What is Ionospheric Scintillation?
Ionospheric scintillation is a rapid fluctuation of radio-frequency signal phase and/or amplitude, generated as a signal passes through the ionosphere. Scintillation occurs when a radio frequency signal in the form of a plane wave traverses a region of small scale irregularities in electron density. The irregularities cause small-scale fluctuations in refractive index and subsequent differential diffraction (scattering) of the plane wave producing phase variations along the phase front of the signal. As the signal propagation continues after passing through the region of irregularities, phase and amplitude scintillation develops through interference of multiple scattered signals.
When and where does Ionospheric Scintillation occur?
Ionospheric scintillation is a well-known phenomenon that has been studied extensively in the past yet it remains a difficult phenomenon to predict or model on a large scale. Scintillation is caused by small-scale fluctuations in the refractive index of the ionospheric medium which in turn are the result of inhomogeneities. Inhomogeneities in the ionospheric medium are produced by a wide range of phenomena (eg plasma bubbles), and those responsible for scintillation occur predominantly in the F-layer of the ionosphere at altitudes between 200 and 1000km. The primary disturbance region, however, is typically in the F-region between 250 and 400km. E-layer irregularities such as sporadic-E and auroral E can also produce scintillation but their effect on L-band GPS signals is minimal.
Ionospheric scintillation is primarily an equatorial and high-latitude ionospheric phenomenon, although it can (and does) occur at lower intensity at all latitudes.
In terms of geographic (geomagnetic) distribution, ionospheric scintillation generally peaks in the sub-equatorial anomaly regions, located on average ~15° either side of the geomagnetic equator…