Overview of the temperature response in the mesosphere and lower thermosphere to solar activity

The natural variability in the terrestrial mesosphere needs to be known to correctly quantify global change. The response of the thermal structure to solar activity variations is an important factor. Some of the earlier studies highly overestimated the mesospheric solar response. Modeling of the mesospheric temperature response to solar activity has evolved in recent years, and measurement techniques as well as the amount of data have improved. Recent investigations revealed much smaller solar signatures and in some cases revealed no significant solar signal at all. However, not much effort has been made to synthesize the results available so far. This article presents an overview of the energy budget of the mesosphere and lower thermosphere and an up-to-date status of solar response in temperature structure based on recently available observational data. An objective evaluation of the data sets is attempted, and important factors of uncertainty are discussed.