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Thunderstorms emit fluxes of gamma rays known as gamma-ray glows1,2, sporadically observed by aircraft1,3–7, balloons8–11 and from the ground12–18. Observations report increased gamma-ray emissions by tens of percent up to two orders of magnitude above the background, sometimes abruptly terminated by lightning discharges1,3–5. Glows are produced by the acceleration of energetic electrons in high-electric-field regions within thunderclouds8 and contribute to charge dissipation3. Glows had been considered as quasi-stationary phenomena3,5,12, with durations up to a few tens of seconds and spatial scales up to 10–20 km. However, no measurements of the full extension in space and time of a gamma-ray-glow region and their occurring frequency have been reported so far. Here we show that tropical thunderclouds over ocean and coastal regions commonly emit gamma rays for hours over areas up to a few thousand square kilometres. Emission is associated with deep convective cores; it is not uniform and continuous but shows characteristic timescales of 1–10 s and even subsecond for individual glows. The dynamics of gamma-glowing thunderclouds strongly contradicts the quasi-stationary picture of glows and instead resembles that of a huge gamma-glowing ‘boiling pot’ in both pattern and behaviour.Tropical thunderclouds over ocean and coastal regions are shown to emit gamma rays for several hours over areas of up to a few thousand square kilometres, contradicting the quasi-stationary picture of glows. [ABSTRACT FROM AUTHOR]

Two different hard-radiation phenomena are known to originate from thunderclouds: terrestrial gamma-ray flashes (TGFs)1 and gamma-ray glows2. Both involve an avalanche of electrons accelerated to relativistic energies but are otherwise different. Glows are known to last for one to hundreds of seconds, have moderate intensities and originate from quasi-stationary thundercloud fields2–5. TGFs exhibit high intensities and have characteristic durations of tens to hundreds of microseconds6–9. TGFs often show a close association with an emission of strong radio signals10–17 and optical pulses18–21, which indicates the involvement of lightning leaders in their generation. Here we report unique observations of a different phenomenon, which we call flickering gamma-ray flashes (FGFs). FGFs resemble the usual multi-pulse TGFs22–24 but have more pulses and each pulse has a longer duration than ordinary TGFs. FGF durations span from 20 to 250 ms, which reaches the lower boundary of the gamma-ray glow duration. FGFs are radio and optically silent, which makes them distinct from normal TGFs. An FGF starts as an ordinary gamma-ray glow, then suddenly increases exponentially in intensity and turns into an unstable, ‘flickering’ mode with a sequence of pulses. FGFs could be the missing link between the gamma-ray glows and conventional TGFs, whose absence has been puzzling the atmospheric electricity community for two decades.Flickering gamma-ray flashes associated with terrestrial thunderstorms have been observed, which may be the missing link between gamma-ray glows and TGFs. [ABSTRACT FROM AUTHOR]

The probabilistic approach to tropical cyclogenesis is advanced here by examining the role of convection in the early stages. The development of “hot towers”, that is tall cumulonimbus towers which reach or penetrate the tropopause, and their role in tropical cyclogenesis is investigated in two well-documented cases of formation. namely hurricane Daisy (1958) in the Atlantic and Tropical Cyclone Oliver (1993) in the Coral Sea. The hot towers in Daisy had been intensively studied by Malkus and Riehl three decades ago but remained mainly unpublished. The dynamics of Oliver genesis by merging mesoscale vortices has been recently reported, but much of the aircraft data remained. This paper adds the evolving contribution of cumulus-scale events and their associated electrification, which was made possible by the addition of an electric field mill, a numerical cloud model and other remote sensors. In their genesis stages, Daisy and Oliver appeared very different because Daisy resulted from a deepening tropical wave in the Atlantic and the pre-Oliver vortex emerged eastward from the Australian monsoon trough. However, the vertical profiles of θE in the rain areas were nearly identical, with the characteristic concave shape showing substantial midlevel minima. Therefore, both required increasing upflux of high θE subcloud air in order to accomplish the formation stage, with about two hot towers each in the nascent eyewall. In both cases, partial eyewalls developed at the edge of the convection, permitting subsidence in the forming eye, which was shown to contribute to the pressure fall. The probabilistic concept proposes that any contribution to early pressure fall raises the probability of success. When the incipient storm goes through those fragile phases more rapidly, the risk of death by the onset of unfavorable large-scale factors such as wind shear or upper-level subsidence is reduced. Daisy developed in an inactive, moist environment with light, variable winds throughout the troposphere while in Oliver, strong divergent upper outflow apparently outweighed strong wind shear, although the latter was responsible for a slow and messy development of a closed, circular eye. In both storms, the hot towers in the major rainband were taller and stronger than those in the early eyewall. Onedimensional time-dependent model runs were used to simulate both in Oliver with two important results: 1) the taller rainband clouds permitted greater high level heating, if it could be retained; and 2) greater electrification and more lighting occurred in the rainband although the partial eyewall clouds also showed strong electrification. Airborne radar, electrification measurements and models are fitted together to understand their relationship. An important result is the clear inference that fairly deep mixed phase regions existed in both eyewall and rainband, in which the DC-8 aircraft experienced liquid water at temperatures colder than −40°C below freezing. These results show that the claims of no supercooled liquid water in tropical cyclones require re-examination with the proper measurements of electricification that are now feasible. [ABSTRACT FROM AUTHOR]

We analyze the topside ionosphere power line radiation (PLR) at 60 Hz over the US using electric field data collected by CSES satellite between January 2019 and December 2022. The study aimed to further investigate the month-to-month variation characteristic of PLR occurrence rate observed by satellite and its several influencing factors, including solar radiation, lightning activity, and try to clarify the influence of electricity consumption. The results show that the solar radiation (solar zenith angle and F10.7) plays a major role in the variation of the PLR occurrence rate, and that there is no direct connection with the number of lightning. For the relationship between PLR occurrence rate and electricity consumption, the low occurrence rate associated with decreased weekend electricity consumption was not observed in the US. However, there is a significant difference in PLR occurrence rate between the East and West Coasts of the US at the same latitude during the same time period, suggesting that the significant difference in PLR occurrence rate is caused by the significant difference in electricity consumption between the two coasts. After excluding the effect of solar radiation on PLR occurrence rate, we concluded that only a significant difference in regional electricity consumption could lead to a corresponding change in PLR occurrence rate detected by the Low-Earth-Orbit satellite. Finally, we also found there is seasonal variation in the diurnal differences of the PLR occurrence rate caused by seasonal variation of the lower ionosphere. [ABSTRACT FROM AUTHOR]

