Micrometeoroid flight in the upper atmosphere: Electron emission and charging

In an earlier paper we discussed the role of thermionic emission in the production of electrons by a micrometeoroid entering the earth's night-side atmosphere. There we confined our attention to fast moving micrometeoroids entering the earth's atmosphere, normally. Here we extend that work to include both faster and slower moving micrometeoroids of low work function entering the earth's atmosphere at several discrete angles. We have also removed several simplifying assumptions from the earlier analysis and also included a new current (which we call the ablation current), which plays a progressively important role in calculating the grain charge with increasing entry speed. As before the present study shows how thermionic emission extends the altitude range of electron emission, with the initial angle of entry playing a crucial role. Even more important is the role of initial entry speed which changes the altitude profile of electron emission not only quantitatively but also qualitatively which provides a clear discriminant between these two classes of micrometeoroids that are designated by their entry speed. Limitations of the present study and proposed future extensions are discussed.