For 10 points, name this uppermost part of the atmosphere, which contains many charged particles.
Its maximum usable frequency is calculated by dividing by its angle of attack. The open system space tether, once produced, will use energy from this region. Studied by the Alouette series of satellites, this region contains many unreachable propagation paths which can open up during Sporadic-E events. Very Low Frequency signals that hit prior to SIDs affect its D layer. It also contains the Kennelly-Heaviside layer and interacts with solar flares. For 10 points, name this uppermost part of the atmosphere, which contains many charged particles.
Its maximum usable frequency is calculated by dividing by its angle of attack.
ionosphere