Wave impedance from atmospheric noise near 2 kHz

Atmospheric radio-noise measurements near the upper end of the e.l.f. band often indicate absorption and interference effects which are not present over most of the e.l.f. and v.l.f. bands. One such phenomenon is the sharp peaking of the magnitude of the ratio of vertical E to horizontal H, i.e. of the wave impedance characterising propagation in the earth-ionosphere waveguide. This paper gives a brief qualitative description of this phenomenon, and shows that its basic features may be attributed to interference between two waveguide modes. In addition, the possibility of using swept-frequency impedance measurements to precisely locate isolated thunderstorms is discussed.