Cloud-to-ground Discharges Research Articles

Modeling the Neuruppin ball lightning incident

In 1994, a 370-kA positive cloud-to-ground (CG) discharge 5 km east of Neuruppin, Germany was immediately followed by the production of at least ten ball lightning objects seen by numerous eyewitnesses. We propose a sequence of events based on observations of upward lightning triggered by CG flashes which can explain how a large ground-level electric field (∼1 MV m−1) could be produced by negative leaders extending into a region of positive charge above Neuruppin, resulting in transfer of a large amount of charge horizontally between the CG discharge and the region of high electric field. This model provides a causal link between the large CG discharge east of Neuruppin and the large ground-level fields which were associated with the production of ball lightning. Recommendations follow for producing ball lightning in a large laboratory experiment.

Mesoscale convective systems as a source of electromagnetic signals registered by ground-based system and DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite

Abstract. Mesoscale convective systems (MCSs) are especially visible in the summertime when there is an advection of warm maritime air from the west. Advection of air masses is enriched by water vapour, the source of which can be found over the Mediterranean Sea. In propitious atmospheric conditions, and thus significant convection, atmospheric instability or strong vertical thermal gradient leads to the development of strong thunderstorm systems. In this paper, we discuss one case of MCSs, which generated a significant amount of +CG (cloud-to-ground), −CG and intracloud (IC) discharges. We have focused on the ELF (extremely low frequency; < 1 kHz) electromagnetic field measurements, since they allow us to compute the charge moments of atmospheric discharges. Identification of the MCSs is a complex process, due to many variables which have to be taken into account. For our research, we took into consideration a few tools, such as cloud reflectivity, atmospheric soundings and data provided by PERUN (Polish system of the discharge localisation system), which operates in a very high frequency (VHF) range (113.5–114.5 MHz). Combining the above-described measurement systems and tools, we identified a MCS which occurred in Poland on 23 July 2009. Furthermore, it fulfilled our requirements since the thunderstorm crossed the path of the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) overpass.

Estimation of the IC to CG Ratio Using JEM‐GLIMS and Ground‐Based Lightning Network Data

AbstractThe occurrence ratio of intracloud (IC) to cloud‐to‐ground (CG) discharges, which is denoted by Z‐ratio, is the crucial parameter for the studies on the global electric circuit. However, the latitudinal and regional dependences of Z‐ratio are not fully clarified. Therefore, using optical data obtained by the Global Lightning and Sprite Measurements on Japanese Experiment Module (JEM‐GLIMS), we distinguished the lightning discharge type, that is, IC, positive CG (+CG), and negative CG (−CG) discharges, and statistically estimated the Z‐ratio. We analyzed 8,354 lightning events that obtained by JEM‐GLIMS observation and succeeded in identifying 4,431 IC discharges, 597 +CG discharges, and 3,326 −CG discharges. From this result, we calculated the Z‐ratio over many regions around the world and estimated its latitudinal and regional dependences. It is found that the Z‐ratio over the continental area is larger than the oceanic area. We also found that the Z‐ratio significantly decreases with the latitude, which is generally comparable to the results shown in the previous studies. The estimated Z‐ratio varies from 2.9–0.29 from the equator to 50° latitude, and the global mean value is 1.6. The regional dependence of Z‐ratio derived from this study can be combined with the CG lightning data provided by the ground‐based lightning detection networks to estimate the occurrence number of IC discharges. Then, the occurrence number of both IC and CG discharges can be used for calculating a more accurate estimation of the total lightning currents in the global electric circuit.