Lightning flashes (LF) and their association with meteorological variables that can influence the occurrence of lightning have been assessed in detail over the Indian domain, i.e., the Convective Available Potential Energy (CAPE), Relative Humidity (RH), Total Column Water Vapour (TCWV), Surface Temperature (ST) and Outgoing Longwave Radiation (OLR). A high-resolution dataset of LF has been retrieved from the Lightning Imaging Sensor (LIS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. The CAPE, TCWV, RH and ST from 1998 to 2013 are retrieved using ERA-Interim monthly/annual climatology while OLR was retrieved from NCEP datasets. The seasonal analysis shows that most LF occur during the pre-monsoon period (March, April, and May) (0.40–0.45 flash/km2/day) over northeast region. During the monsoon season (June, July, and August), the LF dominates over northern India (0.35–0.40 flash/km2/day). The seasonal variation of CAPE shows the maximum (1250–2250 J/kg) during pre-monsoon over the coastal area of NE and SE regions. TCWV and RH show the maximum in monsoon season over northeastern part, which is 50–70 kg/m2 and 60–80%, respectively. The dependence of LF on meteorological parameters varies from region to region, as is evident from statistical analysis. Maximum LF occurred over the NE (0.049 flash/km2/day) region, followed by the EC (0.041 flash/km2/day) and the lowest in the WC (0.027 flash/km2/day) region of India. The LF showed a significant correlation with CAPE over NE and EC of India because of higher humidity content values over the coastal regions, which form graupel through convection. Over the WH, LF and CAPE showed a good correlation (r = 0.94) because of orographic convection processes. Further, TCWV showed significant correlation with LF over WH (0.89) and minimum over WC (0.23) region. Principal component analysis (PCA) shows that lightning is well correlated with CAPE, RH, TCWV and ST over most regions in India. However, lightning is not significantly correlated with OLR. Understanding the meteorology of lightning across the Indian region can inform forecasting of possible lightning events and is relevant for assessing lightning for human, wild risk and climate projections. Research highlights: The regional-scale meteorological variables associated with lightning are identified. Due to the regional orography, lightning flashes show high correlation in proximity to meteorological variables. The spatio-temporal distribution shows that most of the lightning flashes occur during March, April and May (MAM) months over North East region. The impact of meteorological variables is visible as the study's threshold values change over time. [ABSTRACT FROM AUTHOR]

Northerly low-level jets (LLJ) along the eastern Andes are important conduits of moisture transport and play central roles in modulating precipitation in South America. This study further investigates the variability of the LLJ during extended austral summers. A new method characterizes the spatial extent of the LLJ and finds four distinct types: Central, Northern, Andes and Peru. We show the existence of specific evolutions such that the LLJ may initiate in the central region, expands along the Andes and terminates in the northern region. Conversely, the LLJ may propagate from north-to-south. The spatiotemporal evolution of the LLJ is remotely forced by Rossby wave trains propagating from the Pacific Ocean towards South America, and the different phases of the wave trains favor the occurrences of Central, Northern or Andes types. Occurrences of Central and Northern types are more frequent in El Niño and La Niña years, respectively. The persistence of precipitation is shown to be directly related to the persistence of the LLJ. Lastly, the Madden-Julian Oscillation plays an important role in generating wave trains modulating the frequency of LLJ, especially the Central type. [ABSTRACT FROM AUTHOR]

A nonuniform dusty plasma, micrometer-size particles or microdroplets of which are located in a dense gas or in atmospheric air, is excited by an energy pulse leading to the weak ionization of the gas. As a result, the particles charge through the attachment of gaseous ions to them. The stability of dusty plasma is determined by the low mobility of charged microparticles. The conditions under which the separation of negative and positive charges occurs in a dusty plasma with the creation the electric field are considered. The criteria are presented for the generation of atmospheric electricity in a dense cloud as a result of the gravitational falling of charged water microdroplets in the atmosphere, the weak ionization of which occurs under the action of cosmic rays. It is shown that this is possible only under a nonuniform space distribution of water microdroplets in the cloud. The peculiarities of a dusty plasma are considered. This plasma exists in Saturn's rings and in the flow of coal combustion products, as well as in the dusty atmosphere of a coal mine. [ABSTRACT FROM AUTHOR]

Terrestrial gamma-ray flashes (TGFs) are high-energy emissions in thunderstorms that were discovered first by satellite-based and then by ground-based gamma-ray detectors with photon energy up to tens of MeV. TGFs are a natural high-energy phenomenon associated with lightning discharges that frequently occur during thunderstorms. However, their production mechanisms and associated processes are still unclear. TGF studies have already been a research spotlight in the atmospheric electricity and high-energy atmosphere research areas. In this paper, we review recent research progresses on TGF studies in the past decade, including TGF detection, the relationship between TGFs and lightning processes, and thunderstorm activities. Several unsolved important scientific questions are discussed. Results suggest that upward TGFs observed by satellite-based detectors are closely connected with the development of in-cloud upward negative leaders. They are usually generated in milliseconds of the initiation of upward negative leaders and may produce a kind of distinct radio emissions because of the generation and propagation of huge amounts of high-energy electrons. By contrast, its counterpart, i.e., downward TGFs observed by ground-based gamma-ray detectors, is associated with different types of lightning processes, such as downward negative or upward positive leaders, the initial continuing current stage of rocket-triggered lightning flashes return stroke processes. Because of limited observations, how these downward TGFs are generated is still unclear. Benefiting from the development of state-of-the-art instruments with high temporal and spatial resolutions, new insights into the processes and mechanisms of TGFs will be achieved with coordinated observations from satellite-based and ground-based measurements. [ABSTRACT FROM AUTHOR]

The International Space Station (ISS) is in the lowest available orbit at ~400 km altitude, bringing instruments as close to the atmosphere as possible from the vantage point of space. The orbit inclination is 51.6°, which brings the ISS over all the low- and mid-latitude regions of the Earth and at all local times. It is an ideal platform to observe deep convection and electrification of thunderstorms, taken advantage of by the Lightning Imaging Sensor (LIS) and the Atmosphere Space Interaction Monitor (ASIM) experiments. In the coming years, meteorological satellites in geostationary orbit (~36,000 km altitude) will provide sophisticated cloud and lightning observations with almost complete coverage of the Earth's thunderstorm regions. In addition, Earth-observing satellite instruments in geostationary- and low-Earth orbit (LEO) will measure more atmospheric parameters at a higher resolution than we know today. The new infrastructure in space offers an opportunity to advance our understanding of the role of thunderstorms in atmospheric dynamics and climate change. Here, we discuss how observations from the ISS or other LEO platforms with instruments that view the atmosphere at slanted angles can complement the measurements from primarily nadir-oriented instruments of present and planned missions. We suggest that the slanted viewing geometry from LEO may resolve the altitude of electrical activity and the cloud structure where they occur, with implications for modelling thunderstorms' effects on the atmosphere's radiative properties and climate balance. [ABSTRACT FROM AUTHOR]

