Answer:
Chromosphere
Step-by-step explanation:
The Chromosphere is one of the important internal layers of the sun, which lies above the layer of Photosphere. The Chromosphere has a thickness of about 3 to 5 km having a very high temperature, ranging from about 5000 to 20,000°C. Due to this extreme temperature and continuous nuclear fusion process that takes place at the core of the sun, there forms the reddish colored layer, which is usually not visible but can be observed during the time of a total solar eclipse, by the use of an ultraviolet telescope.