Ukrainian segment of the ENTLN (LIGHTNING FINDING SYSTEM)

The Ukrainian segment of the Earth Networks lightning finding system created in 2016 is dis-cussed in the paper. It consists of 12 sensors located in different parts of Ukraine which allow identifying both types of lightning: "cloud-to-ground discharge (CG)" and "cloud-to-cloud dis-charge (CC)". The stated number of sensors covers the entire territory of Ukraine and allows the determination of CG with a probability of 95 % with the spatial accuracy of lightning detection constituting about 200 meters. Taking into account the necessity to preserve the equipment, an agreement was reached with the Ukrainian Hydrometeorological Centre on installation of light-ning finding sensors within the territory of meteorological stations. Significant advantage of this lightning finding system is that it allows recording of electromagnetic lightning signals within the range from 1 Hz to 12 MHz. Due to this, the spatial position of CG and CC can be determined more accurately by analyzing the spectrum of electromagnetic signal within the specified range. To localize a lightning discharge using the ENTLN network the method of lightning finding based on the principle of "time of signal arrival (ToA)" is applied. The primary data obtained from the lightning finding sensors are analyzed in the internal system of centralized processing and can be used further by a consumer in two ways: either directly, or serve as output data for series of prod-ucts resulted from processing using mathematical, statistical and geographic information systems. In order to process obtained data the UHMI developed a modular system that allows unification of the means of primary and secondary processing of output data and enabling all necessary channels for transmission of generated data using a wide range of protocols. To visualize the lightning data a subsystem based on the open GeoServer for preprocessing of the geodata and client tools using the mapping data of OpenStreetMap are used. As an example of one of possibilities these lightning data provide, the analysis of the spatial and temporal distribution of lightning activity over the ter-ritory of Ukraine from June 10 to September 30, 2016 has been done and the results showed that these data could be a new, qualitative source of data for climatological studies. In addition, real-time data acquisition allows creation of a series of products for a wide range of consumers inter-ested in a short-term forecasting.

Spatial–temporal patterns of cloud-to-ground lightning over the northwest Iberian Peninsula during the period 2010–2015

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.

Modeling of X‐ray Images and Energy Spectra Produced by Stepping Lightning Leaders

AbstractRecent ground‐based measurements at the International Center for Lightning Research and Testing (ICLRT) have greatly improved our knowledge of the energetics, fluence, and evolution of X‐ray emissions during natural cloud‐to‐ground (CG) and rocket‐triggered lightning flashes. In this paper, using Monte Carlo simulations and the response matrix of unshielded detectors in the Thunderstorm Energetic Radiation Array (TERA), we calculate the energy spectra of X‐rays as would be detected by TERA and directly compare with the observational data during event MSE 10‐01. The good agreement obtained between TERA measurements and theoretical calculations supports the mechanism of X‐ray production by thermal runaway electrons during the negative corona flash stage of stepping lightning leaders. Modeling results also suggest that measurements of X‐ray bursts can be used to estimate the approximate range of potential drop of lightning leaders. Moreover, the X‐ray images produced during the leader stepping process in natural negative CG discharges, including both the evolution and morphological features, are theoretically quantified. We show that the compact emission pattern as recently observed in X‐ray images is likely produced by X‐rays originating from the source region, and the diffuse emission pattern can be explained by the Compton scattering effects.

Investigation of isolated thunderstorms lightning activity over eastern Mediterranean using Meteosat rapid scan infrared imagery

ABSTRACTAn analysis of selected spatiotemporal characteristics of isolated thunderstorms in relation to cloud-to-ground (CG) lightning over part of the eastern Mediterranean is performed. The purpose of the study is twofold: to better understand and improve the basic knowledge of the physical mechanisms of the phenomenon and to offer new means of nowcasting the lightning activity in such thunderstorms. Meteosat Second Generation (MSG) Rapid Scan Service (RSS) infrared imagery which offers the option of tracking the examined storms with a time frequency of 5 minutes is one of the two utilized datasets, the other being ZEUS very low frequency (VLF) lightning detection system’s CG discharge data. It was shown that a cloud top temperature of about −20°C is required for the onset of lightning activity. A rapid drop of the cloud-top temperature of about 11°C in 5 minutes on average is observed a few minutes before or during lightning initiation. The maximization of the activity is usually quite close to the overall minimum cloud-top temperature of the cell. A temperature increase of 3.5°C from this overall minimum can mark the end of the activity, which is also associated to the time evolution of the cell’s horizontal extent. In fact, after the cell’s horizontal area stops to increase and/or starts to gradually diminish, CG lightning activity is expected to stop.

