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Magnetosphere – ionosphere coupling in the auroral region
Magnetosphere–ionosphere (M–I) coupling is an outstanding example of interaction between
two widely different plasma regimes, hot and rarefied in the magnetosphere, cold and dense
in the ionosphere. In the auroral region, the M–I coupling is achieved, essentially, by a
superposition of quasi-stationary and time-dependent field-aligned currents (FACs), with the
time-dependent FACs carried typically by Alfven waves. In a simplified picture, energy and
momentum provided by generator regions in the magnetosphere (like, for example, those
discussed under Plasma sheet) are transferred via FACs to the resistive ionosphere. A key
element of the M–I coupling chain is the auroral acceleration region, a transient potential
structure located at 1–2 Earth radii altitude, where charged particles are energized by electric
fields parallel to the magnetic field. The aurora is the ultimate effect of this interaction chain,
which results from the collisions of the energetic electrons with the constituents of the neutral
atmosphere.
The M–I coupling work performed under ECSTRA addressed the low altitude end of the M--
I system, namely the auroral acceleration region and the electrodynamics of the auroral
ionosphere. This work materialized in three papers (Marghitu et al., 2009a, 2011a; Marghitu,
2012), three invited talks (Marghitu, 2009; Marghitu et al., 2010b, 2011b), several other talks
and posters (see Publications), as well as one invited seminar (Marghitu, 2011b). The
M–I coupling investigations performed under ECSTRA are closely related to topics
addressed in the framework of the projects ALEGRO, POLARIS, and M-ICAR.
Auroral acceleration region
Ionospheric electrodynamics
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