Excitation of the Slichter mode by collision with a meteoroid or pressure variations at the surface and core boundaries

TL;DR

This paper models Earth's Slichter mode response to various excitations using a normal-mode formalism, revealing that pressure at core boundaries most effectively excites inner-core translational motion.

Contribution

It introduces a comprehensive eigenfunction expansion approach to analyze Earth's free oscillations and response to diverse excitation sources at the Slichter mode period.

Findings

Pressure at core boundaries effectively excites the Slichter mode.

Surface and internal sources have limited impact on the Slichter mode.

The formalism provides a complete Green's function response for different excitations.

Abstract

We use a normal-mode formalism to compute the response of a spherical, self-gravitating anelastic PREM-like Earth model to various excitation sources at the Slichter mode period. The formalism makes use of the theory of the Earth's free oscillations based upon an eigenfunction expansion methodology. We determine the complete response in the form of Green's function obtained from a generalization of Betti's reciprocity theorem. Surficial (surface load, fluid core pressure), internal (earthquakes, explosions) and external (object impact) sources of excitation are investigated to show that the translational motion of the inner-core would be best excited by a pressure acting at the core boundaries at time-scales shorter than the Slichter eigenperiods.