Electromagnetic fields that are observed on the Earth with the worldwide network of magnetic observatories as well as regional means when surveying the Earth's interior are conventionally considered to be force and one-mode fields.
For the numerical modeling of electromagnetic fields observed on the Earth, a force component of Maxwell's equation is commonly used. This is because of its low-frequency oscillations. However for the numerical modeling of the major geomagnetic field (MGF), the potential of a force modification (mode) of a magnetic field in the air is employed.
A somewhat different situation exists in the theory of the MGF generation, where along with a force mode of the electromagnetic field its non-force part, which is called a Toroidal magnetic and Poloidal electric field, is used. This theory of the MGF generation as opposed to the other was called a theory of dynamic excitation of the MGF. Its main feature is the following: a non-force mode is not to appear in the Earth's atmosphere due to its strong tension (200-500 Hs) in the Earth's interior that is necessary for the MGF generation. The author shows that this is not so. A non-force electromagnetic field (a Toroidal magnetic and a Poloidal electric fields) is measured in the Earth's atmosphere along with a force component when the electromagnetic field tension is immediately fixed with an instrument. A magnetic field is measured with a magnetometer, an electric field – with an electrometer. Thus, a non-force electromagnetic field is an insurmountable obstacle in interpreting observations with a one-mode scheme.