Preprints
https://doi.org/10.5194/angeo-2020-23
https://doi.org/10.5194/angeo-2020-23

  11 May 2020

11 May 2020

Review status: this preprint is currently under review for the journal ANGEO.

A Comparison of Contact Charging and Impact Ionization in Low Velocity Impacts: Implications for Dust Detection in Space

Tarjei Antonsen1, Ingrid Mann1, Jakub Vaverka2, Libor Nouzak2, and Åshild Fredriksen1 Tarjei Antonsen et al.
  • 1Department of Physics and Technology, UiT – The Arctic University of Norway, 9037 Tromsø, Norway
  • 2Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, Prague, 180 00, Czech Republic

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.

Tarjei Antonsen et al.

 
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Tarjei Antonsen et al.

Tarjei Antonsen et al.

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Short summary
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.