Luminosity in the initial breakdown stage of cloud‐to‐ground and intracloud lightning

AbstractWe present simultaneously measured luminosity and electric field data from the initial breakdown (IB) stage in seven cloud‐to‐ground (CG) and eight intracloud (IC) lightning discharges along with, in three cases, radar and Lightning Mapping Array (LMA) data. The data were taken in north‐central Florida in 2013 and 2014. Seven CG discharges had an arithmetic mean (standard deviation, SD) IB stage luminosity pulse train duration of 3 ms (2 ms), and within the seven CG discharges, 30 luminosity pulses had the following means (SD): 10% to 90% risetime 25 µs (16 µs), full width at half maximum 68 µs (21 µs), and delay between onset of the electric field pulse and associated luminosity pulse 8 µs (8 µs). Eight IC discharges had a mean (SD) IB stage luminosity pulse train duration of 11 ms (4 ms), and within the 8 IC discharges, 37 luminosity pulses exhibited mean risetimes, widths, and delays of 59 µs (36 µs), 176 µs (70 µs), and 34 µs (20 µs), all significantly greater than in the CG case. The roughly 10 LMA sources associated with each of the three IB stages in 2014 are grouped horizontally within about 1 km2. The mean altitude (SD) of the LMA points during two CG IB stages is 5 km (600 m) and 4.3 km (250 m) and during one IC discharge is 6.2 km (550 m). We discuss the role of optical scattering in delaying and distorting the observed luminosity waveforms.

An analysis of five negative sprite‐parent discharges and their associated thunderstorm charge structures

AbstractIn this study we analyze the discharge morphologies of five confirmed negative sprite‐parent discharges and the associated charge structures of the thunderstorms that produced them. The negative sprite‐parent lightning took place in two thunderstorms that were associated with a tropical disturbance in east central and south Florida. The first thunderstorm, which moved onshore in east central Florida, produced four of the five negative sprite‐parent discharges within a period of 17 min, as it made landfall from the Atlantic Ocean. These negative sprite‐parents were composed of bolt‐from‐the‐blue (BFB), hybrid intracloud‐negative cloud‐to‐ground (IC‐NCG), and multicell IC‐NCGs discharges. The second thunderstorm, which occurred inland over south Florida, produced a negative sprite‐parent that was a probable hybrid IC‐NCG discharge and two negative gigantic jets (GJs). Weakened upper positive charge with very large midlevel negative charge was inferred for both convective cells that initiated the negative‐sprite‐parent discharges. Our study suggests tall, intense convective systems with high wind shear at the middle to upper regions of the cloud accompanied by low cloud‐to‐ground (CG) flash rates promote these charge structures. The excess amount of midlevel negative charge results in these CG discharges transferring much more charge to ground than typical negative CG discharges. We find that BFB discharges prefer an asymmetrical charge structure that brings the negative leader exiting the upper positive charge region closer to the lateral positive screening charge layer. This may be the main factor in determining whether a negative leader exiting the upper positive region of the thundercloud forms a BFB or GJ.

Multiple Lightning Discharges in Wind Turbines Associated With Nearby Cloud-to-Ground Lightning

This paper presents the analysis of five events where simultaneous lightning currents were registered in different wind turbines of a wind farm with lightning monitoring equipment installed. Measurements from current monitoring devices installed at the wind turbines and observations from auto-triggering video cameras were correlated with data from the U.S. National Lighting Detection Network. In all five events, the correlation showed that a cloud-to-ground (CG) lightning stroke with high peak current struck the ground within 10 km of the affected turbines at the time of the currents in the wind turbines. The polarity of the CG discharges was negative in two events and positive in the three remaining events, which were also accompanied by small intracloud pulses. According to the analysis of the data for each event, the simultaneous discharges at the wind turbines are most likely caused by the nearby CG strokes, involving mechanisms that vary depending on the polarity of the associated CG stroke. The analysis also suggests that the event of upward lightning from wind turbines triggered by nearby lightning activity occurs very often and therefore it should be considered carefully in the processes of assessing the lightning exposure of the wind turbines, designing the lightning protection, and defining validation tests.

