  Drift-pair bursts are an unusual type of solar low-frequency radio emission,
which appear in the dynamic spectra as two parallel drifting bright stripes
separated in time. Recent imaging spectroscopy observations allowed for the
quantitative characterization of the drifting pairs in terms of source size,
position, and evolution. Here, the drift-pair parameters are qualitatively
analyzed and compared with the newly-developed Monte Carlo ray-tracing
technique simulating radio-wave propagation in the inhomogeneous anisotropic
turbulent solar corona. The results suggest that the drift-pair bursts can be
formed due to a combination of the refraction and scattering processes, with
the trailing component being the result of turbulent reflection (turbulent
radio echo). The formation of drift-pair bursts requires an anisotropic
scattering with the level of plasma density fluctuations comparable to that in
type III bursts, but with a stronger anisotropy at the inner turbulence scale.
The anisotropic radio-wave scattering model can quantitatively reproduce the
key properties of drift-pair bursts: the apparent source size and its increase
with time at a given frequency, the parallel motion of the source centroid
positions, and the delay between the burst components. The trailing component
is found to be virtually co-spatial and following the main component. The
simulations suggest that the drift-pair bursts are likely to be observed closer
to the disk center and below 100 MHz due to the effects of free-free absorption
and scattering. The exciter of drift-pairs is consistent with propagating
packets of whistlers, allowing for a fascinating way to diagnose the plasma
turbulence and the radio emission mechanism.