Product of Bowen ratio with the sum of precipitation rate and evaporation rate has been used as proxy to evaluate the seasonal and annual spatial distributions of lightning flash rate over South/Southeast Asian region (60–120° E, 0–40° N) with 9 models from the Coupled Model Inter-comparison Project-Phase 5 (CMIP5). The model-simulated mean LFR with each model is positively correlated with the satellite-observed LFR on both seasonal and annual scales. The satellite-observed LFR is correlated with the ensemble mean LFR of the models with a correlation coefficient of 0.93 over the region. The model-simulated LFR has also been used for projection of lightning in the late twenty-first century. Overall, the projected LFR over whole study area shows a 6.75% increase during the (2079–2088) period in high radiative forcing scenario (RCP8.5) as compared to the historic period of (1996–2005). Rise in LFR is also identified using another projected period (2051–2060) and a lower radiative forcing scenario condition (RCP4.5), though lesser in magnitude, as expected. For the projected period (2051–60) in the RCP8.5 case, LFR over the domain shows an increase of 4.3%; whereas for a lower future scenario condition (RCP4.5), it indicates a rise by 5.36% at the end of the twenty-first century. Moreover, results indicate an increase in extreme events of severe convective storms with intense lightning in mountainous dry regions at the end of the twenty-first century. It is suggested that the proxy used here is favourable for projection of LFR in this region and perhaps for the whole tropical area. [ABSTRACT FROM AUTHOR]

Lightning is an electrical discharge — a 'spark' or 'flash' as charged regions in the atmosphere instantly balance themselves through this discharge. It is a beautiful and deadly naturally occurring phenomenon. In June 2020, more than a hundred people died in the state Bihar of India only in 3 days' span due to lightning events. In this study, Lightning Imaging Sensor (LIS) from the Tropical Rainfall Measuring Mission (TRMM) satellite with a very high spatial resolution of 0.1° has been utilized to create the lightning climatology of India for 16 years during the period 1998 to 2013. Diurnal, monthly, and seasonal variations in the occurrence of lightning flash rate density have also been analyzed. TRMM satellite Low-Resolution Monthly Time Series (LRMTS) with 2.5° resolution datasets have been used for lightning trend analysis. The diurnal lightning event mainly occurs in the afternoon/evening time duration (1400–1900 h) around 0.001 flashes/km2/h. The highest lightning occurred in the month of May (0.04 flashes/km2/day) and the least in December (0.005 flashes/km2/day). The distribution of lightning flash counts by season over India landmass is mainly in pre-monsoon months (MAM) which ranges from 0.248 to 0.491 flashes/km2/day, and monsoon (JJA) ranges from 0.284 to 0.451 flashes/km2/day and decreases afterward. Spatially, the distribution of lightning flash density is seen over the North-Eastern region along with Bangladesh, Bihar, Jharkhand, Orissa, and Jammu and Kashmir region. The pre-monsoon (MAM) season shows a positive trend of lightning around 0.04 flashes in the North-Eastern region and the post-monsoon (SON) shows a negative trend of − 0.021 in central India. The CAPE and K-Index have positively correlated with the flash rate density seasonally but CAPE is more significantly correlated around 0.83 during pre-monsoon and monsoon season. This study also focused on finding out the district wise lightning hotspots regions of India. Rajouri and Reasi district in Jammu and Kashmir has the highest lightning with 121 and 115 flashes/km2/yr, respectively. [ABSTRACT FROM AUTHOR]

Colombia's lightning climatology was studied using 16 years of high-resolution data from the Tropical Rainfall Measuring Mission Lightning Imaging Sensor (TRMM LIS). The findings present the climatology of the country organized in two ways: where lightning occurs and when lightning occurs. The authors sorted data using Colombia's six natural regions and conditional mean values for day, month, quarter, and year for frequency occurrence. The findings show a high mean flash rate density (FRD) around 70 fl km - 2 year - 1 in 15 % of the territory. Most of this activity concentrates in the northern part of the country between latitude 7 ∘ N and 11 ∘ N. Regarding time patterns, lightning reaches its maximum in most of the territory two times a year with a transition period marked by a steep fall. But, the areas with higher activity seem to have a single lightning season, with a maximum around August. These findings confirm the need to consider lightning activity based on regional contexts. During the day, activity is more probable from afternoon to evening in the southern part of the country; meanwhile, it tends to go from afternoon to early morning in northern regions. [ABSTRACT FROM AUTHOR]

This study investigated the correlation of thermodynamic parameters with the regional averaged lightning flash density in southwest Iran based on OTD/LIS observations and reanalysis datasets from 1996 to 2014. In addition, the most important parameters and their domains were identified for explaining the lightning density variance using a multiple linear regression model. The results showed that surface sensible heat flux over Syria and Jordan, CAPE over southwest Iran, sea surface temperature over the Arabian Sea, and latent heat flux over Northeastern Europe are the best parameters to predict the lightning density in winter. While in spring, CAPE over southwest Iran, the surface sensible heat flux over northeast Iran and the Arabian Sea, and air surface temperature over the Saudi Arabian Peninsula are the main factors for predicting lightning density. The regression models explain almost 90% and 93% of the lightning variability in winter and spring, respectively. The local effect of CAPE and low-level wind shear on lightning activity is more important in spring than in winter, indicating that the contribution of local lightning-generating convective activity is higher in spring. The correlation coefficient between humidity indices and lightning density showed that western moisture sources have a more important role in providing moisture to convection and lightning in winter than in spring. It is worth noting that the wind speed of jet streams at 300 hPa is positively correlated with lightning activity in winter, although their contribution to the multiple linear regression model is negligible. [ABSTRACT FROM AUTHOR]

Tropical forests store 40–50 per cent of terrestrial vegetation carbon1. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests2. Owing to climatic and soil changes with increasing elevation3, AGC stocks are lower in tropical montane forests compared with lowland forests2. Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1–164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network4 and about 70 per cent and 32 per cent higher than averages from plot networks in montane2,5,6 and lowland7 forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa8. We find that the low stem density and high abundance of large trees of African lowland forests4 is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse9,10 and carbon-rich ecosystems.The aboveground carbon stock of a montane African forest network is comparable to that of a lowland African forest network and two-thirds higher than default values for these montane forests. [ABSTRACT FROM AUTHOR]

