetospheres including the mechanisms of the magnetic field pile-up and the penetration of the interplanetary magnetic fields into the ionosphere at the dayside, problems of the stability and disruption of the magnetic tail. The results shall have relevance for other planets without magnetic fields like Pluto, comets, large moons with atmospheres and in principle also for exoplanets.