Sprites in low‐frequency radio noise

Abstract

Low‐frequency radio noise is the electromagnetic background radiation which is compared here to the luminosity of 39 sprites recorded with a low‐light video camera. It is found that the sprite luminosities coincide with ∼10–30 ms long sudden enhancements of the electromagnetic background radiation ∼6–8 μV m−1Hz−1/2(∼6–9 dB) with a relative maximum near ∼125 kHz as measured with a wideband (∼1–400 kHz) digital radio receiver. The sprites cluster in 10 groups of 2–5 consecutive sprites which are paralleled by up to ∼1 s long slowly varying enhancements of the electromagnetic background radiation ∼4–5 μV m−1Hz−1/2(∼2–4 dB). The observed electric field strengths place an upper bound on the low‐frequency radiation from the electron multiplication associated with the exponential growth and branching sprite streamers predicted by Qin et al. [2012a]. This upper bound corresponds to a maximum of ∼300–5000 sprite streamers at ∼40 km height above thunderclouds. Some part of the observed electromagnetic background radiation might result from the superposition of low‐frequency radiation emanating from the quick succession of numerous horizontal lightning strokes and/or stepped leaders inside thunderclouds which would constitute a fundamentally novel quasi‐static discharge process inside thunderclouds radiating slowly varying low frequency radio noise.

An unusual sequence of sprites followed by a secondary TLE: An analysis of ELF radio measurements and optical observations

“…However, the vertical component is the key parameter in the initiation of sprites [ Asano et al ., ]. Some recent theories suggest that a large charge moment change is a necessary but not sufficient condition for sprite initiation, and mesospheric irregularities might be a necessary condition for the initiation of sprite streamers [ Liu et al ., ; Kosar et al ., ; Qin et al ., ], and that the sprite streamers can produce low‐frequency electromagnetic radiation [ Qin et al ., ; Füllekrug et al ., ].…”

Time and space correlation between sprites and their parent lightning flashes for a thunderstorm observed during the HyMeX campaign

“…The sprite discharge can cover an altitude range from 40 to 90 km [ Sentman and Wescott , ; McHarg et al ., ] and appear as various vertically structured shapes, individual or multiple column or/and carrot‐shaped luminous elements [ Neubert et al ., ; van der Velde et al ., ]. Sprites can also horizontally extend over several tens of kilometers in the form of sprite clusters [ Sentman et al ., ; Füllekrug et al ., ; Soula et al ., ] and even over more than 100 km in the form of sequential luminous emissions that are called “dancing sprites” [ Winckler et al ., ; Füllekrug et al ., ].…”

Array analysis of electromagnetic radiation from radio transmitters for submarine communication

“…On the other hand, recent electromagnetic radiation measurements during sprite occurrences, which are located only ∼80 km away from a radio receiver, show a rapid succession of numerous broadband pulses with pausing time intervals ∼50–100 μs [ Füllekrug et al , ], similar to the pulse sequences observed during the initiation of lightning discharges [e.g., Kolmasova et al , ; Gurevich et al , ; Stolzenburg et al , , and references therein]. In fact, many sprites are associated with such pulse sequences, which blend into electromagnetic noise at large distances from the sprite [ Füllekrug et al , ]. Yet the underlying wave number vectors required for a more detailed array analysis to locate sprites are not very well known.…”