For 10 points, name this geological phenomenon that, according to the dynamo theory, is caused by flow in the Earth's core.
One idea posited to limit potential explanations of this feature notes that, because of its strong axisymmetric component, it cannot have been created by a steady MHD flow. The strength of the most powerful interactions undergone by this entity are quantified in the so-called K index; those same interactions cause the South Atlantic Anomaly, which is of great concern to the space program. The aforementioned Cowling's theorem is one wrinkle in the standard theory of this object. Closed banana orbits within this approximate dipole give rise to the Van Allen belts. For 10 points, name this geological phenomenon that, according to the dynamo theory, is caused by flow in the Earth's core.
One idea posited to limit potential explanations of this feature notes that, because of its strong axisymmetric component, it cannot have been created by a steady MHD flow.
the Earth's {magnetic field} [accept {clear}-{knowledge} equivalents; accept {planetary magnetic fields} or {lunar magnetic fields} before “{K index}”; prompt on {B} or {M}]