In future, air navigation world-wide will be based on GNSS signals. The highest availability of service for positioning, velocity and time precision is then required. But in their travel from the satellite and to the receiver, GNSS signals cross the ionosphere: this perturbed atmospheric layer is responsible for the scintillation phenomenon that leads to abrupt signal intensity and phase changes at the receiver, and sometimes to a loss of signal track. These scintillations are more frequent at high and equatorial latitudes and are due to complex electromagnetic interactions between electrons, ions and the Earth magnetic field.