A partially uniform knee (PUK) model is a combination of two two-dimensional telegraph equation (TDTE)-based techniques: the "knee" model, which addresses the problem of approximating the knee-like conductivity profile (on a semilogarithmic scale) of the Earth's ionosphere, and the global partially uniform day-night model, which allows a convenient treatment of the day-night asymmetry. Incorporation of the "knee" conductivity profile allows to overcome the shortcoming of the two-exponential technique, widely used in extremely low frequency (ELF) work, too flat frequency dependence of quality factor in the Schumann resonance (SR) range (5-40 Hz). The PUK model predictions for Schumann resonance parameters reasonably represent observations in the SR frequency range. Propagation parameters for other planets were calculated on the basis of existing ionospheric models of the planets. To allow the approximation of structured conductivity profiles of Venus and Mars, the "knee" model was upgraded to a double-"knee" by inserting an additional "knee" to the profile. In general, this technique allows to approximate very structured profiles by adding as many "knees" as necessary. Calculations show that the detection of Schumann resonances on Venus, Mars, and Titan is possible, though low-quality factors on Mars and Titan imply that pronounced peaks are not to be presumed on these planets.
- Schumann resonance