Atmospheric Retention on Demagnetized Earth

Abstract It is commonly claimed that Earth's intrinsic magnetic field protects its atmosphere from being stripped away by the solar wind. We test this claim by analyzing the stability of Earth's atmosphere in the case that the geomagnetic field is turned off. We use a hybrid particle-in-cell code (RHybrid) to simulate the global plasma interaction of demagnetized Earth with the solar wind. We vary the global ionospheric outflow rate, and quantify the resultant planetary ion escape rates (O⁺ and H⁺) and the solar deposition rate (H⁺). We use these results to compute the net mass flux to the atmosphere and find that the solar ion deposition rate can be comparable to planetary ion escape rates. Our results show that under modern solar wind conditions, the mass of the atmosphere on demagnetized Earth is stable within 3% over a billion years, suggesting that Earth's intrinsic magnetic field is unnecessary for atmospheric retention.