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Abstract Surface atmospheric electric field (AEF) measurements were conducted using a Kelvin water dropper equalizer by the Japan Meteorological Agency's geomagnetic observatory at Kakioka, Ibaraki Prefecture, Japan, from 1929 to February 28, 2021. To obtain AEF data successive to the water dropper measurement, we independently installed the field mills at Kakioka. In this present study, we estimated the calibration coefficients based on comparisons between the water dropper and the field mills through parallel observations over 3 days. The results revealed that the new observations could be regarded as continuous data. Our new data from the field mills in this study have begun the process of being distributed in GLObal Coordination of Atmospheric Electricity Measurements (GloCAEM) as both archived and real‐time data in 1 min and 1 s samplings.

Surface atmospheric electric field (AEF) measurements were conducted using a Kelvin water dropper equalizer by the Japan Meteorological Agency's geomagnetic observatory at Kakioka, Ibaraki Prefecture, Japan, from 1929 to February 28, 2021. To obtain AEF data successive to the water dropper measurement, we independently installed the field mills at Kakioka. In this present study, we estimated the calibration coefficients based on comparisons between the water dropper and the field mills through parallel observations over 3 days. The results revealed that the new observations could be regarded as continuous data. Our new data from the field mills in this study have begun the process of being distributed in GLObal Coordination of Atmospheric Electricity Measurements (GloCAEM) as both archived and real‐time data in 1 min and 1 s samplings. [ABSTRACT FROM AUTHOR]

Gamma‐ray glows are observational evidence of relativistic electron acceleration due to the electric field in thunderclouds. However, it is yet to be understood whether such relativistic electrons contribute to the initiation of lightning discharges. To tackle this question, we started the citizen science "Thundercloud Project," where we map radiation measurements of glows from winter thunderclouds along Japan's sea coast area. We developed and deployed 58 compact gamma‐ray monitors at the end of 2021. On 30 December 2021, five monitors simultaneously detected a glow with its radiation distribution horizontally extending for 2 km. The glow terminated coinciding with a lightning flash at 04:08:34 JST, which was recorded by the two radio‐band lightning mapping systems, FALMA and DALMA. The initial discharges during the preliminary breakdown started above the glow, that is, in vicinity of the electron acceleration site. This result provides one example of possible connections between electron acceleration and lightning initiation. Plain Language Summary: Thunderstorms are natural particle accelerators. The strong electric field inside thunderclouds accelerates relativistic electrons, which emit gamma rays via interaction with the atmosphere. High‐energy photons generated in this process have been observed as radiation enhancements called gamma‐ray glows. Winter thunderclouds along the sea of Japan are an ideal target for monitoring glows because their altitudes are usually sufficiently low for the generated gamma‐ray photons to reach the ground. We started a new citizen science "Thundercloud Project" in this area, where we distributed radiation detectors to citizen supporters to observe glows and to reveal their relationship with the aerological condition and lightning discharges. On 30 December 2021, five of those sensors detected a glow from a single thundercloud. Two of them recorded a sudden termination of the glow coinciding with a lightning flash, which was monitored by our two radio mapping systems of FALMA and DALMA. The initial discharges of the flash started at a location about 1.6 km above the glow region with an unusually fast downward progression. This paper is the first report of our citizen science project. We discuss the possibility that accelerated electrons contribute to the initiation of lightning discharges. Key Points: We started the citizen science "Thundercloud Project," a multi‐point observation campaign of gamma‐ray glows from thunderstormsOn 30 December 2021, five radiation monitors detected a 2‐km‐long size gamma‐ray glow, which suddenly terminated with a lightning flashTwo radio mapping systems of lightning identified the initiation of the discharges, which started at a location above the glow region [ABSTRACT FROM AUTHOR]

