LOW-ENERGY PARTICLE LAYER OUTSIDE THE PLASMA SHEET BOUNDARY - COMMENT

We consider the mapping schemes where the plasma sheet boundary layer (PSBL) in the tail is projected to the auroral oval as inconsistent with the available data. We conclude that the low-energy layer (LEL) structure discovered by Parks et al.(1992) at the outer edge of the PSBL is consistent with the mapping scheme by Feldstein and Galperin (1985) where the boundary plasma sheet (BPS ) (which includes the PSBL proper and presumably can also include the newly discovered LEL) is mapped to the polar diffuse aurora (PDA). Note that this definition of BPS plasma domain in the tail (which includes only the PSBL and LEL, as distinct from the central plasma sheet (CPS)), which projects to the bulk of the region of the discrete aurora, or the auroral oval), differs substantially from the BPS as defined by Winningham et al.(1975). In Winningham's definition the BPS refers to the structured accelerated electrons precipitation region at ionospheric altitudes, and it sometimes was improperly interpreted as indicating the mapping of the nightside auroral oval to the plasma sheet outer boundary.