Hydromagnetic waves and the lower ionosphere

Abstract Non-uniform two-dimensional hydromagnetic waves are assumed to be incident on an idealised lower ionosphere. The waves have a sinusoidal horizontal amplitude factor. The ionosphere and sea-level region is represented by a simple layered model. The ionospheric Pederson conductivity is made zero and the Earth's magnetic field vertical. Transmission and reflection are examined theoretically, and the following results are noted: (1) At sea-level, resonant peaks in amplitude occur at about the same periods as for incident plane waves; but the longest period peak is absent. (2) Polarisation at sea-level is linear. (3) Reflection from the lower ionosphere is imperfect. (4) A modified plane wave model is valid at short periods. (5) The thin ionosphere model is valid at long periods.