Here's why:

* Thermosphere: This layer of Earth's atmosphere is characterized by extremely high temperatures, reaching thousands of degrees Fahrenheit. It's where the aurora takes place.

* Charged Particles: The aurora is caused by charged particles from the sun (solar wind) interacting with Earth's magnetic field. The thermosphere is where these particles are guided by the magnetic field lines.

* Excitation and Emission: When the charged particles collide with atoms in the thermosphere, they excite the atoms, causing them to release energy as light. This is the light we see as the aurora.