Abstract

--- - Since the discovery of the large-scale field-aligned currents it is widely acknowledged that gaps exist between the Region 1 (R1) and Region 2 (R2) currents in which the current values are relatively small as compared to neighboring regions. Assuming that the field-aligned currents are generated by plasma pressure gradients, we analyzed data collected by the THEMIS satellites between 2007 and 2011 to identify regions with very low plasma pressure gradients (pressure plateaus), which could be responsible for the appearance of these gaps. It was found that the pressure profiles with low radial gradients are typically located between 8 and 10 Radii around the Earth. Projections of pressure plateau regions onto ionospheric altitudes, for both individual events and on a statistical basis, coincide with the locations of gaps between Iijima and Potemra field-aligned currents. The role played by identified pressure plateaus in shaping the pattern of large-scale field-aligned currents is discussed. - Field-aligned currents that flow between the magnetosphere and ionosphere along magnetic field lines play a crucial role in magnetosphere-ionosphere interactions. Despite being discovered at the start of the space era, their origins are still subject to debate. In our current study, we have established that the observed gaps between the upward and downward currents correspond to the plateau regions of constant plasma pressure, as obtained using data from the THEMIS mission. This finding provides strong evidence in favor of the generation of field-aligned currents by plasma pressure gradients in the transition region between the dipole and tail-like geomagnetic field. This is a critical piece of information for understanding the global dynamics of Earth's magnetosphere. - During quiet geomagnetic conditions, the regions of plasma pressure plateau are observed in the inner magnetosphereThese regions are located at geocentric distances of 8-10 RE forming a ring surrounding the EarthThe localization of the plasma pressure plateau region and gaps between the Region 1 and 2 currents should be located at the same distance