The region around the Sun including the photosphere, chromosphere, transition region, and corona. The temperature of the solar atmosphere varies with height, at first decreasing to the temperature minimum region and then increasing rapidly through the transition region and into the corona. The cause of the temperature rise is still uncertain, but possible mechanisms include the dissipation of sound waves (in the low chromosphere) and magnetohydrodynamic waves (in the rest of the chromosphere and corona), or heating following magnetic reconnection.