I found something interesting here, regarding Russian research into longitudinal electromagnetic waves, as opposed to the standard theories on transverse waves
As the practical substantiation of longitudinal EM waves existence, the author has created and tested the device for radiation and reception of longitudinal EM wave. The very first experiments have already shown the essential difference of these waves from transversal waves. However, let us adjourn the analysis of the experimental data for the next papers, as this expects to create at least the initial new model, which exceeds the limits of present paper. (This paragraph was written in 1990)."