Figure 11

Maps of the Z component at the Earth’s surface for the first eigen modes. Maps (centered on the Greenwich meridian) of the Z component at the Earth’s surface for the first four normalized eigen modes, \({\mathcal {Z}}_{1}\) to \({\mathcal {Z}}_{4}\), obtained from the \(\tilde {z}_{n}^{m}\) coefficient series in dipole coordinates. They represent 70.6% (top left), 9.4% (top right), 5.2% (bottom left), and 4.5% (bottom right) of the \(\tilde {z}_{n}^{m}\) variances. For each mode, the color scale is saturated at the maximum value of the mode.