낙뢰와 대기전계의 탐지를 기반으로 하는 자동낙뢰경보시스템의 구성과 운용특성

It is important to give lightning warning prior to a cloud-to-ground (CG) discharge within an Area of Concern (AOC) because most of lightning damage and victim are usually occurred by the first lightning in the AOC. The aim of this study is to find the optimal operation conditions of the automated lightning warning systems in order to make the best use of the available data. In this paper, the test-operated results of the automated lightning alert and risk management system (ALARM) based on detections of CG discharge and eletrostatic field and optimized at probability of lightning have been described. It was possible to obtain the following warning performance parameters: probability of detection (POD), false alarm ratio (FAR), probability of lightning (POL) and failure-to-warn rate<BR>(FTW). The data obtained from trial operation for 5months were not sufficient but the first analysis of domestic lightning warning was carried out. We have observed that the evaluated statistical results through trial operation depend on the various factors such as analysis methods and criteria, topographical conditions, etc. Also we suggest some methods for improvement of POL and POD including the finding of the optimal electric field threshold level to be used, based on the high values of FAR and FTW found in this work.

The VLF fingerprint of elves: Step‐like and long‐recovery early VLF perturbations caused by powerful ±CG lightning EM pulses

AbstractSubionospheric VLF recordings are investigated in relation with intense cloud‐to‐ground (CG) lightning data. Lightning impacts the lower ionosphere via heating and ionization changes which produce VLF signal perturbations known as early VLF events. Typically, early events recover in about 100 s, but a small subclass does not recover for many minutes, known as long‐recovery early events (LORE). In this study, we identify LORE as a distinct category of early VLF events, whose signature may occur either on its own or alongside the short‐lived typical early VLF event. Since LORE onsets coincide with powerful lightning strokes of either polarity (±), we infer that they are due to long‐lasting ionization changes in the uppermost D region ionosphere caused by electromagnetic pulses emitted by strong ± CG lightning peak currents of typically &gt; 250 kA, which are also known to generate elves. The LORE perturbations are detected when the discharge is located within ~250 km from the great circle path of a VLF transmitter‐receiver link. The probability of occurrence increases with stroke intensity and approaches unity for discharges with peak currents ≥ ~300 kA. LOREs are nighttime phenomena that occur preferentially, at least in the present regional data set, during winter when strong ± CG discharges are more frequent and intense. The evidence suggests LORE as a distinct signature representing the VLF fingerprint of elves, a fact which, although was predicted by theory, it escaped identification in the long‐going VLF research of lightning effects in the lower ionosphere.

Cloud-to-ground lightning in Portugal: patterns and dynamical forcing

Abstract. An analysis of the cloud-to-ground discharges (CGD) over Portugal is carried out using data collected by a network of sensors maintained by the Portuguese Meteorological Institute for 2003–2009 (7 yr). Only cloud-to-ground flashes are considered and negative polarity CGD are largely dominant. The total number of discharges reveals a considerable interannual variability and a large irregularity in their distribution throughout the year. However, it is shown that a large number of discharges occur in the May–September period (71%), with a bimodal distribution that peaks in May and September, with most of the lightning activity recorded in the afternoon (from 16:00 to 18:00 UTC). In spring and autumn the lightning activity tends to be scattered throughout the country, whereas in summer it tends to be more concentrated over northeastern Portugal. Winter generally presents low lightning activity. Furthermore, two significant couplings between the monthly number of days with discharges and the large-scale atmospheric circulation are isolated: a regional forcing, predominantly in summer, and a remote forcing. In fact, the identification of daily lightning regimes revealed three important atmospheric conditions for triggering lightning activity: regional cut-off lows, cold troughs induced by remote low pressure systems and summertime regional low pressures at low-tropospheric levels combined with a mid-tropospheric cold trough.

