List of Figures

• 1.1. Important frequencies in the lower ionosphere
• 2.1. Electric field thresholds for air breakdown mechanisms
• 2.2. Ionospheric absorption
• 2.3. The first observed elve
• 2.4. Model ionization and dissociative attachment rates
• . Cross section of electric field and ${\rm N}_2(1{\rm P})$ optical emissions for EMP
• . Cross section of electric field and ${\rm N}_2(1{\rm P})$ optical emissions for QE
• 2.7. Model cross sections of ionization enhancement due to elves (EMP case) and the diffuse portion of sprites (QE case) 2 ms after the lightning stroke
• 2.8. Effect of multiple lightning strokes on ionization in elves
• 2.9. Multiple-stroke ionization changes area-averaged over $r<150$ km
• . Multiple-stroke ${\rm N}_2(1{\rm P})$ emissions area-averaged over $r<150$ km
• 3.1. Factors affecting intensity and timing of Rayleigh-scattered lightning flashes
• 3.2. Predicted photometric signatures of a Rayleigh-scattered lightning flash
• 3.3. Flash onset delay variation with viewing azimuth
• 3.4. Atmospheric transmission calculated with MODTRAN3
• 3.5. General geometry of a photometer and extended source
• 3.6. Factors affecting the photometric response to the ${\ensuremath{{\rm N}_2(1{\rm P})}}$ and ${\ensuremath{{\rm N}_2(2{\rm P})}}$ optical bands
• 3.7. Overview of the Fly's Eye photometer array
• 3.8. A single photometer of the Fly's Eye array
• 3.9. The Fly's Eye deployed at Langmuir Laboratory
• 3.10. Parallax in pointing calibrations
• 3.11. Calibrated photometer fields-of-view in 1998
• 3.12. Cross-section of the Fly's Eye photometer responses
• 3.13. CCD exposure timing for a frame-mode camera
• 3.14. Pointing determination using star fields
• 4.1. Geometry for photometric observations of elves at 500 to 900 km range
• 4.2. Modeled view of elves from the ground
• 4.3. Integrated model view of elves from the ground
• 4.4. Video image showing a sprite and elve
• 4.5. Temporal resolution of sprites and elves
• 4.6. Predicted and observed photometric signatures of elves
• 4.7. Photometric distinction between elves and lightning
• 4.8. Detection of blue emissions in an exceptionally bright elve
• 4.9. Bright elve viewed from an aircraft
• 4.10. Correlation between elves and lightning polarity
• 4.11. Theoretical and observed correlation between peak brightness and causative lightning intensity
• 4.12. Correlation between VLF intensity and NLDN reported peak current
• 4.13. Location of luminosity in elves
• 4.14. Horizontal extents of optical emissions in 38 elves from one mesoscale convective system
• 4.15. Predicted optical ratio of blue to red photometer signals as a function of electric field
• . Sensitivity of the Fly's Eye to ${\rm N}_2(1{\rm P})$ and ${\rm N}_2(2{\rm P})$ as a function of viewing elevation angle
• 5.1. Misinterpreted diffuse glow in video observations
• 5.2. Modeled and observed diffuse flash at 05:00:04.716 UT
• 5.3. Sprite halo following lightning at 04:45:48.962 UT
• 5.4. Sprite halo following lightning at 04:52:11.981 UT
• 5.5. Comparison of two sprite halos observed in normal and high speed video
• 5.6. Modeled temporal development of elves and sprite halos
• 5.7. Predicted photometric array signatures
• 5.8. Photometry and enhanced video images from the Fly's Eye for three events exhibiting sprite halos
• 5.9. Ambient electron density profiles for three values of $h'$, and the resulting modeled sprite halos
• 5.10. NLDN-recorded flashes from a nighttime MCS
• 5.11. Sprite associated with a large $-$CG return stroke and continuing current
• 5.12. Negative sprite at 06:11:14 UT
• 5.13. Negative sprite at 06:18:14 UT
• 5.14. Positive and negative streamers
• 5.15. Photometric features of a bright sprite
• 5.16. Slow sprite development and ULF currents
• 5.17. Sprite preceding cloud-to-ground lightning
• 5.18. Exponential decay times in sprites
• 5.19. Electric relaxation and attachment time scales as a function of altitude
• . Streamer velocities