Abstract
Abstract. In this brief note we explore the role of the neutral atmosphere in magnetosphere–ionosphere coupling. We analyze momentum balance in the ion rest frame to form hypotheses regarding the role of neutral momentum in the lower ionosphere during geomagnetic storms. Neutral momentum that appears in the ion rest frame is likely the result of momentum imparted to ionospheric ions by solar wind flow and the resultant magnetospheric dynamics. The resulting ion-neutral collisions lead to the existence of an electric field. Horizontal electron flow balances the momentum supplied by this electric field. We suggest a possible role played by the neutral atmosphere in generating field-aligned currents due to local auroral heating. Our physical interpretation suggests that thermospheric neutral dynamics plays a complementary role to the high-latitude field-aligned currents and electric fields resulting from magnetospheric dynamics. Keywords. Ionosphere (ionosphere–magnetosphere interactions; polar ionosphere) – magnetospheric physics (magnetosphere–ionosphere interactions)
Highlights
Momentum transfer from the solar wind to the magnetosphere and ionosphere is a significant source of geospace dynamics, which is enhanced during periods of geomagnetic activity
We discuss a perspective on ionospheric electrodynamics that emphasizes the importance of ion-neutral velocity differences within the high-latitude ionosphere
To the extent that such velocity differences are not caused by currents originating with magnetospheric processes, this perspective de-emphasizes magnetospheric current systems as a primary causative factor in magnetosphere–ionosphere coupling
Summary
Momentum transfer from the solar wind to the magnetosphere and ionosphere is a significant source of geospace dynamics, which is enhanced during periods of geomagnetic activity. A number of consequences are known to occur, such as increased field-aligned currents (FACs) that flow between the ionosphere and magnetosphere, enhanced ionization due to precipitating particles, increased and enlarged high-latitude plasma convection, and neutral atmosphere heating (Kelley, 2009; Brekke, 2013). The complex physical processes that occur in the partially ionized, collisional plasma that resides in the lower ionosphere are often described using Ohm’s law (Song et al, 2001), which
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