The thermosphere or ionosphere is the layer of the Earth's atmosphere that is located just above the mesosphere, and below the exosphere, the last layer of the atmosphere.
It is also called the ionosphere because ultraviolet rays cause photoionization of molecules in this layer, forming ions.
The name thermosphere comes from the Greek word thermos, which means heat. This name was chosen because this layer of the atmosphere has very high temperatures, because it absorbs large amounts of solar radiation. At some points, it can reach up to 2,000ºC in temperature.
The thermosphere ranges from 95 km high to approximately 600 km. Despite being part of the Earth's atmosphere, its density is so low that much of it belongs to what we usually call outer space.
Main characteristics of the thermosphere
The thermosphere is one of the five layers of the Earth's atmosphere, the other four being the troposphere, the stratosphere, the mesosphere, and the exosphere. It is the penultimate, just before the exosphere, and within its limits begins what we know as outer space.
Temperature
Despite the fact that the thermosphere maintains a very high temperature at all times, this temperature varies with the solar cycle.
Like the Earth's surface, the thermosphere is warmer during the day than it is at night; however, the variations can be several hundred degrees.
This layer of the atmosphere stretches between the mesopause (the point where the mesosphere ends) and the thermopause (the point in space where the thermosphere ends and the exosphere begins).
Elements
Despite not having a great density in air, the thermosphere is made up of relatively heavy elements: mainly helium, nitrogen and oxygen.
However, the air is so thin that it is often considered outer space. In fact, the International Space Station orbits the Earth within this layer of the atmosphere.
Features
This layer of the atmosphere is responsible for protecting us to a great extent from the sun's ultraviolet rays. Without it, life on Earth would be impossible.
Due to the ionization of its elements by the action of our star, the northern lights are produced in the thermosphere.
How is it formed?
These northern lights are produced when subatomic particles from space (especially protons and electrons) collide with different particles and molecules in the thermosphere.
These collisions produce discharges of energy that emit light, generating the phenomenon that can be seen near the Earth's poles.
Despite the fact that the thermosphere is the largest layer in the entire atmosphere, due to its low density, it is estimated that approximately 99% of all the air on Earth is below it.
Like Earth's oceans, the atmosphere has tides and "swell." These phenomena help move large amounts of energy through the different layers of the atmosphere; and they are especially strong in the thermosphere.
Due to the charge of the ions in this layer of the atmosphere, the gases found in it form powerful electric currents that move at high speeds inside it.
References
- "Thermosphere" in: Wikipedia. Retrieved on: December 22, 2017 from Wikipedia: en.wikipedia.org.
- "Thermosphere - Overview" in: Center for Science Education. Retrieved on: December 22, 2017 from Center for Science Education: scied.ucar.edu.
- "Thermosphere" in: NASA Science. Retrieved on: December 22, 2017 from NASA Science: spaceplace.nasa.gov.
- "Thermosphere Facts" in: Soft Schools. Retrieved on: December 22, 2017 from Soft Schools: softschools.com.
- "The Thermosphere" in: Windows to the Universe. Retrieved on: December 22, 2017 from Windows to the Universe: windows2universe.org.