The present paper reveals that the air contains electromagnetic energy of extremely low frequency, low amplitude as well as of a low phase speed. The energy is of great interest because of its impact on certain biological processes. It is created by the interaction of two well-known phenomena. The rotation of the earth generates 24 h periods currents in the magnetosphere, known as the Birkeland currents. The currents generate transverse electromagnetic waves (EM waves) propagating parallel to the geomagnetic field lines. Furthermore, the air and the earth crust contain electrons caused by the global electric circuit. The electric field vectors of the EM waves exert a force on these electrons, causing them to oscillate and thus generate currents of extremely low frequency both in the air and in the earth crust. A theoretical model of the system is presented and measurement techniques are described. Measurements have been performed during a six year period. The results of the performed measurements verified the theoretical model. Impact on biological processes is discussed.