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Abstract We observed two Terrestrial Gamma‐ray Flashes (TGFs) in Uchinada, Japan associated with negative cloud‐to‐ground lightning strokes exactly 1 year apart on 18 December 2020 and 2021. The events were remarkable for their lateral distance from the associated strokes—each about 5 km away from the detector site. Not only was that lateral distance remarkable on its own for a ground based detection, but the low‐altitude profile of winter thunderstorms in Japan would suggest the detections occurred at unprecedented nadir angles—73.3° off axis for the 2020 event with the standard assumption of a vertically oriented TGF. Unsurprisingly, Monte Carlo simulations of the straightforward interpretation of these events yield fluences 2 orders of magnitude lower than observed data. We investigate a variety of ways to attempt to resolve the contradiction between expected and observed behavior. 

We present observations of X-rays from laboratory sparks created in the air at atmospheric pressure by applying an impulse voltage with long (250 µs) rise-time. X-ray production in 35 and 46 cm gaps for three different electrode configurations was studied. The results demonstrate, for the first time, the production of X-rays in gaps subjected to switching impulses. The low rate of rise of the voltage in switching impulses does not significantly reduce the production of X-rays. Additionally, the timing of the X-ray occurrence suggests the possibility that the mechanism of X-ray production by sparks is related to the collision of streamers of opposite polarity. 

Abstract Prior research into the conceptual underpinnings of the public's institutional trust in zoos and aquariums has suggested a range of ethical dimensions that set these types of cultural institutions apart from others in the museum sector. As the recognized holders, care‐takers, and nurturers of wild animals, zoos and aquariums are sustained at least in part by the public's perception that these activities are legitimate pursuits and essential to the long‐term conservation of the natural world. This paper builds on recent research that identified the ethical dimensions of trust in zoos and aquariums and assessed their distribution among the U.S. public by analyzing survey responses with respect to the importance of trust criteria. We hypothesized that distinct clusters of individuals, as defined by their response to trust criteria items, would emerge and that these clusters would prioritize different dimensions in their trust of zoos and aquariums. Usingk‐means clustering, we identified four relevant clusters of individuals on seven dimensions of institutional trust in zoos and aquariums. Based on these clusters, we suggest strategies for addressing what may be necessary for zoos and aquariums to claim authority as agents promoting conservation behaviors in society. 

Abstract In 2015, Bowers et al. (2018,https://doi.org/10.1029/2017JD027771) detected a terrestrial gamma ray flash (TGF) in Hurricane Patricia from an aircraft flying at 2.6 km through what they argued to be a beam of downward gamma radiation produced by the positron component of the TGF. This paper uses the energy spectrum for gamma rays produced by the positrons of a relativistic runaway electron avalanche as simulated by the REAM code, propagated through a model of the Earth's atmosphere in Geant4, to examine the feasibility of detecting a typical upward TGF through its reverse positron beam at various altitudes on the ground. We find that, with patience, modest‐sized scintillators on mountains as low as 1 km should be able to observe the same TGFs seen from spacecraft. 

Abstract This paper reports a study to understand the radio spectrum of thunderstorm narrow bipolar events (NBEs) or compact intracloud discharges, which are powerful sources of high‐frequency (HF) and very high frequency (VHF) electromagnetic radiation. The radio spectra from 10 kHz to about 100 MHz are obtained for three NBEs, including one caused by fast positive breakdown and two by fast negative breakdown. The results indicate that the two polarities of fast breakdown have similar spectra, with a relatively flat spectrum in the HF and VHF band. The ratio of energy spectral densities in the very low frequency and HF bands is (0.9–5) × 10⁵. We develop a statistical modeling approach to investigate if a system of streamers can explain the main features of fast breakdown. Assuming that the current moment peak and charge moment change of individual streamers vary in the ranges of 5–10 A‐m and 5–20 μC‐m, respectively, the modeling results indicate that a system of 10⁷–10⁸streamers can reproduce the current moment, charge transfer, and radio spectrum of fast breakdown. The rapid current variation on a time scale of nanoseconds required for fast breakdown to produce strong HF/VHF emissions is provided by exponentially accelerating and expanding streamers. Our study therefore supports the hypothesis that fast breakdown is a system of streamers. Finally, suggestions are given regarding future streamer simulations and NBE measurements in order to further develop our understanding of NBEs and lightning initiation. 

Abstract The production mechanism for terrestrial gamma ray flashes (TGFs) is not entirely understood, and details of the corresponding lightning activity and thunderstorm charge structure have yet to be fully characterized. Here we examine sub‐microsecond VHF (14–88 MHz) radio interferometer observations of a 247‐kA peak‐current EIP, or energetic in‐cloud pulse, a reliable radio signature of a subset of TGFs. The EIP consisted of three high‐amplitude sferic pulses lasting≃60μs in total, which peaked during the second (main) pulse. The EIP occurred during a normal‐polarity intracloud lightning flash that was highly unusual, in that the initial upward negative leader was particularly fast propagating and discharged a highly concentrated region of upper‐positive storm charge. The flash was initiated by a high‐power (46 kW) narrow bipolar event (NBE), and the EIP occurred about 3 ms later after≃3 km upward flash development. The EIP was preceded≃200μs by a fast6 × 10⁶m/s upward negative breakdown and immediately preceded and accompanied by repeated sequences of fast (10⁷–10⁸m/s) downward then upward streamer events each lasting 10 to 20μs, which repeatedly discharged a large volume of positive charge. Although the repeated streamer sequences appeared to be a characteristic feature of the EIP and were presumably involved in initiating it, the EIP sferic evolved independently of VHF‐producing activity, supporting the idea that the sferic was produced by relativistic discharge currents. Moreover, the relativistic currents during the main sferic pulse initiated a strong NBE‐like event comparable in VHF power (115 kW) to the highest‐power NBEs.