Intrinsic and Induced Magnetic Fields of the Terrestrial Planets and Their Influence on Atmospheric Escape and Water Inventory

该提案的总体科学目标是研究类地岩石行星的行星磁场对其大气演化的影响，其中太阳风侵蚀被认为是最重要的。即将进行的调查将解决一个基本问题，即行星磁场，无论是固有的还是感应的，如何有效地保护行星大气不脱水？我们已经知道，氢和氧是最容易从行星电离层中提取出来的元素。有趣的是，在所有类地行星中，地球不仅拥有最多的水，而且拥有最强的行星磁场。一般认为，地球磁层是一个有效的屏障，保护太阳风对整个上层大气的直接冲击和侵蚀。没有这种磁屏蔽的行星（如金星和火星）可能更容易受到大气侵蚀。另一方面，具有内在磁层的行星与太阳风的相互作用更强烈，从而使太阳风的机电能集中到极光区，在极光区，强电流有效地将行星和太阳风等离子体库连接起来，为电离层的加热和侵蚀提供了有利条件。该项目将侧重于对地球、金星和火星的离子和中性原子损失进行比较分析，其依据是火星快车和金星快车航天器的现场测量，并辅以地球轨道卫星的数据以及理论和模拟研究。

The general scientific objective of the proposal is the study the influence of the planetary magnetic fields of the terrestrial rocky planets on their atmospheric evolution where solar wind erosion is regarded as most important. The investigations to be performed will address the fundamental question, how efficiently do planetary magnetic fields, intrinsic or induced, shield planetary atmospheres from dehydration? We know already that hydrogen and oxygen are the elements which are extracted most easily from planetary ionospheres. Intriguingly, of all terrestrial planets, the Earth harbors not only the highest amount of water but also has the strongest planetary magnetic field. It is generally thought that the Earth magnetosphere acts as an effective screen, protecting a direct impact and erosive stroke of solar wind on the entire upper atmosphere. Planets which without such a magnetic shielding (as Venus and Mars) might be more exposed to atmospheric erosion. On the other hand, planets with intrinsic magnetospheres interact energetically more strongly with solar wind allowing a focusing of the electro-mechanical energy from solar wind to the auroral zones, where strong electric currents efficiently link planetary and solar wind plasma reservoirs, providing favorable conditions for heating and erosion of the ionosphere. The project will focus on the comparative analysis of loss of ions and neutral atoms from Earth, Venus and Mars based on in–situ measurements on the Mars Express and Venus Express spacecraft complemented by data from satellites orbiting Earth and theoretical and simulation studies.