Gravity and pressure‐gradient currents using ionospheric electron density measurements from COSMIC satellites

Abstract

The gravity‐driven and pressure‐gradient currents coexist in the ionosphere, and their effects are significant in there, rather than at the outside of the ionosphere; and can be important while studying the ionospheric currents using low‐Earth‐orbiting (LEO) satellite measurements. Maute and Richmond (2017, https://doi.org/10.1002/2017JA024841) (MR17) have demonstrated that above the F region peak, directions of these two coexisting currents are opposite and the net magnetic effects along the ambient magnetic field are nonsignificant. In the view of the diamagnetic corrections being applied to the LEO magnetic field measurements to account for the pressure‐gradient currents, it is imperative to examine the proposition of MR17. In the present paper, we have estimated the gravity and pressure‐gradient currents, using altitude profiles of electron density obtained from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)‐1 satellite cluster. In order to get the latitudinal profiles of magnetic field variations at a fixed local time (LT) using COSMIC data, it is required to combine either different days at a fixed longitude or all the longitudes on a fixed day, thus compromising with either days or longitudes. It is found that the net magnetic field is significant in the low‐latitude region, which increases with solar flux and decreases with altitude. The magnetic field effects show strong LT dependence and are significant in the noon to evening sector. The comparison of the present estimates with the diamagnetic corrections emphasizes that correcting for only one current can introduce unviable errors and thus supports the suggestion of MR17. Plain Language Summary: In addition to the ionospheric‐dynamo currents, the currents due to gravity and plasma pressure‐gradients flow in the Earth's ionosphere, whose contribution in the ground magnetic field measurements is negligible compared to that of ionospheric‐dynamo. However, considering the magnetic field due to gravity and pressure‐gradient currents present in the ionosphere maybe important while studying the ionospheric currents using low‐Earth‐orbiting (LEO) satellite measurements. Above the F region peak where LEO satellites generally fly, the directions of these two coexisting currents are opposite and the net magnetic field along the ambient magnetic field is nonsignificant. In the view of the diamagnetic corrections being applied to the LEO magnetic field measurements to account for the pressure‐gradient currents, it is imperative to compute the magnetic field effects of these currents using actual observations of ionospheric electron densities. In the present paper, we have estimated the gravity and pressure‐gradient currents, using altitude profiles of electron density obtained from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)1 satellite cluster. The magnetic variations due to these currents are estimated at different heights, latitudes, solar fluxes, and local times