The currents flowing between the Earth and ionosphere are numerically calculated. We solve the current continuity equation by two methods: the first method is to solve ϕ in ∇ ⋅ J = ∇ ⋅ (σ∇ϕ) = 0, where σ is atmospheric conductivity and ϕ is the electric potential, and the second method is to solve the current potential Ψ in ∇ ⋅ J = − ∇2Ψ = 0 by assuming J = − ∇Ψ, a curl-free current density. Two solutions of ∇ ⋅ J = 0 for current flow in the atmosphere between Earth surface and ionosphere are compared in this reply. The differences of two results are <4%, which may be partly caused by the numerical errors in the presence of large variations in the σ profile. The current potential can provide a good approximation for upward currents that flow into the ionosphere. In addition, we compare two models for the current flow from lithosphere to atmosphere: (a) two charge layers embedded in the lithosphere and (b) a dynamo in the lithosphere. The presence of a dynamo in the lithosphere for Model (b) can lead to the presence of current and electric field in the atmosphere and hence in the ionosphere. In Model (a), the electrostatic charge layers in the lithosphere cannot lead to the presence of electric field in the atmosphere.
- lithosphere-atmosphere-ionosphere coupling