Nowcasting of lightning occurrences is essential in tropical locations as lightening causes severe damage to life and property. This study attempts to nowcast lightning events during convective phenomena using an electric field monitor (EFM) at a tropical urban location, Kolkata (22.65°N, 88.45°E). Before the onset of heavy lightning occurrences, definite changes in the atmospheric electric field (EF) are observed, which in turn are associated with high cloud liquid water content (LWC) and low cloud base height (CBH). A model has been proposed to nowcast lightning strikes within about 17.5 km radius of the present location based on the EF standard deviation (EFSD) values. The proposed technique is tested with the lightning data provided by a collocated lightning detector, which yields a prediction efficiency of ~ 0.91 (~ 0.86), a false alarm rate of ~ 0.23 (~ 0.18), and a critical success index of ~ 0.71 (~ 0.72) with an optimal range of other performance parameters during the monsoon (pre-monsoon) periods, thereby generating an alarm 45 min before lightning events. [ABSTRACT FROM AUTHOR]

A relationship between the heliospheric magnetic field, atmospheric electric field, lightning activity, and secondary cosmic rays measured on the high mount of Lomnický Štít (2,634 m a.s.l.), Slovakia, during the declining phase of the solar cycle 24 is investigated with a focus on variations related to solar rotation (about 27 days). The secondary cosmic rays are detected using a neutron monitor and the detector system SEVAN, which distinguishes between different particles and energies. Using spectral analysis, we found distinct ∼27-day periodicities in variations of Bx and By components of the heliospheric magnetic field and in pressure-corrected measurements of secondary cosmic rays. The 27-day variations of secondary cosmic rays, on average, advanced and lagged the variations of Bx and By components by about 40° and −140°, respectively. Distinct 27-day periodicities were found both in the neutron monitor and the SEVAN upper and middle detector measurements. A nondominant periodicity of ∼27 days was also found for lightning activity. A cross-spectral analysis between fluctuation of the lightning activity and fluctuation of the heliospheric magnetic field (HMF) showed that fluctuation of the lightning activity was in phase and in antiphase with Bx and By components of the HMF, respectively, which is in agreement with previous studies investigating the influence of solar activity on lightning. On the other hand, the ∼27-day periodicity was not significant in the atmospheric electric field measured in Slovakia and Czechia. Therefore, no substantial influence of Bx and By on the atmospheric electric field was observed at these middle-latitude stations.

Based on ground observation, lightning locator and atmospheric electric field instrument data, the characteristics of lightning and atmospheric electric field in Nanchang County were analyzed. The warning effect of the atmospheric electric field instruments on lightning was studied, and the threshold of some atmospheric electric field instruments was adjusted according to the expectation of the warning accuracy rate. In Nanchang County, the annual number of thunderstorm days averaged 48.6. Lightning mainly occurred from March to August, with a maximum of 8. 8 d in August. The lightning areas were mainly concentrated in the south, followed by the north, and the frequency of lightning in the middle was relatively low. The diurnal variation of lightning was obvious, and lightning happened most frequently from afternoon to evening. Five atmospheric electric field instruments were set up according to the lightning areas of Nanchang County. The average electric field intensity on a sunny day was 0.06 , 0.05,0. 16 , 0.07, and 0. 17 kV/m respectively, with certain seasonal variations. The field intensity in June was the lowest in the whole year. The atmospheric electric field on a sunny day also had obvious diurnal variation characteristics, generally presenting the characteristics of double peaks and double valleys. The first peak of atmospheric electric field intensity appeared one hour later than that of relative humidity, and then the change trends were relatively consistent. After the adjustment, the warning accuracy rate of the atmospheric electric field instruments was greatly improved to meet the expectation. [ABSTRACT FROM AUTHOR]

