Neutralized solar wind ahead of the Earth's magnetopause as contribution to non-thermal exospheric hydrogen

In a most recent paper by Qin and Waldrop (2016) it had been found that the scale height of hydrogen in the upper exosphere of the Earth, especially during solar minimum conditions, appears to be surprisingly large. This indicates that just during minimum conditions when exobasic temperatures should be small, large exospheric H-scale heights predominate. They thus seem to indicate the presence of a non-thermal hydrogen component in the upper exosphere. We estimate what fraction of such expected hot hydrogen atoms could have their origin from protons of the shocked solar wind ahead of the magnetopause converted into energetic neutral atoms (ENAs) via charge exchange processes with normal atmospheric, i.e. exospheric, hydrogen, in a first step evaporating from the exobase into the trans-magnetopause plasma region. As we show here, dependent on the sunward location of the magnetopause, these types of non-thermal hydrogen atoms will become dominant over exobasic hydrogen at heights between 10 and 90 exobase radii.