Electrical phenomena of falling and drifting snow
Pearce, Douglas Campbell
Since the time of Franklin, 1750, it has been known that there is a state of electricity associated with the Earth and its atmosphere. Experiments have shown that a total negative surface charge of the order of 5 x 105 coulombs resides on the Earth. This gives rise to the Earth's normal fair-weather electric field of an average magnitude of approximately 100 volts per meter. Furthermore, the atmosphere has a finite conductivity, so that under the action of this electric field, there is a dissipation current. … Observations from balloon ascents (Wigand, 1) have shown that the Earth's electric field decreases far more rapidly with altitude than that due to a uniform distribution of charge on the surface. This indicates the existence of a free space charge. The distribution of this free space charge determines uniquely, through Poisson's equation, the electrical state of the atmosphere. Thus, a study of this charge distribution is extremely important. Free charges result from conduction in the non-homogeneous atmosphere, and from accelerating forces acting on rain, snow and dust.