This paper presents a methodology that employs the electrostatic field variations caused by thundercloud formation or displacement to generate lightning warnings over a region of interest in Southeastern Brazil. These warnings can be used to prevent accidents during hazardous operations, such as the manufacturing, loading, and test of motor-rockets. In these cases, certain equipment may be moved into covered facilities and personnel are required to take shelter. It is also possible to avoid the threat of natural and triggered lightning to launches. The atmospheric electric field database, including the summer seasons of 2007/2008 and 2008/2009 (from November to February), and, for the same period and region, the cloud-to-ground lightning data provided by the Brazilian lightning detection network – BrasilDAT – were used in order to perform a comparative analysis between the lightning warnings and the cloud-to- ground lightning strikes that effectively occurred inside the area of concern. The analysis was done for three areas surrounding the sensor installation defined as circles with 5, 10 and 15 km of radius to determine the most effective detection range. For each area it was done using several critical electric field thresholds: +/- 0.5; +/- 0.8; +/- 0.9; +/- 1.0; +/- 1.2; and +/- 1.5 kV/m. As a result of the reduction of atmospheric electric field data provided by the sensor installed in area of concern and lightning provided by BrasilDAT, it was possible, for each of the areas of alert proposals, to obtain the following parameters: the number of effective alarms; the number of false alarms; and the number of failure to warning. From the analysis of these parameters, it was possible to conclude that, apparently, the most interesting critical electric field threshold to be used is the level of 0.9 kV/m in association with a distance range of 10 km around the point where the sensor is installed.

This paper presents the integration details of an operational Atmospheric Electric Field Mill Sensor (EFM) Network for standardized and continuous operation in the region of São José dos Campos, State of São Paulo, Brazil, in order to collect and transmit real time data for studies of atmospheric electric field and support the development of a Lightning Warning System (LWS). Data collection equipments, including EFM sensors from different manufacturers, datalogger, telecommunication by 3G cellular modem and solar power energy subsystems and software were integrated. A set of graphs obtained by interpolating real time data collected by the integrated EFM network combined with lightning location data detected by the Brazilian Lightning Detection System (BrasilDAT) is also presented. [ABSTRACT FROM PUBLISHER]

It is true that such a long-range forecasting of lightning is not possible, the reason being the abrupt high value of the parameters at the time of lightning strike as compared to other weather conditions. But still a system that will predict the occurrence of lightning over few minutes or few hours will be beneficial for protection of lives and equipments. In this work, atmospheric electric field data are used for devising an alarm system for lightning. With the help of Markov chain stochastic modelling of the electric field data, probabilities of a lightning strike are calculated. [ABSTRACT FROM AUTHOR]

This paper gives a resume of the papers written in English which (a) describe some of the recording instruments in use at the Nagycenk Observatory (NCK) since the International Geophysical Year (IGY 1957-1958) and up to the present time, (b) summarise the most important and different types of observations associated with thunderstorms which have been made there, and (c) discuss their various geophysical interpretations. The paper describes the main results which have been obtained in four areas of thunderstorm associated atmospheric and geospace science within the context of Earth system science. These relate to the following parameters of atmospheric electricity: the vertical electric potential gradient just above the Earth's surface and the air-Earth current as well as the point discharge current, Schumann resonance (SR) signals of the Earth-ionosphere cavity at 8, 14 and 20 Hz, transient luminous events (TLEs), and some aspects of the behaviour of the ionosphere. Deductions from these data sets are concerned with the global lightning activity and the conductivity of the air, with diurnal, seasonal, annual and long-term variations of the SR amplitudes and resonant frequencies in terms of migrating thunderstorm centres, with transient SR excitations and with sprites and other TLEs, and with ionospheric disturbances. The paper closes with some thoughts on future research directions based on the observations at NCK and Sopron and the results achieved since the IGY. [ABSTRACT FROM AUTHOR]

Lightning is a strong discharge phenomenon that occurs in nature and poses a great threat to people's property and life safety. The generation of lightning originates from the continuous accumulation of electric charges in clouds, and the atmospheric electric field instrument, as a measurement device reflecting the most fundamental cause of lightning generation, is used to detect the occurrence of lightning, which has been very widely used due to its low price and easy installation. However, its detection results are directionless and the detection range is limited. Therefore, this paper proposed a method for spatio-temporal localization of lightning based on deep Long Short-Term Memory (LSTM) neural network and interpolation method. The time series data of electric field detected by 30 atmospheric electric field instruments was fed into deep LSTM network for training, and the prediction results were classified into five categories according to the time period of lightning occurrence by softmax function. Furthermore, data from the networked stations were interpolated using ordinary Kriging (OK) to obtain the electric potential distribution in Guangzhou city, which was used to infer the approximate area where lightning may occur. The above two algorithms passed the accuracy test respectively. Finally, two case studies were done based on LSTM-OK. The results show that it can obtain satisfactory prediction performance. • Networking 30 atmospheric electric field instruments to predict lightning. • Using deep LSTM to explore the connection between electric field and lightning. • The occurrence of lightning is classified into five categories. • Using ordinary Kriging interpolation to estimate the location of lightning. [ABSTRACT FROM AUTHOR]

