Figure 8. Final total field anomalies obtained by correlation filtering and averaging the correlated output of the four maps in Figure 7 continued on a spherical Earth to 430 km altitude.

 Separation of lithospheric, external, and core components of the south polar geomagnetic field at satellite altitudes*

Douglas Alsdorf, Ralph von Frese1, Jafar Arkani-Hamed2, and Hallan C. Noltimier1

1Dept. of Geological Sci. and Byrd Polar Research Center, Ohio State Univ., Columbus, OH

 2Dept. of Earth and Planetary Sci., McGill Univ., Montreal, Quebec, Canada

 *Published in Journal of Geophysical Research, v.99, B3, pp. 4655-4668, 1994

 Abstract. We present a new approach to producing scalar Magsat magnetic anomaly maps based on correlation coefficient filtering and the use of almost all of the available orbits. Our method differs from earlier techniques with respect to the following: (1) Passes are selected based on their variance properties rather than planetary indices such as Kp. (2) The core field model is least squares fit to individual passes and subsequently removed instead of subtracting the model directly. This technique replaces band pass filtering and polynomial trend removal methods. (3) Each selected pass is sorted geographically and by local time, placed into one of four different altitude bands, and correlation coefficient filtered with the two adjacent passes. The filtering is the second step toward isolating the static lithospheric signal from the more dynamic external field signals. (4) Least squares collocation is used to grid the correlated passes; subsequently, the dawn and dusk maps are also correlation filtered providing another step toward removal of external fields. (5) The four resultant total field maps are continued to a common altitude and again correlation filtered for the static lithospheric anomalies. (6) The filtered results are then averaged together to provide a new total field map of the lithosphere south of 40 degrees south latitude. Our total field map differs from previous efforts over the crustal blocks of West Antarctica. We obtained a positive anomaly over Edward VII Peninsula, extending into the Byrd subglacial basin and obtained a negative anomaly over the Ellsworth Mountains and parts of the Byrd subglacial basin. Also, a positive anomaly extending from the Ross Sea to offshore Wilkes Land is present in our map; however, this feature is absent in other maps. Positive anomalies marking the Weddell Sea in previous efforts are not present in our map. Prominent external field anomalies in the quadrant offshore of Wilkes Land are presnt in all previous efforts; however, these signatures are reduced in our total field map. This map significantly advances efforts for the identification and interpretation of magnetic anomalies of the south polar lithosphere.

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