J.L. Le Mouel postulated 
J.L. Le Mouel postulated that the secular variation is caused by the Coriolis force effecting the advection of the lines of force in this region, while Zuihong Zou et al. modeled the foundation of this region via diffraction of PKP waves in the region immediately below it. Moreover, even though Sebastian Rost et al. discovered namesake "rigidity zones" found in the demarcation between this region and the one above it, this region bounded on its bottom by the Lehmann discontinuity and on its upper side by the Gutenberg discontinuity is an extremely fluid layer of iron-nickel alloys. Impermeable to S waves, For 10 points, name this layer between the mantle and inner core.
J.L. Le Mouel postulated that the secular variation is caused by the Coriolis force effecting the advection of the lines of force in this region, while Zuihong Zou et al. modeled the foundation of this region via diffraction of PKP waves in the region immediately below it.
{outer} core [prompt on “{core}” until “{inner core}” is read]