What factors affect the thermosphere?
Currently a good model of the thermosphere is defined by the COSPAR International Standard Atmosphere of 1972, or CIRA 72. The variations that are considered when defining the CIRA 72 thermosphere at a particular position and time are: • Solar Cycle and Solar Disk Approximately every 11 years the solar activity varies, having a solar maximum and solar minimum. This is called the Solar Cycle. During solar maximum the number of sun spots is at its greatest and vice versa for solar minimum. One part of the Ultraviolet (UV) radiation from the sun that heats up the Earths atmosphere, varies in correspondence with the number of sun spots on the visible solar disk. Today the solar-terrestrial environment is being constantly observed and recorded, giving people interested in such matters the ability to analyse evolutions of the system. • Diurnal Variation This is the variation during one solar day of the atmosphere. As the Earth rotates under the sun, the atmosphere is subjected to varying amo
