I am trying to understand why is the surface of the earth negative. From the internet search, I found -105 C. I make a sequence according to the conventional model and question at each step. 1. The surface is slightly negative: here I just accept and start. 2. Atmosphere is positive: Some internet source explains that friction of air or water, which seems that it should be net neutral. Only cosmic rays seem to be the reason for positive charge. Am I wrong? 3. 1800A of net electric current: This means the positive ions are coming down bit by bit due to the built in potentail between the surface and the atmosphere. Some explains that it is rain and dust causing 1800A of current. Which is right? 4. If the positive charges reach the surface of the earth, the net charge of the surface of the earth must be already neutral (if the positive ions migrated due to the built in potential) or positive (if the positive ions came with rain and dust). It contradicts #1. 5. If the surface is positive, it is balanced by lightning making the surface "negative" again: how can more electrons come down or positive ions go up more than the potential between the cloud and surface becomes 0? In other words, lower surface of the cloud had electrons and these are recombined by the positive ions from the earth surface. Than the electric field must be 0. Although there are more electrons up in the cloud, they cannot come down to make negative charge on the surface. Could anyone explain clearly? Thanks!