The propagation of electromagnetic waves in conducting, dielectric, and plasma media is traditionally treated in separate theoretical frameworks — Drude theory of metals, Lorentz oscillator theory of dielectrics, and Appleton–Hartree theory of ionospheric plasmas. This separation, while pedagogically convenient, obscures the underlying unity of the wave-propagation problem in linear isotropic media. The present work develops a single computational framework, based on the complex-permittivity form of Maxwell's equations, that treats all three classes of media on equal footing. We compute the complex refractive index ñ (ω) = n (ω) + i k (ω), penetration depth δ (ω), phase velocity v_φ (ω), and group velocity vg (ω) for representative media — copper (Drude), fused silica (single-oscillator Lorentz), and the daytime F2 ionospheric layer (cold collisional plasma) — across six decades of frequency from 10⁶ Hz to 10¹² Hz. Headline numerical results include a skin depth of 0. 79 μm for copper at 10 GHz, an F2 plasma cutoff at 8. 98 MHz, and an evanescent decay length of approximately 5 m for waves at 3 MHz in the daytime F2 plasma. A regime map summarizing the propagation behaviour of each medium across the full frequency range is presented as the central original contribution. All numerical results are validated against limiting-case analytical formulas. Limitations of single-oscillator fits are discussed and an extension toward polarised media via the formalism of Rasulov is outlined.
Feruzakhon et al. (Mon,) studied this question.
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