Frontiers in the D-region physics

We review the contemporary level of the lower ionosphere study. The progress in ionosphere physics is based on the complex measurements as well as on the self-consistent 3D computer codes but this is not the case for the lower ionosphere. We point out the problems which are necessary for the solar-terrestrial links, transient electrooptical events in the middle atmosphere and even for the global climate community models. Special attention is paid to the problem of verification using satellite and ground-based evidence. The examples from VLF-LF monitoring prove the requirement of further study of the lower ionosphere processes.