The altitude of sprites observed over South Africa

Abstract

Sprites are mesospheric optical emissions that are mostly produced by large, positive cloud-to-ground lightning discharges. Sprites appear in different morphologies such as carrot, jellyfish and column, and are typically in the altitude range of ~40–100 km above the Earth’s surface. Sprites are a subset of transient luminous events and they contribute to the global electric circuit. South Africa has large convective thunderstorms, which typically occur in the summer months of every year. Peak current, time and geographical position of lightning strokes were obtained from the South African Weather Service. Sprite observations were recorded in South Africa for the first time on 11 January 2016 from Sutherland in the Northern Cape using a night-vision television camera from the South African National Space Agency’s Optical Space Research laboratory. We report the first estimates of the top altitude, and the altitude of maximum brightness, of 48 sprites over South Africa. We found that the average top altitude and the altitude of maximum brightness of sprites are approximately 84.3 km and 69 km, respectively, which is consistent with estimates made elsewhere. We also found a moderately high positive and a weak positive correlation between the top altitude and the altitude of maximum brightness, respectively, of sprites and the lightning stroke charge moment change.

3D triangulation of Transient Luminous Events over Africa

“…Figure 1 respectively. This technique is described in detail by Mashao et al (2021). After the stars 5 fitting, we used the cosine and sine rule of spherical trigonometry to obtain simultaneous solutions for the angle subtended on the great circle (A) and slant distance to TLEs (r), as presented in Eq.…”

“…The TLEs' altitude difference between monostatic and triangulated estimates ranged from 1 to 2 km. For the monostatic method, the TLE altitude estimates assumed that TLEs occurred above the causal lightning stroke (Mashao et al, 2021). The uncertainty in TLE altitude determined from the angular resolution of camera varied from ±0.33 to 0.47 km.…”

“…dancing sprites. Most sprites altitude measurements have been done with the assumption that sprites are initiated over their parent lightning strokes, and sprites have been found to occur at an altitude ranging from about 45 to 95 km (Füllekrug et al, 2019;Li et al,2012;Mashao et al, 2021;McHarg et al, 2007;Ren et al, 2021;al., 1995;Stenbaek-Nielsen et al, 2010;Soula et al, 2015;Wescott et al, 1998;Wescott et al, 2001), spanning from about 50 to 90 km (Sentman et al, 1995), 48 to 88 km (Wang et al, 2019) and up to 96 km (Stenbaek-Nielsen et al, 2010). Wescott et al (1998) reported that the column sprites' top altitude ranged from 81.3 to 88.9 km.…”

Catalog of 525 sprites observed over Japan from September 2016 to March 2021

“…The analog output from the camera connects to an analog video capture device (Buffalo PC-SDVD/U2G), which captures frames at approximately 30 fps. The captured frames are processed on a PC by the software UFOCaptureV2 1 [32] , [50] in real-time. When the UFOCaptureV2 identifies a possible TLE by examining the difference between a previous frame and a current frame, the software records frames around the trigger time for three seconds (one second before the trigger time and two seconds after the trigger time) on the PC.…”

Estimating the electron energy and the strength of the electric field within sprites using ground-based optical data observed over South African storms

“…The instruments consist of two optical cameras; a WATEC 910Hx and an iXon Andor EMCCD camera. The WATEC 910Hx is a quasi-linear, low-light monochromatic Charge Coupled Device (CCD) that has a threshold illumination of 5.1X10 − 6 Lux and a 0.5-inch interline image sensor (Astroshop Eu, 2018), which is commonly used for sprites research around the world (Mashao et al, 2021;Nnadih et al, 2018;Soula et al, 2009;Yaniv et al, 2013). The camera was fitted with an 8.0 mm f/1.4 lens, which gave a field of view (FOV) of 43⁰ X 33⁰ and was operated at a frame rate of 25 Hz.…”