INVESTIGADORES
AVILA Eldo Edgardo
artículos
Título:
A Laboratory Study of Static Charging by Fracture in Ice Growing By Riming
Autor/es:
E. E. AVILA; G. CARANTI
Revista:
JOURNAL OF GEOPHYSICAL RESEARCH
Editorial:
AMERICAN GEOPHYSICAL UNION
Referencias:
Año: 1994 vol. 99 p. 10611 - 10620
ISSN:
0148-0227
Resumen:
Charge transfer by fracture between colliding ice particles is measured using a wind tunnel inside a cold room. The charges were recorded one by one and the mechanics of each collision was studied in detail. The sign of the temperature gradient at a given point of impact on the surface influences the sign of the charge transfer. In this work we extend previous measurements to particles growing by riming. A cylinder growing by riming in a wind tunnel was used as target for collisions at 5~m/s with ice spheres of 100~$mu$m in diameter in a wide range of temperatures. Charge transfers of either sign were also observed here and according to the ambient conditions one of them prevailed on average. The transferences ranged $ pm50$~fC at higher temperatures increasing in magnitude to $-80$~fC at lower ones. There was ample evidence of fragmentation following most of the collisions. The modest impact velocities used, suggest the viability of this kind of charging. A physical model is presented on the microscopical mechanism leading to the asymmetric charging of the fragments. The influence of the growth regime on the production of fragments was also studied. When applied to a thundercloud, the laboratory evidence suggests that the proposed mechanism could operate in a wide range of conditions and even explain some of the in situ observations related to the abundance of ice crystals. Comparisons are made with other experiments on static charging of ice.