How does the presence of a large-scale magnetic field impact the solar wind energy dissipation in the Earth’s upper atmosphere?

The protective effect of a planetary magnetic field on the planet’s atmosphere is still debated. This study focuses on a particular aspect of the chain of processes leading to atmospheric escape: the energy transfer from the solar wind to the upper atmosphere. Magnetized planets are surrounded by a large-scale magnetosphere which has two opposite effects. On the one hand, it efficiently diverts the solar wind so that only a small fraction of the solar wind energy flux that intercepts it eventually ends up being dissipated in the upper atmosphere. On the other hand, a large-scale magnetosphere dramatically increases the area of interaction between the solar wind and the planet and thus the amount of solar wind energy that may potentially be funneled into its upper atmosphere.

In this study, we estimate the solar wind energy flux currently dissipated in the Earth’s upper atmosphere using empirical formulas derived from observations found in the literature. We compare it to the solar wind energy that would intercept the induced magnetosphere of a hypothetical unmagnetized Earth. We show that the solar wind energy dissipated in the upper atmosphere is comparable to -if not higher than- the solar wind energy that would intercept a hypothetical unmagnetized Earth. This result indicates that the Earth's large-scale magnetic field does not protect the Earth’s upper atmosphere but rather increases the solar wind energy deposition.