The results of experimental and theoretical studies of diurnal variations in the atmospheric electric field in the surface layer are presented. The gradient of the potential of the atmospheric electric field was measured at the Cheget Peak station (3040 m above sea level) in the high-mountain zone of the Elbrus region, where no significant anthropogenic impact is available and the unitary variation features appear in the diurnal course of the electric field. An analysis of observational data has indicated that the diurnal variation of the electric field has a morning (0200–0400 UT) minimum and daytime (0600–1100 UT) and evening (1600–1900 UT) maxima, the positions of which depend on surface wind speed. Local variations are caused by electric-field perturbations resulting from the space charge at the Earth's surface due to the electrode effect and the influence of turbulent mixing. Analytical solutions of the equation for the total electric current in the region of the electrode effect have been obtained and investigated. In the case of the classical electrode effect, the oscillations of the electric field and current coincide in time, but differ in amplitude, depending on the characteristic scale of the electrode layer. In a turbulent stably stratified surface layer, if the electric field strength on the Earth's surface is constant (i.e., there is no diurnal variation), it has been found that, with an increase in the turbulence coefficient in the diurnal variation of the electric field, the maxima and minima of the diurnal variation shift by 2–3 h relative to current density fluctuations. An increased electric field slightly reduces the shift due to the increased influence of the classic electrode effect, which inhibits the effects of turbulence. [ABSTRACT FROM AUTHOR]

This paper presents the lightning activity, aerosol optical depth (AOD) and climatic parameters (Bowen ratio, relative humidity, rainfall, maximum surface temperature and maximum updraft speed) over wet (Northeast India—NEI) and dry (Northwest India—NWI) land surfaces in a comparative analysis. The analyses are performed on flash counts and weather data of 17 years (1998–2014) retrieved from the Tropical Rainfall Measuring Mission (TRMM) lightning imaging sensors (LIS) and the Moderate Resolution Imaging Spectroradiometer (MODIS), respectively. The first higher peak for flash counts during pre-monsoon (April–May) and second lower peak during September over wet NEI and dry NWI regions indicate the development of strong electrified storms during pre-monsoon and weakly electrified clouds during the withdrawal phase of the southwest summer monsoon. The monthly means of flash counts, Bowen ratio, maximum surface temperature, AOD and maximum updraft speed are higher by 27, 81, 16, 50 and 16%, respectively, for NWI than those of NEI. The relative humidity and rainfall are higher by 12% and 73% for NEI than those of NWI, respectively. The Pearson's correlation coefficients of lightning activity with climatic parameters and AOD demonstrate the distinctive orographic lifting, moisture content and vertical wind shear in the upper troposphere in the regional climatic zone of dry NWI in comparison to that of wet NEI. [ABSTRACT FROM AUTHOR]

The Earth's N2-dominated atmosphere is a very special feature. Firstly, N2 as main gas is unique on terrestrial planets in the inner Solar System and gives a hint for tectonic activity. Studying the origins of atmospheric nitrogen and its stability provides insights into the uniqueness of the Earth's habitat. Secondly, the coexistence of N2 and O2 within an atmosphere is unequaled in the entire Solar System. Such a combination is strongly linked to the existence of aerobic lifeforms. The availability of nitrogen on the surface, in the ocean, and within the atmosphere can enable or prevent the habitability of a terrestrial planet, since nitrogen is vitally required by all known lifeforms. In the present work, the different origins of atmospheric nitrogen, the stability of nitrogen dominated atmospheres, and the development of early Earth's atmospheric N2 are discussed. We show why N2–O2 atmospheres constitute a biomarker not only for any lifeforms but for a-erobic lifeforms, which were the first major step that led to highly developed life on Earth. [ABSTRACT FROM AUTHOR]

Biomass burning is one of the critical components of the Earth system, significantly affecting atmospheric emissions and carbon budgets. Fires occurring in the interface between wildland and urban areas also have important socioeconomic effects, affecting people's lives and resources. Even though fires are natural in many ecosystems, climate and societal changes have recently caused particularly severe fire seasons (Australia, California, Amazonia, Portugal...). Mitigating the negative impacts of fire requires further efforts to assess fire danger conditions. Satellite Earth observation provides considerable capabilities to evaluate the different variables involved in fire danger. Data obtained from remote sensors offer information on possible sources of fire ignition, on fuel status and abundance, and on the topography and the meteorological conditions that will affect fire spread. Satellite observations also provide near-real-time information on fire occurrence for early response teams. This article describes the different variables affecting fire danger and illustrates how satellite data can offer useful information to estimate these variables, focusing on global and continental fire danger systems. [ABSTRACT FROM AUTHOR]

Transient luminous events (TLEs) such as sprites, blue jets (BJs) and elves have been studied intensively during the last three decades, and much is now known of their properties. This progress is caused by several factors including satellite optical observations, ground-based measurements of sprite-produced electromagnetic fields, the use of high-speed video observations and telescopic cameras with high resolution that enables one to trace the dynamics of sprite and BJ development. In this paper, we review various types of TLEs, including recently discovered dancing sprites, gnomes, ultraviolet (UV) atmospheric flashes and other effects. The sprite initiation, visible evolution, streamer structure, and their relationship with intra-cloud (IC) process are discussed. Considerable study has been given to ULF/ELF measurements which can provide us with important information on the delayed sprite generation and the role played by IC processes in the perturbation of the lower ionosphere above the sprite. A set of electrodynamic and transport kinetic equations describing the TLEs are complicated because the number densities, mobilities of electrons and ions, reaction constants and other parameters are strongly dependent on altitude. Because of this, the majority of theoretical study of TLEs and other large-scale optical phenomena at high altitude are based on numerical modeling of the basic kinetic, transport and electrodynamic equations describing TLEs evolution, whereas the analytical theory remains a formidable task to be accomplished. In this paper, we review a few analytical results, which have been recently derived from simple physical models of the TLEs phenomena. In the remainder of this paper, we focus our attention on the properties of UV flashes in the mesosphere, which have been observed onboard Russian microsatellites "Universitetsky-Tanyana" and "Vernov." Such a kind of optical flash is referred to as a transient atmospheric event, which differs from the TLEs in optical energy, duration and other parameters. [ABSTRACT FROM AUTHOR]

