Computation of magnetic gradients due to three-dimensional bodies

Thc expressions of magnetic gradients due to 3-D homogeneous magnetized polyhedra are systematically derived and presented, fronr which the forward problem of magnetic gradients of an arbitrary shaped geological body is solved. It is shown that in the rotation of coordinate systems there is an essential difference between the transformation of magnetic fields and that of their gradients. In a 2-D coordinate system a unified transformation formula of any order gradients can he derived, hut cannot in the 3-D case. The calculations of synthetic models show the correctness of the expressioils or magnetic gradients. Project supported by the National Natural Science Foundation of China.