Editing Thermosphere (section)

===Solar wind===
The second source of energy input into the thermosphere is [[solar wind]] energy which is transferred to the [[magnetosphere]] by mechanisms that are not well understood. One possible way to transfer energy is via a hydrodynamic dynamo process. Solar wind particles penetrate the polar regions of the magnetosphere where the [[geomagnetic field]] lines are essentially vertically directed. An electric field is generated, directed from dawn to dusk. Along the last closed geomagnetic field lines with their footpoints within the [[auroral]] zones, field-aligned electric currents can flow into the [[ionospheric dynamo region]] where they are closed by electric [[Pedersen current|Pedersen]] and [[Hall current]]s. [[Ohm]]ic losses of the Pedersen currents heat the lower thermosphere (see e.g., [[Magnetospheric electric convection field]]). Also, penetration of high energetic particles from the magnetosphere into the auroral regions enhance drastically the electric conductivity, further increasing the electric currents and thus [[Joule heating]]. During the quiet magnetospheric activity, the magnetosphere contributes perhaps by a quarter to the thermosphere's energy budget.<ref>Knipp, D.J., W.K. Tobiska, and B.A. Emery, Direct and indirect thermospheric heating source for solar cycles, Solar Phys., ''224'', 2506, 2004</ref> This is about 250&nbsp; K of the exospheric temperature in eq.(2). During the very large activity, however, this heat input can increase substantially, by a factor of four or more. That solar wind input occurs mainly in the auroral regions during both day and night.