We evaluated the performance of general atmosphere circulation model (GCM) from the European Center for Medium Range Weather Forecasts (ECMWF) for estimating surface air temperature (T) and precipitation (P) in 55 locations in the Brazilian Amazon. We compared data from surface meteorological stations obtained by the Brazilian Institute of Meteorology (INMET) and ECMWF by linear regression analysis (LRA) using R2 and Willmott et al. (J Geophys Res C5:8995–9005,1985) index (d) as measurement of precision and accuracy, respectively. We applied the Fourier series analysis by extracting the trend and frequency components of P events with noise reduction in the time series. We used the multivariate K-means method to separate weather stations by Groups of Similar Performances (GSPs). The northwest region is characterized as the area with the highest precipitation supply but the lowest performances for T and P, with R2 lower than 0.18. ECMWF tend to overestimate P in dry season and to underestimate in rainy season. The proposed methodology of calibration of P data by the Fourier series was a good tool to predict an extreme event every 5 to 7 months in the region. ECMWF presented high performance (R2 > 0.60) when estimating P in a monthly scale and medium performance (R2 < 0.60) when estimating T in a monthly and 10-day period. The highest concentrations of surface meteorological stations in the eastern/southeastern portion of the Amazon region were decisive in the ECMWF performance expression, indicating an increased meteorological predictability in the anthropic areas, precisely where the agricultural areas of grain were established in the region. [ABSTRACT FROM AUTHOR]

Thunderstorm overshooting is rare but not an unusual phenomenon in a metropolitan of India, Kolkata (22.57° N; 88.36° E) during the pre-monsoon months (April–May). An attempt is made in this study to identify the important parameters differentiating the thunderstorms in overshooting and non-overshooting categories through data analytics from 2000 to 2015. The present investigation on parametric classification would facilitate in estimating the predictability of thunderstorms with overshooting which subsequently might assist in operational forecast of thunderstorm severity over Kolkata. The altitudes of lifting condensation level (LCL), wind shear, bulk Richardson number (BRN), gust speed, boundary layer characteristics and their correlation with thunderstorm cloud top height (CTH) and also their variation and distribution during overshooting (OTS) and non-overshooting (TS) thunderstorms are analyzed in this study. The result depicts that over Kolkata the intensity of storms during OTS is higher than during TS though the frequency of OTS is less than that of TS. The results further show that the potential temperature (θ), equivalent potential temperature (θe), mixing ratio (es) in the boundary layer, convective available potential energy, convective inhibition energy, BRN and gust speed play significant roles in regulating the CTH during OTS and TS thunderstorms over Kolkata. [ABSTRACT FROM AUTHOR]

In 1999, the first sprites were observed above European thunderstorms using sensitive cameras. Since then, Eurosprite campaigns have been conducted to observe sprites and other transient luminous events (TLEs), expanding into a network covering large parts of Europe and coastal areas. In 2009 through 2013, the number of optical observations of TLEs reached a peak of 2000 per year. Because of this unprecedented number of European observations, it was possible to construct a climatology of 8394 TLEs observed above 1018 thunderstorm systems and study for the first time their distribution and seasonal cycle above Europe and parts of the Mediterranean Sea. The number of TLEs per thunderstorm was found to follow a power law, with less than 10 TLEs for 801 thunderstorms and up to 195 TLEs above the most prolific one. The majority of TLEs were classified as sprites, 641 elves, 280 halos, 70 upward lightning, 2 blue jets and 1 gigantic jet. The climatology shows intense TLE activity during summer over continental areas and in late autumn over coastal areas and sea. The two seasons peak, respectively, in August and November, separated by March and April with almost no TLEs, and a relative minimum around September. The observed TLE activity, i.e. mostly sprites, is shown to be largely consistent with lightning activity, with a 1/1000 of observed TLE-to-lightning ratio in regions with most observations. The overall behaviour is consistent among individual years, making the observed seasonal cycle a robust general feature of TLE activity above Europe. [ABSTRACT FROM AUTHOR]

Lightning, a climate-related highly localized natural phenomenon, claims lives and damage properties. These losses could only be reduced by the identification of active seasons and regions of lightning. The present study identifies and correlates the lightning-prone regions with the number of casualties reported over India at the state/union territory level. The seasonal and monthly composite satellite data of Lightning Imaging Sensor for the duration of 16 years (1998–2013) have been analyzed in this study for the identification of the major lightning-prone seasons and regions over India. The casualties due to lightning have also been estimated using data from Accidental Deaths and Suicides in India, National Crime Record Bureau report of India. The spatial distribution analysis reveals that lightning occurs mostly in hilly regions over India throughout the year (26 flash/sq. km/yr) and, however, causes lesser casualties because of the sparse population over the hilly terrain. The seasonal analysis reveals the most lightning phenomena occur during the pre-monsoon period (40–45 flash/sq. km/yr) over the northeast region of India. During the winter period, the lightning dominates over the northern parts of India such as Jammu and Kashmir. The state-wise casualties' study reveals that maximum casualties are reported in Madhya Pradesh (313 deaths), Maharashtra (281 deaths) and Orissa (255 deaths) on an average per annum. The favorable climatic conditions, such as availability of moisture content, unstable atmosphere and strong convection, cause severe cases of lightning over the regions of Orissa and Maharashtra. [ABSTRACT FROM AUTHOR]

The purpose of this research is to present a detailed description of the proposed Convergence space mission on the Russian segment of the International Space Station for the wider scientific community. The key features of the mission are (1) the necessity of creating a new type of multifrequency radio-thermal airborne complexes with a specialized set of operating frequencies and with the formation of algorithms and software for the three-dimensional recovery of the water-vapor field in the lower troposphere and for estimating the horizontal advection and convective latent heat fluxes at different altitudes and with different forms of boundaries of the investigated regions. (2) An important part of the mission is the global monitoring of optical transient activity, including lightning in cloud tropospheric systems and electric discharges in the upper atmosphere, which are accompanied by a variety of short-term optical glows, commonly called transient luminous events. A significant contribution to the elucidation of the physics and the development of models of high-altitude electric discharges is the synchronous operation of the lightning detector and gamma detector to search for and study gamma-ray bursts of terrestrial origin, including those in previously unexplored latitudes, up to ±51°. It seems that the proposed instrumental configuration and integrity of the mission, which includes the synchronous operation of devices of different ranges of electromagnetic radiation (both the microwave range and optical and gamma range) will contribute significantly to the elucidation of the physics of processes of interaction of catastrophic atmospheric phenomena of the hydrodynamic type, i.e., tropical cyclones, with the electrical activity of tropospheric cloud systems (the field of lightning discharges) and activity of high-altitude electric discharges, which, in turn, can serve as a serious experimental basis for the formation of physical ideas about the genesis of gamma-ray outbreaks of terrestrial origin. [ABSTRACT FROM AUTHOR]