Absolute optical energy of sprites and its relationship to charge moment of parent lightning discharge based on measurement by ISUAL/AP

Although the Quasi‐electrostatic (QE) model has been considered a basic mechanism for describing sprite generation, the relationship between sprite luminosity and the charge moment change (CMC) value, caused by the sprites' parent lightning has not been examined quantitatively. CMC value represents the energy of cloud‐to‐ground discharge (CG) and the electric field intensity above the thunderstorm. We focused on the data obtained in 2004, in which both ISUAL on board the FORMOSAT‐2 satellite and the Tohoku ELF network were operated throughout one year. We could estimate the absolute luminous intensity of sprites free from atmospheric influence with the ISUAL/Array Photometer (AP) and investigated its relationship to the charge moment of parent lightning. Absolute optical energies emitted from sprites were estimated for 14 streamer‐type sprites for the first time. The averages of the time‐integrated optical energies are 176 kJ and 119 kJ for the N2 1PG and N2 2PG bands, respectively. Furthermore, the optical energies and the charge moments of their parent lightning estimated with ELF data show a high correlation (correlation coefficient = 0.93), that is consistent, qualitatively, with the QE model. This relationship predicts that the 50% occurrence probability is located at ∼600 C km, which coincides with previous statistical studies.

Effects of lightning and sprites on the ionospheric potential, and threshold effects on sprite initiation, obtained using an analog model of the global atmospheric electric circuit

A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (∼1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere (presumed to be an equipotential surface at 80 km altitude) to ∼250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair‐weather atmosphere in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile, the effects of both negative and positive cloud‐to‐ground (CG) lightning discharges on the ionospheric potential have been estimated. A large positive CG discharge creates an electric field that exceeds the breakdown field from the ionosphere down to ∼74 km, thereby forming a halo, a column sprite, and some milliseconds later, from ∼67 km down to ∼55 km at ∼60 ms after the discharge, a “carrot” sprite. Estimates are made of the return stroke current and the thundercloud charge moment change of a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, (Coulomb.kilometers), respectively, and those at 70 km altitude are 45 kA and 360 C.km, respectively. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from recent observations. The current flowing in the highly conducting sprite reduces the ionospheric potential by ∼1 V.

Magneto-Ionic Process for Cloud Electrification

This paper presents a theory of cloud electrification by geomagnetic control. In the atmosphere, when ion-pairs produced by collision between cloud-particles are drifted in the W-E direction by the horizontal wind, the ions of opposite polarity get separated from each other under the influence of earth's magnetic field. Lorentz forces urge these ions to move in semi-circular trajectories at different altitudes, creating the positive bipolar charged structure of the thundercloud. The continuous charging process actuated by the magneto-ionic separation and the drift of the charged cloud-particles or snow crystals generate high electric fields in both vertical and horizontal planes within the cloud; as a result, Cloud-to-Ground (CG), Intra-Cloud (IC) both vertical and horizontal, and Cloud-to-Cloud (CC) discharges occur. The nature and frequency of these discharges are determined by the geomagnetic (CM) latitude of the place of observation. Maximum thunderstorm activity is expected to occur at intermediate CM latitude stations. During violent winter thunderstorms in the northern hemisphere, the direction of wind drift within the cloud becomes E-W; then a negative dipolar charge structure develops, with its N-region lying near the crest and the P-region near the bottom of the cloud. Leader strokes from such a negative dipolar cloud contribute positive charges to ground via CG discharges. This paper also includes explanations for the cause of occurrence of IC flashes at a level higher than the N-region in a positive dipolar cloud, and the role of the IC flash preceding the CG discharge, which neutralizes a part of the positive charge in the P-region. Consequently, an equal amount of negative charge becomes unbounded in the N-region, which actuates the CG leader stroke.

Early VLF perturbations caused by lightning EMP‐driven dissociative attachment

We propose a new mechanism for lightning‐induced perturbations to VLF transmitter signals known as Early VLF events. This mechanism involves electron density changes due to electromagnetic pulses (EMP) from successive in‐cloud lightning discharges associated with cloud‐to‐ground discharges (CGs), which are likely the source of continuing current and much of the charge moment change in CGs. Through time‐domain modeling of the EMP we show that a sequence of pulses can produce appreciable density changes in the lower ionosphere, and that these changes are primarily electron losses through dissociative attachment to molecular oxygen. Modeling of the propagating VLF transmitter signal through the disturbed region shows that perturbed regions created by successive horizontal EMPs create measurable amplitude changes.

