This chapter is revised from a previously published book chapter [35]. The free electrons and ions in the Earth’s ionosphere make it electrically conducting. Currents flow that are connected with the magnetosphere above, and to a much weaker extent with the poorly conducting atmosphere below. One... Show moreThis chapter is revised from a previously published book chapter [35]. The free electrons and ions in the Earth’s ionosphere make it electrically conducting. Currents flow that are connected with the magnetosphere above, and to a much weaker extent with the poorly conducting atmosphere below. One of the important generators of the ionospheric current is the ionospheric wind dynamo, which operates as upper-atmospheric winds move the electrically conducting medium through the Earth’s magnetic field, creating an electromotive force that drives currents and causes electric polarization fields to develop. Other current generation mechanisms exist associated with the interaction of the solar wind with the magnetosphere [7], and, to a much less significant extent, with electrified clouds in the troposphere [43]. In the daytime ionosphere the largest currents flow between 90 km and 200 km; this general region is sometimes called the dynamo region. The currents and electric fields interact with the dynamics of the ionospheric plasma and neutral air in and above the dynamo region. We call the electrical phenomena and their interacting dynamical effects ionospheric electrodynamics. The historical development of the field has been described in [50, 6, 26, 4]. Show less
