The earth's surface has a negative surface charge density of $ 10^{-9}cm^{-2}$. The potential difference of $400\;kv$ between the top of the atmosphere and the surface results (due to low conductivity of the lower atmosphere ) in a current of only $1800\;A$ over the entire globe. If their were no mechanism of sustaining atmosphere field, how much time (roughly) would be required to neutralise the the earth's surface ? (This never happen in practice became there is a mechanism to replenish electric charges namely the continual thunder storms and lighting in different parts of the globe) . Radius of the earth $=6.37 \times 10^6m$
