What perytons are not, and might be

Chirped radio pulses known as perytons are consistent with plasma propagation, but an astronomical origin has been excluded. This paper considers several physical processes as possible explanations. TE and TM waveguide modes have dispersion relations formally similar to those of plasmas, and emission at the plasma frequency of a plasma recombining by two-particle processes also produces a chirp δt ω^-2, but these hypotheses fail quantitatively. The chirp might be approximately fitted to three-body recombination, cyclotron radiation in exponentially decaying fields, or to the resonance of a distributed LC circuit whose component conductors move. Constraints are placed on these possible processes, but no specific source has been identified.