Sun–Earth geometry, geomagnetic activity, and planetary F2 layer ion density: Part I: Signatures of magnetic reconnection

Abstract

Our previous quantitative analyses have shown that geomagnetic activity and planetary ion density of the F2 layer of the ionosphere seem to share the same parent cause, the solar wind, whose entry into geospace is controlled by the Sun–Earth geometry. The thrust of this paper is four fold: (a) to establish the reality of this not clearly recognized connection, (b) to demonstrate that geomagnetic activity varies seasonally with three separate and independent components, viz. a semiannual, an annual and a Sun–Earth-distance determined component, all of which can be accurately derived from solar–terrestrial geometry alone, (c) to evaluate the contribution of each of these components which, taken together, appear to represent the steady-state signatures of the mechanism of magnetopause reconnection, and (d) to highlight the fact that the currently used planetary geomagnetic indices are deficient and therefore need to be revised. Since detailed understanding of the precise mechanism of the entry of solar wind energy into geospace is still lacking, no mechanism is suggested to show how solar wind energy is transported to the F2 layer (including low and equatorial latitudes). Magnetospheric electric fields, precipitation of energetic neutrals produced through charge exchange reactions with ions in the ring current and radiation belt particles, Joule heating, etc., may all be involved, but the energy for all such processes still comes from the solar wind. Apart from the three components of the reconnection mechanism mentioned above, a steady component due to the viscous interaction mechanism should also be present.