Single repeated contact ice charging
Charge transfer in single, repeated collision of ice surfaces. An experimental study of the charging of colliding ice surfaces replicates in part a study (Mason & Dash, 2000, https://doi.org/10.1029/2000JD900104) in which there was qualitative agreement with a prediction of Baker and Dash, (1989, https://doi.org/10.1016/0022-0248(89)90581-2 1994, https://doi.org/10.1029/93JD01633) based on the proposal by Turner and Stow (1984, https://doi.org/10.1080/01418618408236549). However, the magnitude (a few picoCoulombs) of the transferred charge observed by Mason and Dash (2000) was considerably greater, raising doubt that the mechanism of charge transfer is solely a surface-layer effect. The current study examined charge transfer in single collisions between an ice pellet and an ice sheet (instead of two flat surfaces) and its dependence on the common temperature, saturation and environmental pressure. The polarity was consistent with the earlier results in that the more-rapidly growing particle charged positively. The magnitude (also a few picoCoulombs) of the charge transferred increased slightly over an even greater range of temperature (235K to 268K). The sign of the charge transfer is explicable in terms of the relative growth-rate of the contacting surfaces. This result (with surfaces at a common temperature) provides quantitative confirmation of that earlier work (where temperature differentials existed) without the need for postulating (Dash et al, 2001, https://doi.org/10.1029/2001JD900109) collisional melting. It is inferred that the charge is carried in mass transferred between the colliding surfaces, supporting the conjecture by Dash et al (2006, https://doi.org/10.1103/RevModPhys.78.695) that the mass transfer can be driven by differences in curvature, and contradicting the proposition by Baker and Nelson (2002, https://doi.org/10.1016/S1631-0705(02)01408-1) that the transfer between different shapes would be driven from sharp to flat surfaces.