early Earth’s atmosphere. Below, we first provide context through a discussion of atmospheric loss processes.\

Atmospheric Loss Mechanisms
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Atmospheric loss mechanisms are typically divided into thermal escape stimulated by energetic photons and non-thermal escape associated with the interaction of charged particles. Following this classification, the presence/absence of a magnetic field will influence only non-thermal escape. However, thermal processes are also of importance because they determine whether non-thermal loss is likely to be efficient. Moreover, as we introduce below, under reduced standoff conditions of the early Earth, heating due to solar wind interaction with the atmosphere is possible, and in this case the clear-cut assignment of magnetic field influence to only non-thermal processes becomes less meaningful.

Much can be learned about these atmospheric loss processes by study of planets without internally generated magnetic fields, namely Venus and Mars, and the general interest has expanded in parallel with exoplanet discoveries and considerations of habitability [e.g. @Seager2010]. The limitations of these analogies should also be kept in mind; atmospheric loss processes presently working at Venus and Mars are the result of different evolutionary histories of their respective atmospheres. While analogies should not be taken too far, the physical processes are illustrative, notwithstanding 