A study of rocket measurements of ionospheric currents-V. Modelling rocket profiles of low-latitude ionospheric current

Abstract

Some 25 rocket profiles of the current density of the eastward ionospheric lower current layer close to the magnetic dip equator, one profile of the reverse westward lower current layer at about 5° dip latitude and five profiles of the eastward upper current layer within 0° to about 8° dip latitude have been modelled giving the following results. The parameters of the eastward lower current layer within 0° to 2° dip latitude around local noon are; peak current density normalized to dip equator 10.4 ± 6 A km-2, peak current intensity normalized to dip equator 145 ± 86 A km-2, and half thickness at half of the peak current density 5.7 ± 1 km. The differences in these parameters between the equatorial electrojet in India and Peru are negligible. The parameters of the ionospheric eastward upper current layer around local noon are; peak current density normalized to the dip equator 2.37 ± 0.5 A km-2, peak current intensity normalized to the dip equator 22.1 ± 7 A km-2, and half thickness at half of the peak current density 4.1 ± 2 km. The parameters of the model fitting the rocket profiles extremely well have been provided. The suggestion that the lower eastward and the lower westward current layers constitute the equatorial electrojet, while the upper eastward current layer is the global part of the Sq currents, has been substantiated. This leads to results consistent with spherical harmonic analysis of geomagnetic Sq variations. The first contours of the ionospheric eastward upper current layer density have been presented and they are consistent with the features of the worldwide Sq.