Electrical Activity During the 2006 Mount St. Augustine Volcanic Eruptions
R. J. Thomas,1*
P. R. Krehbiel,1
W. Rison,1
H. E. Edens,1
G. D. Aulich,1
W. P. Winn,1
S. R. McNutt,2
G. Tytgat,2
E. Clark2
By using a combination of radio frequency time-of-arrival and
interferometer measurements, we observed a sequence of lightning
and electrical activity during one of Mount St. Augustine's
eruptions. The observations indicate that the electrical activity
had two modes or phases. First, there was an explosive phase
in which the ejecta from the explosion appeared to be highly
charged upon exiting the volcano, resulting in numerous apparently
disorganized discharges and some simple lightning. The net charge
exiting the volcano appears to have been positive. The second
phase, which followed the most energetic explosion, produced
conventional-type discharges that occurred within plume. Although
the plume cloud was undoubtedly charged as a result of the explosion
itself, the fact that the lightning onset was delayed and continued
after and well downwind of the eruption indicates that in situ
charging of some kind was occurring, presumably similar in some
respects to that which occurs in normal thunderstorms.
2 Alaska Volcano Observatory, University of Alaska, Fairbanks, AK 99775, USA.
* To whom correspondence should be addressed. E-mail: thomas{at}nmt.edu