On the basis of a parametrization of the ionospheric potential (IP), the seasonal dynamics of the diurnal IP variation for 2016–2017 is simulated for the first time using the Weather Research and Forecasting (WRF)-Advanced Research WRF (WRF-ARW) model. The diurnal IP variation averaged over the annual simulation period shows good agreement with the classical Carnegie curve, suggesting that the proposed parametrization correctly reproduces the basic characteristics of stationary global electric circuit generators. The annual variation shows no precise repeatability from year to year, but there is a lower IP in the Northern Hemisphere winter and a higher value in the summer. The model-derived diurnal variation demonstrates stable seasonal trends, with only one distinct IP maximum of 120% of the average at 16:00 to 18:00 UTC in the Northern Hemisphere winter and two much lower maxima (~107% of the average) in the summer: a morning maximum at 08:00 to 09:00 UTC and an evening maximum at 18:00 to 20:00 UTC. The model annual dynamics of the diurnal variation agrees with the experimental data of surface field measurements in Antarctica in 2006–2011. The proposed parameterization and the modeling technique made it possible to correctly simulate the times of IP variation maxima, their seasonal variability, and а decrease in the variation amplitude during the Northern Hemisphere summer. [ABSTRACT FROM AUTHOR]

A modification of the commonly used Price–Rind scheme for lightning flash frequency (LFF), which can be used in calculations with large spatial and time steps, has been developed. If such steps are applied, the exponent in the relationship of LFF as function of convective cloud heights is smaller by a factor of two over land and smaller by one-fourth over the ocean in comparison to the original Price–Rind scheme. The modified version has been implemented in the Climate Model of the Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM). The results of LFF simulations with the modified scheme agree better with the satellite data than with the original version. In the IAP RAS CM, global warming (cooling) leads to an LFF increase (decrease) in all seasons. The sensitivity of the LFF to surface air temperature changes at the global level is estimated at 10%/K. [ABSTRACT FROM AUTHOR]

The spatial-temporal patterns of cloud-to-ground (CG) lightning covering the period 2010-2015 over the northwest Iberian Peninsula were investigated. The analysis conducted employed three main methods: the circulation weather types developed by Jenkinson and Collison, the fit of a generalized additive model (GAM) for geographic variables, and the use of a concentration index for the ratio of lightning strikes and thunderstorm days. The main activity in the summer months can be attributed to situations with eastern or anticyclonic flow due to convection by insolation. In winter, lightning proves to have a frontal origin and is mainly associated with western or cyclonic flow situations which occur with advections of air masses of maritime origin. The largest number of CG discharges occurs under eastern flow and their hybrids with anticyclonic situations. Thunderstorms with greater CG lightning activity, highlighted by a higher concentration index, are located in areas with a higher density of lightning strikes, above all in mountainous areas away from the sea. The modeling of lightning density with geographic variables shows the positive influence of altitude and, particularly, distance to the sea, with nonlinear relationships due to the complex orography of the region. Likewise, areas with convex topography receive more lightning strikes than concave ones, a relation which has been demonstrated for the first time from a GAM. [ABSTRACT FROM AUTHOR]

In recent years, locating total lightning at the VLF/LF band has become one of the most important directions in lightning detection. The Low-frequency E-field Detection Array (LFEDA) consisting of nine fast antennas was developed by the Chinese Academy of Meteorological Sciences in Guangzhou between 2014 and 2015. This paper documents the composition of the LFEDA and a lightning-locating algorithm that applies to the low-frequency electric field radiated by lightning pulse discharge events (LPDEs). Theoretical simulation and objective assessment of the accuracy and detection efficiency of LFEDA have been done using Monte Carlo simulation and artificial triggered lightning experiment, respectively. The former results show that having a station in the network with a comparatively long baseline improves both the horizontal location accuracy in the direction perpendicular to the baseline and the vertical location accuracy along the baseline. The latter results show that detection efficiencies for triggered lightning flashes and return strokes are 100% and 95%, respectively. The average planar location error for return strokes of triggered lightning flashes is 102 m. By locating LPDEs in thunderstorms, we find that LPDEs are consistent with convective regions as indicated by strong reflectivity columns, and present a reasonable distribution in the vertical direction. In addition, the LFEDA can reveal an image of lightning development through mapping the channels of lightning. Based on three-dimensional locations, the vertical propagation speed of the preliminary breakdown and the changing trend of the leader's speed in an intra-cloud and a cloud-to-ground flash are investigated. The research results show that the LFEDA has the capability for three-dimensional location of lightning, which provides a new technique for researching lightning development characteristics and thunderstorm electricity. [ABSTRACT FROM AUTHOR]

Recent studies indicate as an important technological step the development of infrared HgCdTe-based focal plane arrays (FPAs) with sub-wavelength pixel pitch, with the advantage of smaller volume, lower weight, and potentially lower cost. In order to assess the limits of pixel pitch scaling, we present combined three-dimensional optical and electrical simulations of long-wavelength infrared HgCdTe FPAs, with 3 μm, 5 μm, and 10 μm pitch. Numerical simulations predict significant cavity effects, brought by the array periodicity. The optical and electrical contributions to spectral inter-pixel crosstalk are investigated as functions of pixel pitch, by illuminating the FPAs with Gaussian beams focused on the central pixel. Despite the FPAs being planar with 100% pixel duty cycle, our calculations suggest that the total crosstalk with nearest-neighbor pixels could be kept acceptably small also with pixels only $$3\,\mu \hbox {m}$$ wide and a diffraction-limited optical system. [ABSTRACT FROM AUTHOR]

The results of experimental investigation of the influence of model hydrometeor arrays on the stimulation of discharging processes of an artificial thunderstorm cell of negative or positive polarity are presented. It has been revealed that insertion into the thunderstorm cell of model hydrometeors of different kinds brought together in an array by different methods can increase the effectiveness of charged-cloud discharging by several times. It has been established that model hydrometeors of ellipsoid form are most effective for neutralization of the charge of a negatively charged artificial thunderstorm cell. Under conditions of a positive polarity of an artificial thunderstorm cell, its discharge is most effectively provided by model hydrometeors of cylindrical form. It has been revealed that introduction of model hydrometeor arrays also has an effect on the duration of the main discharge stage, during which the artificial thunderstorm cell discharges. It has been shown that the duration of the main stage of discharge initiated by arrays of model hydrometeors of different shapes from a negatively charged artificial thunderstorm cell is several times longer than that for a positively charged cell. The obtained data open up new possibilities for using methods of discharge intensification of a natural thundercloud. [ABSTRACT FROM AUTHOR]

