Gigantic jets between a thundercloud and the ionosphere

Abstract

Transient luminous events in the atmosphere, such as lighting-induced sprites and upwardly discharging blue jets, were discovered recently in the region between thunderclouds and the ionosphere. In the conventional picture, the main components of Earth's global electric circuit include thunderstorms, the conducting ionosphere, the downward fair-weather currents and the conducting Earth. Thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere, where the electric potential is hundreds of kilovolts higher than Earth's surface. It has not been clear, however, whether all the important components of the global circuit have even been identified. Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude approximately 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites.

A gigantic jet event observed over a thunderstorm in mainland China

“…Provided that all these information were known, the altitudes of the GJ in Figure 1(a) could be estimated by using method mentioned in Yang et al [14]. The estimated altitude of the bottom and top of the GJ on the image are about 52 and 89 km, respectively, consistent with results reported by other authors [17][18][19][20]. Although the north part was weaker than the south one, there was still some possibility that it produced the GJ.…”

“…Type-I GJs have similar characteristics as reported by Pasko et al [17] and Su et al [18]. Type-I GJs have three stages during its evolution, the leading jet (LJ), fully developed jet (FDJ) and trailing jet (TJ).…”

“…The lowest cloud top brightness temperature was 75°C in the sprite time period, a little lower than that of the previous studies [14,26]. Figure 3 [18], indicating convection in storm A at this time was very strong and in good agreement with previous studies [17,18]. In addition, results from Qingdao radio sounding data (the distance between the storm and Qingdao station was about 100 km, this is the nearest station we could found) show that the CAPE (Convective Available Potential Energy) value was 1294 J/kg at 20:00 on 12 August, and decreased to 363 J/kg at 08:00 on 13 August, indicating a lot of energy was consumed and the convection was also strong.…”

“…Although the north part was weaker than the south one, there was still some possibility that it produced the GJ. To clarify this question, similar calculations were made and results show that the bottom and top of the GJ on the image would be at 38 and 74 km, respectively, much lower than that of the known results in the literature [17][18][19][20]. This leads to a conclusion that GJ was produced by the south part of storm A.…”

“…This discharge event was not named as "gigantic jet" at that time but named by Pasko et al [17] as "electrical discharge from a thundercloud top to the lower ionosphere". Five similar discharges were recorded by Su et al [18] from Cheng Kung University over a thunderstorm near Luzon Island, and this kind of discharge was first named as "gigantic jet". Thereafter, Van der Velde et al [19], Cummer et al [20], and Chou et al [21] reported gigantic jet observations, re-spectively.…”