We consider the mapping schemes where the plasma sheet boundary layer
(PSBL) in the tail is projected to the auroral oval as inconsistent wi
th the available data. We conclude that the low-energy layer (LEL) str
ucture 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 prope
r and presumably can also include the newly discovered LEL) is mapped
to the polar diffuse aurora (PDA). Note that this definition of BPS pl
asma domain in the tail (which includes only the PSBL and LEL, as dist
inct from the central plasma sheet (CPS)), which projects to the bulk
of the region of the discrete aurora, or the auroral oval), differs su
bstantially from the BPS as defined by Winningham et al.(1975). In Win
ningham's definition the BPS refers to the structured accelerated elec
trons 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.