Researchers simulate focusing effect of traveling ionospheric disturbances on solar dynamic spectra
Traveling ionospheric disturbances (TIDs) are among the Earth's ionosphere irregularities. They represent wave-like electron density structures propagating in the ionosphere. The motion of TIDs modulates the electron density distribution in space. It leads to a modification of plasma parameters, namely the refractive index, and affects the propagation of radio waves. In particular cases, the variations of plasma parameters strongly affect the lower-frequency electromagnetic waves that can result in focusing or amplification of the incident radiation (Meyer-Vernet et al. 1981). The focusing effect manifests itself in the form of peculiar spectral disturbances in intensity with specific morphology, so-called spectral caustics (SCs), occasionally appearing in dynamic spectra of solar radio instruments operating in the meter-decameter wavelength range.