The climatic effects of aerosols on the precipitation over the Amazon during the dry to wet transition period have been investigated using an atmospheric general circulation model, NCEP/AGCM, and the aerosol climatology data. We found increased instability during the dry season and delayed wet season onset with aerosols included in the model simulation, leading to the delay of the maximum precipitation over the Amazon by about half a month. In particular, our GCM simulations show that surface solar flux is reduced in the Amazon due to the absorption and scattering of the solar radiation by aerosols, leading to decreased surface temperature. Reduced surface solar flux is balanced by decreases in both surface sensible heat and latent heat fluxes. During the wet season, the subtropical system over the Amazon has a shallower convection. With the inclusion of aerosols in the simulation, precipitation in the rainy season over the Amazon decreases in the major rainfall band, which partially corrects the overestimate of the simulated precipitation in that region. The reduced surface temperature by aerosols is also coupled with a warming in the middle troposphere, leading to increased atmosphere stability and moisture divergence over the Amazon. However, during the dry season when the convective system is stronger over the Amazon, rainfall increases in that region due to the warming of the air over the upper troposphere produced by biomass burning aerosols, which produces an anomalous upward motion and a convergence of moisture flux over the Amazon and draws the moisture and precipitation further inland. Therefore, aerosol effects on precipitation depend on the large-scale atmospheric stability, resulting in their different roles over the Amazon during the dry and wet seasons. [ABSTRACT FROM AUTHOR]

In the present study, a number of atmospheric and some ionospheric anomalies are analyzed, which were recorded prior to the Mw 8.3 Illapel earthquake of September 16, 2015. This very large earthquake occurred in Central Chile, close to the coast, as the result of thrust faulting on the interface between the Nazca Plate and South American continent. Using remotely sensed data extracted from NASA/Giovanni, NOAA/NCEP, and NOAA/NGDC, atmospheric and ionospheric anomalies were observed that co-registered 35-40 and 25-30 days prior to the main shock, respectively. With reference to long-term time series over the epicentral area, significant atmospheric anomalies were recorded for cloud cover, geopotential height, precipitation rates, surface air pressure, omega, stream function, and wind vectors-all in the time window of August 5-10, 2015, 35-40 days prior to the main shock. Anomalous TEC maps were recorded for the same time period. Satellite images indicate the formation of an unusual cyclone, presumably triggered by air turbulences and abnormal atmospheric conditions over the epicentral area, including strong vertical winds. Data from the Jicamarca radio observatory in Peru, more than 2000 km to the North, reveal anomalous ionospheric variations on August 15-20, 2015 with respect to international reference ionosphere thickness parameters and the altitude of the F layer. The observed anomalies are consistent with processes that occur at the ground-to-air interface due to the stress activation of peroxy defects in the hypocentral volume. The flow of positive hole charge carriers to the Earth surface expected to have led to massive air ionization, generating at first primarily positive airborne ions, then negative air ions plus ozone. Understanding the sequence of processes inside the Earth's crust and at the ground-to-air interface provides information not previously available about the causal and temporal linkages between the various pre-earthquake phenomena and the future seismic event. [ABSTRACT FROM AUTHOR]

The decadal variation of lightning activity over Northeast India (NEI) from the year 2002 to 2011 is studied with the help of satellite-based lightning imaging sensor (LIS) data. An anomalous 56 % increase in lightning activity is observed in the year 2010 with respect to the previous years. To investigate the reason behind this increase, the LIS data are analyzed with several meteorological and cloud microphysical parameters. These parameters are convective sources of cloud ice, cloud top temperature, surface temperature, convective precipitation rate and total ice water content and convective available potential energy. On a synoptic scale, the period of anomalous lightning activity could be related to the development of an El Nino event at the middle of 2009 that broke down in the early months of the next year with a rapid transition to La Nina by August 2010. Analyses expose that El Nino Southern Oscillation might have diversely modified the local meteorological and cloud microphysical parameters. It comes out that this rapid transition from El Nino to La Nina condition could be the possible reason behind the dramatic increase in lightning activity, which was not previously documented over NEI. [ABSTRACT FROM AUTHOR]

Large-scale fields and inner-core processes relevant to the formation and intensification of Typhoon Fengshen (2008) were examined by simulations using a global nonhydrostatic model with a cloud-permitting resolution. Five runs were performed by varying the cloud microphysics or initial condition settings. In three out of five runs, a middle tropospheric trough developed within a few days following a large-scale latent heat release, which enabled the successive occurrence of deep convective events within the 50-km radius of the incipient disturbance and subsequent tropical cyclone (TC) formation. In the run initialized by altering the analysis dataset, collocation between latent heat release and the large-scale gyre was less evident, and neither the trough nor a TC developed. In the run with weaker latent heating in the lower troposphere, the trough was weak and TC formation was significantly delayed. These results indicate that the superposition of large-scale disturbances in the lower and middle troposphere and their linkage through convective enhancement played an important role in the genesis of Fengshen by preconditioning the establishment of a deep upright inner core. [ABSTRACT FROM AUTHOR]

The space between the two spherical conducting shells, Earth surface and the lower boundary of the ionosphere, behaves as a spherical cavity in which some electromagnetic signals can propagate a long distance and is called Earth-ionosphere waveguide. Through this waveguide ultra low frequency (ULF), extremely low frequency (ELF) and very low frequency (VLF) signals can propagate efficiently with low attenuation. Resonances which occur for ELF waves due to round-the-world propagation interfering with $2n \pi $ phase difference are called Schumann resonances. Lightnings are the main sources of energy continuously producing these electromagnetic radiations from the troposphere. Some fixed frequency signals are also transmitted through the waveguide from different stations for navigation purposes. The intensity and phase of these signals at a particular position depend on the waveguide characteristics which are highly influenced by different natural events. Thus the signatures of different geophysical and extra-terrestrial events may be investigated by studying these signals through proper monitoring of the time series data using suitable techniques. In this article, we provide a review on ULF, ELF and VLF signals within the waveguide in terms of different geophysical and extra-terrestrial events like lightning, earthquakes, Leonid meteor shower, solar flares, solar eclipse, geomagnetic storms, and TLEs etc. [ABSTRACT FROM AUTHOR]

A growing body of research illuminates the role that changes in climate have had on violent conflict and social instability in the recent past. Across a diversity of contexts, high temperatures and irregular rainfall have been causally linked to a range of conflict outcomes. These findings can be paired with climate model output to generate projections of the impact future climate change may have on conflicts such as crime and civil war. However, there are large degrees of uncertainty in such projections, arising from (i) the statistical uncertainty involved in regression analysis, (ii) divergent climate model predictions, and (iii) the unknown ability of human societies to adapt to future climate change. In this article, we review the empirical evidence of the climate-conflict relationship, provide insight into the likely extent and feasibility of adaptation to climate change as it pertains to human conflict, and discuss new methods that can be used to provide projections that capture these three sources of uncertainty. [ABSTRACT FROM AUTHOR]

