Past exam of the year 2 of the earth sciences (geology) course of the University of Oxford / 2025 / Paper 3 / 2 / d / ii

At the magnetic equator, the inducing magnetic field and induced magnetic moment are horizontal. Let $x$ point along this field, approximately magnetic north, and $y$ across it. Directly over the car, the dipole field opposes the main field, producing a negative central total-field magnetic anomaly. A north–south traverse through the car givesa symmetric central low with positive shoulders. An east–west traverse through the car instead has $\Delta T(y)\propto -(y^2+h^2{)}^{-3/2}$, a single negative trough. The equatorial anomaly therefore needs a stated traverse orientation; there is no universal single equatorial line profile.