The Navajo are the second largest tribe in the U.S. and they have the largest reservation stretching across Colorado, Utah, New Mexico and Arizona with over 25,000 square miles. They were also among the largest group of Indians to migrate to Los Angeles in the 1950s and 60s.
The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth, stretching from a height of about 50 km (31 mi) to more than 1,000 km (620 mi).
These extreme temperatures are caused by the absorption of the sun's shortwave ultraviolet radiation. This radiation penetrates the upper atmosphere, stripping atoms of their electrons and giving them a positive charge. Electrically charged atoms build up to form a series of layers within the thermosphere. These charged layers are often referred to as the ionosphere, which deflects some radio signals. Before the modern use of satellites, this deflection by the ionosphere was essential for long distance radio communication.