| ABSTRACT
Electrical
streamers are
one stage in a sequence of events that occur in the
development of sparks and lightning discharges. Sprites are very large
(km-scale) streamers that form in the upper atmosphere as a secondary
response to very large cloud-to-ground lightning discharges. Many
macroscopic aspects of streamers are still not well understood at the
microkinetic level, so the subject remains one of active investigation.
Recent high speed imaging of sprites at 10,000 fps — obtained in 2005
— provide
the most detailed space- and time-resolved description of streamer dynamics
that have been obtained to date, equivalent to imaging at about 1 billion
fps if scaled to atmospheric pressure. In this talk a preliminary model of
the highly coupled local chemical processes impulsively launched by a sprite
streamer is described. Results of the simulation show that the
attachment-recombination lifetime of electrons created by ionization in the
descending streamer head is long enough (~100s of ms at 70 km) to account
for the observed "reignition" of sprites from old sprite tendrils. The
principal ion remnants that survive longer than 1 second are
O2- and O-, and
NO+ and O4+. Subsequent interactions of the
negative ion remnants with
ambient CO2 and positive ion remnants with H2O
could constitute a
significant regional source of complex negative ions and hydrated positive
ions, respectively, within the upper atmosphere.
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