Theory of Ion Collection in the D-region by a Rapidly Moving Blunt Probe Or Mass Spectrometer PDF Download

Author: Lee W. Parker
Publisher:
ISBN:
Category : D region
Languages : en
Pages : 132

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Book Description
The theory of ion collection at the center of a moving electrically charged blunt-electrode (probe) in the ionospheric D region is considered at high velocities such that the boundary layer is thin. The stagnation-point boundary-layer analysis of Sonin (1967) is reviewed where diffusion, mobility, and convection are coupled within the thin boundary layer at infinity Debye length. A critical parameter is the ion Péclet number P, which is essentially equal to the flow Reynolds number. When the voltage is large compared with (kT/e) square root P, the attracted-ion current is given by the simple linear mobility relation where the current is proportional to the voltage, independent of the flow. Associated with this proportionality is the fact that the attracted-ion concentration is the same at the edge of the boundary layer as it is at infinity. At finite Debye length, the current can depend on the flow and can depend nonlinearly on the voltage. The nonlinearity is associated with a reduction in the attracted-ion concentration at the edge of the boundary layer, due to the presence of space charge. A charge-layer model is used for the space-charge analysis in which the layer (or sheath) is assumed thick compared with the boundary layer but thin compared with the probe radius. Diffusion is neglected, but convection and mobility are included. The nature of the repelled particles must be considered. If the repelled particles are ions, the linear mobility current-voltage relation holds for a restricted range of voltages, independent of the flow. For higher voltages, the relation becomes nonlinear and depends on the flow.