The Solar Wind: A net source or sink for terrestrial mass?

Shortly after the solar wind was first measured by the Second Soviet Cosmic Rocket (Luna 2) in 1959, planetary scientists immediately began wondering if it might be a source of mass for terrestrial atmospheres; perhaps even providing the Earth with all of the hydrogen needed for its oceans (De Turville 1961). This particular idea has been shown not to hold water, moreover, it is now known that the solar wind can drive escape from planetary atmospheres in the form of pick up ions. This presentation highlights an unresolved question: does the solar wind represent a net source or sink of mass for the terrestrial planets? We approach the problem using an ion-kinetic quasi-neutral hybrid (QNH) particle-in-cell (PIC) code called Rhybrid. We simulate the interaction of the solar wind with non-magnetized and weakly-magnetized terrestrial-type planets ranging in size from Mars to super Earth (1.5 R_E). We also vary the ion production rate and dipole moment strength in order to explore the relevant parameter space. We quantify the escape rate of planetary ions (H+ and O+), as well as the accretion rate of solar hydrogen, and present the net mass flux for the different modeled scenarios.