Mechanisms which generate atmospheric charge are examined in order to estimate the rate of field regeneration. Energy density contained in the atmospheric electric field is examined. Charge-harvesting methods are suggested and a practical use of electrostatic motors examined. Comparisons to projected energy consumption, and comparison to other energy sources are made, and viability of tapping atmospheric charge is assessed. [Copyright &y& Elsevier]

Regional variation of electrical and lightning properties of thunderclouds is investigated by using simultaneous observations of electric field mill (EFM-100) and lightning detector (LD-350) in synergy with their radiance and bulk microphysical properties. The study is carried out over Kohima in the north-eastern and over Rampurhat in the eastern part of India (20o-30o N, 85o-96o E), during the pre-monsoon season (March–May) of 2017–2018. The occurrence of EFM-100 detected thunderclouds is found to be more over Kohima (111) compared to Rampurhat (88). Whereas, the average number of lightning flash is much higher over Rampurhat (~542 flash/thundercloud) compared to Kohima (~32 flash/thundercloud). Over both the regions, the maximum occurrence of thunderclouds is found during afternoon to evening hours. The upper whisker value in the box plot shows that thunderclouds over Rampurhat are associated with higher CAPE value (Kohima: 1100 J Kg−1; Rampurhat: 5000 J Kg−1). The diurnal variation of CAPE supports relatively early occurrence of thunderclouds over Kohima. Thunderclouds over Rampurhat persists for relatively longer duration. It is observed that overall percentage occurrence of CG lightning is more over Kohima (Kohima: −CG: 28.09% & +CG: 09.74%; Rampurhat (–CG: 12.33% & +CG: 08.60%), with relatively higher −CG lightning compared to +CG, over both the stations. On the contrary, the occurrence of IC lightning is more over Rampurhat (Rampurhat: −IC: 31.75% & +IC: 47.30%; Kohima: −IC: 36.44% & +IC: 25.72%). Over Kohima occurrence of −IC is more than the +IC, whereas over Rampurhat, the occurrence of +IC is more than −IC. The overall higher occurrence of total negative and positive discharges over Kohima and Rampurhat respectively is consistence with EFM observations. The prevalence of positive/negative discharge suggests the presence of a tripole charge structure within thunderclouds over both the regions. The upper whisker value in the box plots revels higher CG flash density, IC:CG and larger log(area) over Rampurhat (Kohima: 3.0 × 10−3 flash km−2 h−1 and Rampurhat: 4.25 × 10−3 flash km−2 h−1; Kohima: 7 and Rampurhat: 15; Kohima: 10.5 km2 and Rampurhat: 11.5 km2). The lower whisker value of cloud top temperature reveals prevalence of colder thunderclouds over Rampurhat (Kohima: 220 K; Rampurhat: 184 K). The thunderclouds over Rampurhat are found to be associated with stronger updrafts and mixed-phase processes. The study reveals that, over these two regions, the electrical and lightning properties have distinct characteristics. • Thunderclouds over Rampurhat and Kohima are found to be associated with distinct electrical and lightning properties. • Thunderclouds over Rampurhat undergo larger change in electric field, flash density and IC:CG ratio compared to Kohima. • Occurrence of CG (IC) lightning is found to be more (less) over Kohima compared to Rampurhat. • The thunderclouds over Rampurhat are found to be larger and persists for longer duration. • The thunderclouds over Rampurhat are colder and are associated with strong mixed phase processes. [ABSTRACT FROM AUTHOR]