What is the name of the hottest layer atmosphere?

The hottest layer of Earth's atmosphere is the thermosphere. In this layer, temperatures can reach up to 2,500 degrees Celsius (4,500 degrees Fahrenheit) or higher, primarily due to the absorption of high-energy solar radiation. The thermosphere is located above the mesosphere and below the exosphere, starting at about 85 kilometers (53 miles) above the Earth's surface.