Читать книгу Space Physics and Aeronomy, Ionosphere Dynamics and Applications - Группа авторов - Страница 15

The paradigm for coupling between the magnetosphere and ionosphere was established in a series of seminal papers in which connection of the Earth’s magnetic field to the interplanetary magnetic field (IMF) was postulated to drive ionospheric convection (Axford & Hines, 1961; Dungey, 1961; Axford, 1969). In this view, based on magnetohydrodynamic (MHD) fluid theory, the solar wind connects to the Earth’s magnetosphere, allowing solar wind momentum to be transferred across the boundary of the magnetosphere to set into motion magnetospheric plasma. Given the Earth’s magnetic field, B, motion of charged particles, V, is possible only if an electric field, E is generated where E = ‐ V x B.

This paradigm explained magnetic activity in which energy enters the high‐latitude ionosphere and is manifest as auroral brightening. Supporting this paradigm were the discovery of energetic particle precipitation in the auroral zones (Frank & Ackerson, 1971), and persistent field‐aligned currents (FACs) in the same latitude range (Zmuda et al., 1970). These discoveries contributed to widespread acceptance that (1) MHD reconnection is the dominant mechanism through which solar wind energy enters the ionosphere‐thermosphere (IT) system; (2) energy input and dissipation is highly localized in the auroral zones under active and quiet conditions. This hypothesis has been widely explored and challenged in recent years.

Ultimately the impact of energy deposition is heating of the ionosphere and thermosphere, commonly referred to as Joule heating. The transition from energy input to Joule heating involves the conductivity of the medium. Limitations on the length of this chapter preclude a full summary of Joule heat and conductivity, both complex topics in themselves, but brief descriptions of the physical processes are included for completeness.