Modeling elves observed by FORMOSAT‐2 satellite

The ISUAL experiment on the FORMOSAT‐2 satellite has confirmed the existence of ionization and Lyman‐Birge‐Hopfield (LBH) band emissions in elves. In this paper, an in‐depth study of the ISUAL recorded elves was carried out. Numerical simulation results of elves based on an electromagnetic finite difference time domain (FDTD) model of the emissions between 185–800 nm and of their spatial‐temporal evolution are presented. To account for the effect of atmospheric attenuation, three major attenuation mechanisms: O2, O3, and molecular Rayleigh scattering are considered. Validations of the electromagnetic FDTD model were conducted in three ways: by comparing the calculated and observed photon fluxes in the ISUAL spectrophotometric channels, by directly comparing the simulated and observed morphologies of elves, and by comparing the computed photon counts of the ISUAL Imager based on the derived peak currents for two elve‐associated NLDN (National Lightning Detection Network) cloud‐to‐ground discharges (CGs) with those recorded by the ISUAL Imager. In all three ways, very good agreement was achieved.

Evolution of lightning in an isolated hailstorm of moderate size in the tropics

Evolution of lightning activity in a tropical hailstorm of moderate size that developed in the premonsoon season at Pune (18°32′N, 73°51′E, 559 m above sea level) is studied from the measurements of surface electric field, the Maxwell current and thunder. Total flash rate is counted from the electric field record, and the cloud‐to‐ground (CG) flash rate is estimated from the visual observations. Precise timings of their occurrence were confirmed from the observations of overshoot in the Maxwell current records. The storm exhibited an almost constant rate of one CG flash every 1 to 2 min over the whole life time of the storm. The ratio of intracloud (IC) to CG flashes (IC/CG) increased with the increase in total flash rate. In the convective stage of the storm, field changes from consecutive flashes were generally found to alternate in polarity. Moreover, in this stage, field changes occur in pairs, the first field change of each pair being of negative polarity and the second one of positive polarity. The two field changes in a pair occur with an average time difference of 14.3 ± 8.4 s while two consecutive pairs appear after 29.3 ± 9.1 s. In between the convective and mature stages, our observations suggest the occurrence of the phenomenon of rain gush and the field excursion associated with falling precipitation. Development of the mature stage was marked with rapid transitions in the surface electric field and the Maxwell current polarities from negative to positive. Further, total flash rate and IC/CG ratio sharply increase, and the lightning‐induced electric field changes become almost exclusively of negative polarity. Observations suggest possibly a lifting up of the charging region in mature stage of the storm. The dissipating stage of the storm witnessed hail and rain showers, sharp transition of electric field and the Maxwell current from positive to negative polarity and occurrence of a few positive CG discharges. Our observations are consistent with the general belief that that some lightning flashes, by neutralizing and depositing charge in the region of opposite polarity, change the charge distribution so as to trigger another discharge in the storm.

Observations of the relationship between sprite morphology and in‐cloud lightning processes

During a thunderstorm on 23 July 2003, 15 sprites were captured by a LLTV camera mounted at the observatory on Pic du Midi in the French Pyrénées. Simultaneous observations of cloud‐to‐ground (CG) and intracloud (IC) lightning activity from two independent lightning detection systems and a broadband ELF/VLF receiver allow a detailed study of the relationship between electrical activity in a thunderstorm and the sprites generated in the mesosphere above. Results suggest that positive CG and IC lightning differ for the two types of sprites most frequently observed, the carrot‐ and column‐shaped sprites. Column sprites occur after a short delay (&lt;30 ms) from the causative +CG and are associated with little VHF activity, suggesting no direct IC action on the charge transfer process. On the other hand, carrot sprites are delayed up to about 200 ms relative to their causative +CG stroke and are accompanied by a burst of VHF activity starting 25–75 ms before the CG stroke. While column sprites associate with short‐lasting (less than 30 ms) ELF/VLF sferics, carrot sprites associate with bursts of sferics initiating at the time of the causative +CG discharge and persisting for 50 to 250 ms, indicating extensive in‐cloud activity. One carrot event was found to be preceded by vigorous IC activity and a strong, long‐lived cluster of ELF/VLF sferics but lacking a +CG. The observations of ELF/VLF sferic clusters associated with lightning and sprites form the basis for a discussion of the reliability of lightning detection systems based on VHF interferometry.