Global Magsat anomaly maps at ground level

Four maps of the vertical component of the magnetic anomaly field are derived at ground level from Magsat data at satellite altitude. Measurements performed below and above an altitude of 425 km are treated as two independent datasets by two different methods: (1) a local downward continuation inverse method and (2) a global spherical harmonic decomposition. For each map, one-and two-dimensional energy density spectra are obtained and correlation coefficients are computed. It is shown that anomalies with wavelengths as short as 700 km can be significantly recovered at ground level, corresponding to a ground resolution of 350 km. The improved correlation between anomalies and geodynamic features achieved with downward-continued maps is illustrated with the example of Southeast Asia.