Solar Flare Effects on the Thermosphere and Ionosphere

Solar flares are sudden increased brightness from the Sun's active regions, mainly in soft X-rays (0.1–10 nm), and in extreme ultraviolet (10–121.6 nm). Solar flares often last for less than an hour, and their radiation takes only 8 minutes to arrive at Earth. Solar irradiance in these energetic short wavelengths ionizes the thermosphere and creates the ionosphere. Therefore, solar flares can have significant impacts on both the thermosphere and ionosphere. In this chapter, we use model simulations and observations to illustrate and understand solar flare effects in the thermosphere and ionosphere system, how flare characteristics affect flare responses in the thermosphere and ionosphere, the EUV late phases of solar flares, how the EUV late phases impact the thermosphere and ionosphere, and large-scale traveling atmospheric disturbances during concurrent solar flare and geomagnetic storm events.