Magnetic Anomaly: Magnetized Sphere at the Equator
Now, let's examine the shape of the anomalous magnetic field for the exact same metallic sphere buried at the equator.
At the equator (magnetic), the direction of the Earth's main magnetic field is now horizontal. It still induces an anomalous magnetic field in the metallic sphere, but the orientation of field lines describing the magnetic field are now rotated 90 degrees. As in the previous case, these field lines are indicated by the black lines, and the strength and direction of the anomalous field at the surface of the earth are shown by the blue arrows. Above the sphere, the anomalous magnetic field, Fa, now points in the opposite direction as the Earth's main magnetic field, Fe. Therefore, the total field measured will be less than the Earth's main field, and so upon removal of the main field, the resulting anomalous field will be negative. On either side of the sphere, the anomalous field points in the general direction of the main field and thus reinforces it resulting in total field measurements that are larger than the Earth's main field. Upon removal of the main field contribution, these areas will show positive magnetic anomalies.
As with the previous case, the resulting anomaly is again symmetrically distributed about the center of the sphere. In this case, however, the prominent central anomaly is negative and is surrounded by two smaller positive anomalies.