The Electric Charge of Snow Flakes

[摘要] In the winter season of 1955, the electric charge of snow flakes was individually measured simultaneously with the atmospheric field intensity and the size of snow flakes, using a vacuum tube electrometer, Wulf's electrometer and filter papers respectively. The shape of snow flakes was also observed by the microphotographic method. The following results were obtained.i) When the field gradient was steep, the sign of charge on snow flakes was generally the opposite of that of the prevailing field. Under the weak field, the sign was changeable.ii) The steeper the field gradient and the larger the size of snow flakes was, the larger the charge on them was.iii) The charge was extremely large while the field gradient was rapidly changing, in other words, when the string which showed the gradient was vibrating. The vibrating phenomenon of the string may perhaps represent the existence of a strong turbulence.iv) No special relations were observed between the sign of electric charges and the crystal form.Considering those results, it is supposed that the snow flakes carry electric charges mainly as a result of the selective ion capture under an atmospheric field similar to what happens in the case of raindrops, and on that mechanism are superposed the other effects, that is to say, the friction or disruption of snow flakes.

[学科分类] 大气科学