On the Earth's paleo-magnetosphere for the late Hadean eon

Simulations of the terrestrial paleo-magnetosphere for early stages of the solar system are of particular importance for studying the evolution and mass loss of the Earth's atmosphere. Within this presentation, we will present simulations of the paleo-magnetosphere of the Earth for the late Hadean, i.e. for ~4.1 billion years ago. These were performed with an adapted version of the Paraboloid Magnetospheric Model (PMM) of the Skobeltsyn Institute for Nuclear Physics of the Moscow State University, which serves as an ISO standard for the magnetosphere . As an input parameter, the new measurements of the paleomagnetic field strength by Tarduno et al., 2015, are taken. These data from zircons between 3.3 billion and 4.2 billion years old vary between 1.0 and 0.12 of today's equatorial field strength. Available data at ~4.1 billion years ago are among the lowest field strength values. Another input into the adapted PMM is the solar wind pressure, which was derived from a newly developed solar/stellar wind evolution model, which is strongly dependent on the rotation rate of the early Sun. Our simulations of the terrestrial paleo-magnetosphere with the adapted PMM show that for the most extreme case of a fast rotating Sun and a paleomagnetic field strength with 0.12 of today's value, the stand-off distance of the magnetopause rs shrinks significantly down from today's 10-11 R_E to 3.43 R_E (i.e. 2.43 R_E above the Earth's surface, where R_E is the Earth's surface). Even for the least extreme case - i.e. the same magnetic field strength as that of today and a slow rotating Sun - rs shrinks down to 8.23 R_E. Another outcome of the modelling is that the polar cap was significantly broader ~4.1 billion years ago than today.These results have implications for the early terrestrial atmosphere. Since the EUV flux during the late Hadean eon was significantly higher, the exobase of a nitrogen dominated atmosphere would most probably have reached the magnetopause, leading to enhanced atmospheric erosion. However, a significantly higher amount of CO₂ during the late Hadean than at present-day may have prevented atmospheric loss in such a scenario. First results of these erosion processes will be presented within this presentation.