EVIDENCE OF IONIZATION:
BLUE SPRITES IMAGED AT YUCCA RIDGE
16 JULY 1995 and 24 JULY 1996


Blue Images Provide Clear Evidence of Ionization in Sprites (1996)


Upcoming Papers to be Published in the Journal of Atmospheric and Solar Terrestrial Physics in 1998 (Special Issue): 


TITLE:        Blue-Light Imagery and Photometry of Sprites

AUTHORS:      David M. Suszcynsky, Robert Roussel-Dupre, Los Alamos National Laboratory
              Walter A. Lyons, FMA Research, Inc.
              Russell A. Armstrong, Mission Research Corp.
              
ABSTRACT:     We have obtained blue (350-475 nm) video images and simultaneous high-time
              resolution narrow-band blue (415-435 nm) photometry of four sprite events.
              The brightest blue images show a sustained tendril geometry and a nearly
              constant intensity of emission over the entire vertical extent of the
              sprite (25 - 80 km).  Photometer light curves display an exponential decay
              with a 0.3 ms time constant, a FWHM of 0.1 - 1.0 ms, and are likely dominated
              by 427.8 nm emission.  The data is in support of the observations of 
              Armstrong, et al. (1996) and supports the contention that significant
              ionization occurs during sprite generation.

REFERENCE:    Armstrong, R.A., J.A. Shorter, W.A. Lyons, L.S. Jeong,  and W.A.M. Blumberg,
              (1995), Photometric Measurements in the SPRITES'95 Campaign: Evidence for 
              Nitrogen First Negative (4278A) Emission.  EOS Abstract, AGU Fall Meeting,
              San Francisco, December 1995.

July 16, 1995 RESULTS



This comparison of images and photometer traces obtained on 16 July 1995 was among the first data recorded showing that sprites exhibit a 427.8 nm emission, indicating initiation with an ionization pulse. This was a coincident 427.8 nm photometer observation of sprites (Armstrong) with Xybion video images (Lyons) when elve and tendril structure is detected. The 427.8 nm photometer trace clearly shows the initial and rebrightening ionization event which initiates the sprite optical emission. 


TITLE:        Photometric Measurements in the SPRITES'95 and '96 Campaigns: Nitrogen
              Second Positive (399.8 nm) and First Negative (427.8 nm) Emission.
              
AUTHORS:      R.A. Armstrong, J.A. Shorter, Mission Research Corporation
              M.J. Taylor, Utah State University
              D.M Suszcynsky, Los Alamos National Laboratory
              W.A. Lyons, FMA Research, Inc.
              L.S. Jeong, USAF Phillips Laboratory
              
ABSTRACT:     We have obtained blue photometric measurements of the N2 second positive 399.8
              nm and the N2 first negative 427.8 nm emission from sprites, elves and lightning,
              along with supporting video images.  The pulse width and intensity results for
              sprites are consistent with those of Suszcynsky, et al. (1997).  The red
              emission from sprites has been independently and unambiguously identified by
              Hampton, et al. (1996) and Mende, et al. (1995) as the nitrogen first positive band.  
              The source has been attributed to electron impact excitation from low energy 
              electrons (~1 eV) in the sprite.  The short pulse width of the 427.8 nm and 
              399.8 nm photometer time traces obtained in this investigation are likely not
              from the same source as the red emission.  The results reported here indicate
              an initial energetic ionizing event sufficient to ionize and excite 
              nitrogen followed by secondary electron processes which give rise to the dominant
              red emission.  The photometer results for elves is consistent with the EMP
              mechanism suggested by Inan, et al. (1996).  The photometer traces obtained 
              for lightning indicate emissions consistent with "continuing current" as the
              charge redistributes within the thunderstorm cloud.  We find that the ratio of
              the intensities of the 399.8 nm N2 (2P) emission to the 427.8 nm N2 (1N) emission
              can be used to discriminate among sprites, elves and lighning.
              
REFERENCES:   Hampton, D.L., Heavner, M.J., Wescott, E.M, and Sentman, D.D., 1996.  Optical
              Spectral Characteristics of Sprites, Geophys. Res. Lett., 23, 89-92.
              
              Inan, U.S., Barrington-Leigh, C, Hansen, S., Glukhov, V.S., Bell, T.F., and
              Rairden, R, 1997. Rapid lateral expansion of optical luminosity in lightning-
              induced ionospheric flashes referred to as "elves".  Geophys. Res. Lett., 24,
              583-586.
              
              Mende, S.B., Rairden, R.L., Swenson, G.R., and Lyons, W.A., 1995.  Sprite spectra:
              N2 first positive band identification.  Geophys. Res. Lett., 22, 2633-2636.
              
              Suszcynsky, D.D., Roussel-Dupre, R.A., Lyons, W.A., and Armstrong, R.A., 1997.
              Blue Light Imagery and Photometry of Sprites.  Journ. of Atmos. and Solar Terr.
              Phys. See above.

July 24, 1996 RESULTS