| Popis: |
We report on an attempt to examine quantitatively (but indirectly) the classical picture of the global atmospheric electric circuit: namely, the hypothesis that electric currents flowing from global thunderstorms up into the ionosphere (also known as Wilson currents) cause a steady charging of the ionosphere (representing the upper plate of the geocapacitor). For this purpose, we have applied an earlier numerical model of the global ionospheric electrostatic potential. This model consists of a “thin shell” ionosphere at 400 km altitude (i.e., 2D for the electric potential formulated in magnetic field line coordinates) and the global computational region which includes both conjugate ionospheres as separate sub-domains. In this model we account for the interhemispheric field-aligned current densities (which are taken to be equal and opposite at conjugate points) and a realistic distribution of ionospheric conductivity. As a reference, we take the electrostatic potential over the polar regions calculated from an experimental, data-based model of the high-latitude field-aligned currents and then obtain the global (but non-uniform) potential distribution. To study the effects on the global electric circuit, we add into our global model some additional currents to simulate the effect of thunderstorms on this ionospheric shell. Following a quasi-realistic approach, we apply these additional thunderstorm currents over one of the three main thunderstorm active regions: Africa, Asia/Oceania, and America. We find that the eastward electric field in the equatorial ionosphere can be changed by ∼0.1 mV / m . It could be worthwhile to search for such effects in various ionospheric data sets. |
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