The ionosphere is a region of the space environment near Earth (geospace). It is located between approximately 60 and 1,000 km altitude. It is characterized by a relatively high density of free ions and electrons created, in most part, by solar photoionization.
The study of the ionosphere is motivated by a better understanding of complex physical processes that relate its behavior to activity in the sun and in the lower atmosphere. The study of the ionosphere is also motivated by its impact on the propagation of radio signals used for communication, navigation and remote sensing.
The video below created by NASA provides a brief, illustrative overview of the Earth’s ionosphere.
Ionospheric scintillation refers to fluctuations in the amplitude and/or phase of radio signals that propagated through the ionosphere. Scintillation is caused by perturbations in the ionospheric electron density (ionospheric irregularities) created by different processes. Therefore, measuring scintillation can help us better understand the conditions under which ionospheric irregularities can occur and their impact on radio signals.
Scintillation is commonly observed using signals transmitted by satellites orbiting above the ionospheric peak density and measured by receivers on the ground. Signals transmitted by Global Navigation Satellite Systems (GNSS) satellites such as GPS have been used by commercial scintillation monitors to measure scintillation.
In addition to scintillation, the background ionospheric electron density also causes delays in the radio signals. The delay is frequency-dependent with signals with higher frequencies being less affected by the ionospheric delay. GNSS satellites often transmit signals at multiple frequencies. Scintillation monitors capable of multi-frequency measurements can use differential delays to infer the total electron content (TEC) along the signal path between the satellite and monitor.
While ScintPi monitors cannot (and were not intended to) fully replace commercial scintillation and TEC monitors, they provide an affordable alternative for different educational and research initiatives.