What Perytons Aren't, and Might Be
  Chirped radio pulses known as perytons are consistent with plasma propagation, but an astronomical origin has been excluded. 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 $\delta t \propto \omega^{-2}$, 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, but no specific source has been identified. 
J. I. Katz
astro-ph.HE physics.ins-det physics.plasm-ph