Observations

Early on October 6, 1997, a horizontally-extensive region of thunderstorm activity was producing frequent -CG activity over Mexico. Significant +CG activity was noted at $\sim$02 UT and persisted for several hours until $\sim$06 UT. Initially, the +CG activity was at a range of $\sim$650 km, but the range increased to $\sim$900 km by 05 UT. The first high speed video trigger of a sprite event was obtained at 02:20 UT while the last was obtained at 05:55 UT. The high speed video camera was initially operated at 2000 frames/second. The frame rate was increased to 3000 frames/second prior to a 04:52 UT trigger and was further increased to 4000 frames/second prior to a 05:11 UT trigger.

A total of 16 sprite clusters, some less than a second apart, were sucessfully captured by the high speed video camera on October 6. Of the 16, 10 were obtained at 2000 frames/second, 4 were at 3000 frames/second, and 2 were at 4000 frames/second.

Normal-speed low-light-level video recordings began at 02:23:40 UT. Unfortunately, the VHS tape on which the recordings were made reached its end at 03:15:45 UT and this was not noticed until over an hour later. During this time period, the orientation of the high speed video camera could not be determined (see Appendix B.3). At 04:25:25 UT, normal-speed operations were continued and persisted throughout the remaining time period of high-speed video recordings.

The sferic data acquisition system started recording at 02:25:04 UT and continued recording for the duration of the observations. The 3-channel sferic data had the same composition as was used on October 7 (see Section 5.2.2). The trigger lengths were somewhat shorter with a pre-trigger of 2 ms and a post-trigger of 8 ms.