Giant Sparks at Cosmological Distances?
  Millisecond duration bright radio pulses at 1.4-GHz with high dispersion
measures (DM) were reported by Lorimer et al., Keane et al., and Thornton et
al. Their all-sky rate is $\approx 10^4$/day above $\sim$1 Jy. Related events
are "Perytons" -- similar pulsed, dispersed sources, but most certainly local.
Suggested models of fast radio bursts (FRBs) can originate in the Earth's
atmosphere, in stellar coronae, in other galaxies, and even at cosmological
distances. Using physically motivated assumptions combined with observed
properties, we explore these models. In our analysis, we focus on the Lorimer
event: a 30 Jy, 5-ms duration burst with DM$=$ 375 cm$^{-3}$ pc, exhibiting a
steep frequency-dependent pulse width (the {\it Sparker}). To be complete, we
drop the assumption that high DMs are produced by plasma propagation and assume
that the source produces pulses with frequency-dependent arrival time ("chirped
signals"). Within this framework we explore a scenario in which Perytons, the
{\it Sparker}, and the FRBs are all atmospheric phenomenon occurring at
different heights. This model is {\it ad hoc} in that we cannot explain why
Perytons at higher altitudes show greater DMs or exhibit narrower pulses.
Nonetheless, we argue the {\it Sparker} may be a Peryton. We end with two
remarks. First, the detection of a single FRB by an interferometer with a
kilometer (or longer) baseline will prove that FRBs are of extra-terrestrial
origin. Second, we urge astronomers to pursue observations and understanding of
Perytons since they form (at least) a formidable foreground for the FRBs.
