What is the typical boundary height of the thermosphere?

The thermosphere is defined as the layer of the Earth’s atmosphere that is situated above the mesosphere and extends well into the upper reaches of the atmosphere. Its lower boundary begins at approximately 50 miles (80 kilometers) above sea level, which positions it directly above the mesosphere. The thermosphere itself can reach heights of several hundred miles, often cited as extending up to around 600 miles (1,000 kilometers) or more.

In this context, recognizing that the thermosphere is the atmospheric layer that follows the mesosphere is essential in understanding its boundary. When considering the height of the thermosphere, it is typically understood to be above the mesosphere, transcending the other options which suggest specific mile ranges that do not encompass the full extent of this layer's height. Therefore, identifying the thermosphere as the region situated above the mesosphere accurately reflects its placement within the atmospheric structure.