The region of the atmosphere known as the lower thermosphere (80 to 130 km in altitude) is more difficult to study than the regions at higher altitudes accessible to satellites and regions at lower altitudes accessible to balloons and aircraft. The high altitude energy inputs of the solar wind and solar ultraviolet propagate downward through it, and the lower altitude tidal and gravity wave energy inputs propagate upward through it, both depositing some of their energy on the way. To understand the coupling between the upper and lower atmosphere we must understand the structure and dynamics of the lower thermosphere and how it affects the energy propagating through it. High latitude studies are especially important in view of auroral energy sources. Two incoherent scatter radars in Alaska and Sweden have made extensive measurements over the last solar cycle that can be analyzed to yield the temperatures and winds and their variation with season, magnetic activity and solar cycle.
