Received: 08 Apr 2020 – Accepted for review: 02 May 2020 – Discussion started: 11 May 2020
Abstract. We investigate the generation of charge during collision of projectiles with sizes below ~ 1 μm and metal surfaces at speeds ~ 0.1 km/s. This corresponds to speeds above the elastic limit and well below speeds where volume ionization can occur. The conditions that we consider apply to dust particles naturally occurring in space and in Earth's upper atmosphere and their direct impacts on rockets, spacecraft, and impacts of secondary ejecta. We introduce a model of capacitive contact charging in which we allow for projectile fragmentation upon impact, and show that this model describes measurements of metal-metal impacts in the laboratory and in-situ measurements of dust in the Earth's atmosphere well. We have considered the utilization of our model for different scenarios in interplanetary space and in Earth's atmosphere. From this discussion we find it likely that our work can be employed in a number of situations where impact velocities are relatively small. Furthermore, we have discussed the thermodynamics of the low velocity solution of shock wave ionization, and conclude that the impurity charging effect utilized in the much used model of Drapatz and Michel (1974) does not sufficiently describe charge generation at impact speeds below a few kilometers per second. Consequently, impact charging at low speeds cannot be described with a Saha-solution.
This paper discusses the charge generation for impacts of nano- to micro-scale dust on metal surfaces at speeds below a few km/s. By introducing a model of capacitive coupling between the dust and the impact surface, we find that at such low speeds, the charge can be dominated by contact charging as opposed to plasma generation.
This paper discusses the charge generation for impacts of nano- to micro-scale dust on metal...