Global Venus-Solar Wind Coupling and Oxygen Ion Escape

The present-day Venusian atmosphere is dry, yet, in its earlier history a significant amount of water evidently existed. One important water loss process comes from the energy and momentum transfer from the solar wind to the atmospheric particles. Here, we used measurements from the Ion Mass Analyzer onboard Venus Express to derive a relation between the power in the upstream solar wind and the power leaving the atmosphere through oxygen ion escape in the Venusian magnetotail. We find that on average 0.01% of the available power is transferred, and that the percentage decreases as the available energy increases. For Mars the trend is similar, but the efficiency is higher. At Earth, the ion escape does not behave similarly, as the ion escape only increases after a threshold in the available energy is reached. These results indicate that the Venusian induced magnetosphere efficiently screens the atmosphere from the solar wind.

Automated summary

Research indicates that an important process of losing water in Venusian atmosphere is due to the energy and momentum transfer from the solar wind to atmospheric particles. Furthermore, under the Venusian induced magnetosphere, only an average of 0.01% of available power is transferred through oxygen ion escape, with the percentage decreasing as available energy increases.