The processes producing the complex features of the magnetosphere must meet two requirements: sufficient energy must be available, and particles must somehow be accelerated to observed energies. As for the supply of energy, it was estimated [Axford, 1964; Stern, 1984] that about 1-2% of the solar wind energy impinging on the magnetopause cross-section is tapped by internal processes of the magnetosphere.
In the neutral atmosphere of the Earth, energy is usually transmitted by two mechanisms: by large-scale circulating flows which convect heat from the ground upwards, and by radiation which takes a more direct path. The magnetosphere, too, may transmit energy both by convective flows and by a more direct route, involving field-aligned currents.
In an ideal magnetized plasma, a steady bulk flow with velocity v requires the existence of an electric field E, satisfying the "ideal magnetohydrodynamic (MHD) condition" [e.g. Walen, 1946; Alfven, 1950]
E = – v × B (1)
Conversely, an electric field E impressed on a magnetospheric plasma produces a bulk flow satisfying (1). It is a property of (1) that "particles move with field lines", i.e. any group of ions or electrons sharing a field line at one time continues doing so ever after, and a "moving field line" in what follows will mean a moving string of plasma particles, threaded by a common field line. If dB/dt = 0, the magnetic configuration is fixed and on any "moving" line, the plasma population along its entire length migrates to an adjoining line: thus field lines can (for instance) transmit bulk motions from distant regions to their ionospheric ends. In inductive electric fields with dB/dt not zero, field line sharing also holds [Newcomb, 1958; Stern, 1966] but bulk motion is not necessarily transmitted along field lines [Stern, 1990, Figure 7].
The existence of the Chapman-Ferraro cavity (see BH-1) and hence of the magnetopause may be viewed as another consequence of field line sharing: as long as such sharing is rigorously enforced, there exists no way for interplanetary plasma, threaded (presumably) by fields of solar origin, to mix with plasmas of the Earth's field. For related reasons, as long as all terrestrial field lines are confined to the cavity's interior ("closed magnetosphere"), it is also difficult for energy, momentum and electric currents to enter the cavity from the outside. In the early days many scientists in fact believed that magnetospheric field lines were in this way completely confined inside the cavity. The alternative view of an "open" magnetosphere developed gradually and is discussed in sections 7 and 8.
Gold [1959, p. 1220] noted that the large scale flow of magnetospheric plasma (a type of which he was studying) "is quite analogous to thermal convection" and that led to the term "convection" used by Axford and Hines  to describe large-scale circulation inside the magnetosphere, caused by the solar wind. The theory of Alfven  (see BH-1, also Cowling  and Stern, ), although not consistently formulated, may also be viewed as a theory of magnetospheric convection. Contemporary theories began with Axford and Hines [1961, also Hines, 1974, p. 3, 933; Axford, 1962, 1964, 1994; Hines, 1964, 1986] and with the work of Dungey  described further below. Axford and Hines proposed a convective circulation to explain an observed pattern of auroral motions [Davis, 1962, 1971] in which plasma seemed to circulate in the polar cap.