Modelling the predicted density profile along a spicule from magneto-seismology. The data points are the measured change in average density along the spicule. The red dash line is a normalised density profile (H_e) for the ambient plasma, designed as a simplified model of the classic hydrostatic solar atmosphere. The blue dash-dot lines show two different normalised internal (spicule) density profiles (H_s,1,H_s,2). The solid black lines show the average normalised density profiles calculated using the different internal density profiles.