Diameter-speed relation of sprite streamers

Abstract

Propagation and splitting of sprite streamers has been observed at high temporal and spatial resolution using two intensified high-speed CMOS cameras recording at 10 000 and 16 000 frames per second. Concurrent video recordings from a remote site provided data for triangulation allowing us to determine accurate altitude scales for the sprites. Diameters and speeds of the sprite streamers were measured from the high-speed images, and the diameters were scaled to the reduced diameters based on the triangulated locations. The sprite streamers with larger reduced diameter move faster than those with smaller diameter; the relation between the reduced diameter and speed is roughly linear. The reduced diameters at ≈65–70 km altitude are larger than streamer diameters measured at ground pressure in laboratory discharges indicating a deviation from the similarity law possibly due to the effects of the photoionization and an expansion of the streamer head along its propagation over a long distance. The reduced diameter and speed of the sprite streamers agree well with the diameter–velocity relation proposed by Naidis (2009 Phys. Rev. E 79 057401), and the peak electric field of the sprite streamers is estimated to be approximately 3–5 times the breakdown threshold field.

Plasma irregularities in the D-region ionosphere in association with sprite streamer initiation

“…On the basis of the altitude range of the entire image, which is calculated assuming the sprite streamer was directly above the causative lightning discharge, the vertical and horizontal size of the plasma irregularity are, respectively, B5 and B1 km. Alternatively, based on a 100-m typical diameter of sprite streamers documented in the existing literature 15 , the vertical and horizontal size of the plasma irregularity are, respectively, B2.5 and B0.5 km. These two estimates are roughly consistent with each other.…”

Sub-nanosecond delays of light emitted by streamer in atmospheric pressure air: Analysis of N2(C3Πu) and N2+(B2Σu+) emissions and fundamental streamer structure

“…Such a wave phenomenon results from the space charge left by electron avalanches [1,2]. Streamers are present in a large number of plasmas, whether operated in the laboratory [3][4][5][6][7][8], in industrial applications [9] or occurring in lightning and transient luminous events in upper atmosphere [10][11][12][13][14].…”

Positive streamers in air of varying density: experiments on the scaling of the excitation density

“…This happens for at least some of the streamers imaged at 400 mbar. This puzzle can be better answered experimentally if the focus artifact is resolved, for example by observing streamers in sprites [9,46,47], by using stereo-photographic imaging [48] to determine the 3D position of streamers and thereby their distance to the focal plane, or with guided streamers, where the trajectory of the streamer is determined by the setup [20,49].…”

“…The macroscopic parameters of streamers are described by simple scaling relations; the electric field in the streamer scales as the neutral density N, the diameter as 1 ⁄ N, and the densities of produced species (such as free electrons, ions, radicals and excited molecules) scale as N 2 [2][3][4][5]. Streamer diameters, velocities and inferred electric fields, measured in the laboratory at close to standard temperature and pressure were shown to scale with gas density to sprite streamers [6][7][8][9].…”

“…Streamers are a transient phenomenon, observed optically as the passage of a bright front, the streamer head, propagating at velocities between 10 5 and 10 7 m ⁄ s [9,19,26,41,42]. As the streamer propagates in the discharge gap, passing in the field of view of the camera, it illuminates several pixels in the image for less than 1 ns (and only a few microseconds in sprites), typically only a fraction of the camera exposure time.…”