Earth

Abstract

Modern Earth models are constrained by an inertia coefficient y* = J₂/H = 0.3308 which leads to a so-called ‘hydrostatic’ flattening f_hyd ≈ 1/299.9. The latter is in rather large disagreement with the observed flattening f ≈ 1/298.3. The authors show that a more satisfactory value of the inertia coefficient for constraining a standard Earth model is y ≈ 0.332, consistent with a hydrostatic flattening of about 1/298.6. The change of the value of the inertia coefficient from about 0.331 to about ≈ 0.332 significantly alters the density structure of the core, notably the density jump at the inner core boundary. It brings, as a by-product, the hydrostatic values of J₂ and H to better agreement with the observed values than is presently thought, and most probably leads for the Slichter mode to a period of much longer than 5.42 h, which is the value computed for PREM. (52 Ref.)