Radio waves are bounced off the ions and reflect waves back to earth. This generally helps radio communication. However, solar flares can increase the number of ions and can interfere with the transmission of some radio waves. Exosphere - the upper part of the thermosphere. It extends from about 550 km for thousands of kilometers.
Air is very thin here.
This is the area where satellites orbit the earth. More Information Magnetosphere - the area around the earth that extends beyond the atmosphere. The earth's magnetic field operates here. It begins at about 1000 km. It is made up of positively charged protons and negatively charged electrons.