The natural spectrum of electromagnetic variations surrounding Earth extends across an enormous frequency range and is controlled by diverse physical processes. Electromagnetic (EM) induction studies make use of external field variations with frequencies ranging from the solar cycle which has been used for geomagnetic depth sounding through the 10 $$^{-4}$$ -10 $$^4$$ Hz frequency band widely used for magnetotelluric and audio-magnetotelluric studies. Above 10 $$^4$$ Hz, the EM spectrum is dominated by man-made signals. This review emphasizes electromagnetic sources at $$\sim$$ 1 Hz and higher, describing major differences in physical origin and structure of short- and long-period signals. The essential role of Earth's internal magnetic field in defining the magnetosphere through its interactions with the solar wind and interplanetary magnetic field is briefly outlined. At its lower boundary, the magnetosphere is engaged in two-way interactions with the underlying ionosphere and neutral atmosphere. Extremely low-frequency (3 Hz-3 kHz) electromagnetic signals are generated in the form of sferics, lightning, and whistlers which can extend to frequencies as high as the VLF range (3-30 kHz).The roughly spherical dielectric cavity bounded by the ground and the ionosphere produces the Schumann resonance at around 8 Hz and its harmonics. A transverse resonance also occurs at 1.7-2.0 kHz arising from reflection off the variable height lower boundary of the ionosphere and exhibiting line splitting due to three-dimensional structure. Ground and satellite observations are discussed in the light of their contributions to understanding the global electric circuit and for EM induction studies. [ABSTRACT FROM AUTHOR]

Cloud characteristics over the rain-shadow region of the north central peninsular India has been studied using C-band radar data for the period 21 September-30 October 2011. The period covers withdrawal and post-withdrawal periods of monsoon 2011. Though the study has been carried out for one season, it has been shown that it is representative of climatic feature over the region. The cloud characteristics have been discussed in the context of large scale dynamical and thermodynamical conditions over the region using NCEP wind data and radiosonde data, respectively. The large scale dynamic and thermodynamical conditions were found favorable for occurrence of widespread and deep convection. The cloud top heights show tri-modal distribution with peaks at 2-3, 4-6 and 8-12 km which are associated with cumulus, congestus and cumulonimbus clouds, respectively. The tops of these three types of the clouds are found to be associated with the stable layers in the atmosphere. The frequency of congestus clouds was the highest. The cloud characteristics over the region differ from other tropical land and oceanic regions in respect of maximum height, mean duration and cumulative frequency distribution. Distribution of cloud top height and duration show deviation from lognormality in the lower ends. It indicates that the cloud growth mechanism is different than that observed over other tropical land and oceanic regions and also due to the large wind shear prevailed over the region. During the period, a large number of suitable clouds were found available for hygroscopic and glaciogenic cloud seeding. [ABSTRACT FROM AUTHOR]

Daily variations were studied in atmospherics at frequencies of 600 Hz and 6 kHz, which were recorded on the Kola Peninsula from 2012 to 2013 in different geomagnetic conditions. It is shown that increased geomagnetic storminess does not significantly change daily variations in the hourly mean flow and amplitudes of atmospherics at either frequency for the west-east component. For the north-south component, this is true only for hourly mean amplitudes. The distribution of amplitudes of atmospherics recorded is satisfactorily described by the well-known formula P( X) = [1 + ( X/ X)], where 1.9 < k < 2.9 for a frequency of 600 Hz and 1 < k < 2 for 6000 Hz. [ABSTRACT FROM AUTHOR]

The interrelation between gamma-ray bursts of lightning origin and high-energy electron bursts registered in near-Earth space below the radiation belt is sought and investigated. Data from the ARINA and VSPLESK satellite experiments, developed to register high-energy electron bursts with energies in the range of 3-30 MeV, and the databases of the RHESSI space observatory, which contain data on gamma flashes of geophysical origin with energies of up to 17 MeV, are used. The results from analyzing electron bursts and gamma flashes that coincide up to ten minutes in time and are located on the same L-shell are presented. [ABSTRACT FROM AUTHOR]

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The annual variation of a number of amplitude characteristics of the noise electromagnetic field in the frequency range near the first Schumann resonance (and in particular the mean values of the modulus of horizontal magnetic components and parameters of the distribution function of noise pulses over amplitudes) was obtained and analyzed based on the results of three-year measurements performed at the high-latitude magnetic observatory Lovozero. The summer increase in mean and median values of the magnetic component of noises associated with electrical storms and the lack of annual variations of the exponent that empirically describes the distribution of amplitudes of noise signals were found. The relationship between the seasonal (winter/summer in the northern hemisphere) increase in the mean value of the modulus of the horizontal magnetic field component and seasonal increase in the global number of lightning discharges is shown by the correlation of the results of satellite observations and measurements of the magnetic component. [ABSTRACT FROM AUTHOR]

Daily variations in the intensities of atmospherics at 600 Hz and 6 kHz detected at the Lovozero observatory from June to December 2012 were studied. Under quiet geomagnetic conditions, daily variations of atmospherics are shown to be determined by both the waveguide parameters of the Earth's ionosphere and the activity of storm centers. In summer, a broad daytime maximum of atmospherics flow N (the number of atmospherics per hour) is detected most likely due to the lightning activity in mid-latitude regions that are nearer to the observatory than the global storm centers. The daily variations in atmospherics mean amplitudes per hour A differ appreciably from the daily variations N, reflecting largely the changes in lighting conditions along signal propagation paths. The distribution function of the levels of atmospherics can be approximated by the following formula taken from publications: P( X) = [1 + ( X/ X)], where k is a parameter that changes from 2.2 to 3.2 at f = 600 Hz and from 1.5 to 2 at f = 6 kHz under quiet geomagnetic conditions. [ABSTRACT FROM AUTHOR]

Particle bursts (PBs), the phenomena characterized by short-term increases of particle counting rates (CRs), were observed by space-borne radiation belt particle detectors. With the electron CR data obtained by National Oceanic and Atmospheric Administration (NOAA)-18 satellite, the occurrence of PBs in the inner belt (1⩽ L⩽2 and B⩾20.5 μT) were derived for years 2006-2011. The monthly occurrence number of PBs exhibits a strong maximum in northern summer (May-August). In association with global lightning data, the seasonal occurrence of PBs is found to be consistent with the lightning activity, especially if only lightning flashes at latitudes >20° are taken into account. The positive correlation between PBs and mid-latitude lightning discharges indicates the role of lightning-induced whistler waves, and is consistent with the expected pitch-angle scattering by wave-particle interactions. The contribution of lightning is so significant that it forms a non-negligible seasonal background of PBs. If one connects PBs to seismoelectromagnetic emissions (SEME) in attempt to find the earthquake precursor, the lightning background needs to be considered with great care. [ABSTRACT FROM AUTHOR]