Investigating Sprite Halo Optical Signatures and Associated Lightning Characteristics over South America

As part of the Sprites II balloon campaign conducted from Santa Maria, Brazil (29.4 S, 53.8 W) during the summer 2006 over 500 transient luminous events were imaged from two large thunderstorms located over north-eastern Argentina on February 22-23 and March 3- 4 2006. Ground-based measurements were made using an array of intensified CCD cameras arranged to view the low elevation sky over a broad angle to capture the TLE information from the extensive storm systems. This paper focuses on the optical characteristics of over 100 sprite halos and their associated polarity and charge moments as determined by an ELF-VLF lightning sensor also deployed at the Santa Maria research station. Recent satellite measurements of halos over land-sea interfaces suggest that they are mainly associated with negative cloud-to-ground discharges. The prime location of our coordinated measurements centered over the Pampas of South America has enabled us to quantify the polarity of the halos and to study their associated charge moments.