  The solar radiation focusing effect is related to the specific phenomenon of
propagation of the Sun-emitted HF and VHF waves through terrestrial ionosphere.
This natural effect is observed with ground-based radio instruments running
within 10-200 MHz range, as distinctive patterns - the Spectral Caustics (SCs)
- on the solar dynamic spectra. It has been suggested that SCs are associated
with medium-scale traveling ionospheric disturbances (MSTIDs). In this paper,
we present the first direct observations of SCs induced by MSTIDs, using solar
dynamic spectra with SCs obtained by different European radio telescopes on
January 8, 2014 and simultaneous two-dimensional detrended total electron
content (dTEC) maps over Europe. Spatial examination of dTEC maps as well as
precise timing analysis of the maps and the dynamic spectra have been
performed. First, we found several pairs of one-to-one (TID-SC)
correspondences. The study provides strong observational evidence supporting
the suggestion that MSTIDs are the cause of SCs.
