PHOTOMETRIC MEASUREMENTS IN THE SPRITES-95 AND SPRITES-96 CAMPAIGNS OF NITROGEN 2ND POSITIVE (399.8 NM) AND FIRST NEGATIVE (427.8 NM) EMISSIONS

We have obtained blue photometric measurements of the N-2 second posit ive 399.8 nm and the N-2(+) first negative 427.8 nm emission from spri tes, elves and lightning, along with supporting video images. The puls e width and intensity results for sprites are consistent with those of Suszcynsky et al. (1998). The red emission from sprites has been inde pendently and unambiguously identified by Hampton et al. (1996) and Me nde et al. (1995) as the nitrogen first positive band. The source has been attributed to electron impact excitation from low energy electron s(approximate to 1 eV) in the sprite. The short pulse width of the 427 .8 nm and 399.8 nm photometer rime traces obtained in this investigati on are probably not from the same source that produces the red emissio n. The results reported here indicate an initial energetic ionizing ev ent sufficient to ionize and excite nitrogen followed by secondary ele ctron processes which give rise to the dominant red emission. The phot ometer results for elves are consistent with the EMP mechanism suggest ed by Inan et al. (1996). The photometer traces obtained for lightning indicate emissions consistent with a 'continuing current' as the char ge redistributes within the thunderstorm cloud. We find that the ratio of the intensity of the 399.8 nm N-2(2P) emission to that of 427.8 nm N-2(+) (1N) emission can be used to discriminate among sprites, elves and lightning. (C) 1998 Elsevier Science Ltd. All rights reserved.