Charging of ice-vapor interfaces: applications to thunderstorms

[摘要] The build-up of intrinsic Bjerrum and ionic defects at ice-vapor interfaces electricallycharges ice surfaces and thus gives rise to many phenomena including thermoelectricity,ferroelectric ice films, sparks from objects in blizzards, electromagnetic emissionsaccompanying cracking in avalanches, glaciers, and sea ice, and charge transfer duringice-ice collisions in thunderstorms. Fletcher's theory of the ice surface in equilibriumproposed that the Bjerrum defects have a higher rate of creation at the surface than inthe bulk, which produces a high concentration of surface D defects that then attract ahigh concentration of OH^- ions at the surface. Here, we add to this theory the effect of amoving interface caused by growth or sublimation. This effect can increase the amountof ionic surface charges more than 10-fold for growth rates near 1 mms^-1 and can extend the spatial separation of interior charges in qualitative agreement with manyobservations. In addition, ice-ice collisions should generate sufficient pressure to meltice at the contact region and we argue that the ice particle with the initially sharper pointat contact loses more mass of melt than the other particle. A simple analytic model ofthis process with parameters that are consistent with observations leads to predictedcollisional charge exchange that semiquantitatively explains the negative chargingregion of thunderstorms. The model also has implications for snowflake formation,ferroelectric ice, polarization of ice in snowpacks, and chemical reactions in icesurfaces

[学科分类] 大气科学