Lightning Research Articles

Investigation of thunderstorm characteristics with severe lightning events over NE region of India

Abstract. The north eastern region (NER) of India is among the hotspot regions for thunderstorm events leading to substantial loss of lives and properties every year. A reliable thunderstorm early warning system can prevent these losses. As these events are highly dynamic, prediction becomes equally challenging. Diagnostic studies of such events could provide more understanding of lightning and storms over a region which could then be used as input for the prediction of such events. Improving the efficiency of the prediction of associated meteorological parameters could improve the prediction of thunderstorm. In this study, two thunderstorm events have been identified with high lightning flash counts, using observations from the INSAT-3D satellite and lightning detection sensors. These observations revealed that one of the events was caused by a cloud system that originated elsewhere and travelled over the area of impact while the other event was an isolated convective system that occurred over a small region. The characteristic features of thunderstorms, like vertical wind velocity, cloud ice water content, relative humidity, cloud fraction and radar reflectivity, etc. were simulated using the WRF model. These simulations were validated with the ERA-5 reanalysis data and observations from Radar and satellite data. Validation results suggest that the WRF model could predict these features associated with thunderstorm events quite reliably. The study helped to improve the severe weather warning over NER of India and the stakeholders are trained on effective utilization of such warning.

Evaluation of Indian Lightning Location Network (ILLN) and characterization of cloud-to-ground lightning over Lucknow and Shillong using an ordinary camera

Abstract. This work is showing the performance of Indian Lightning Location Network (ILLN) and lightning characteristics around Lucknow and Shillong India. Observation of ground truth using ordinary camera show the location accuracy of lightning location network. By analysing the optically observed data the average cloud to ground lightning flash detection efficiency is 78.9 percent but some of them misclassified. In addition, throughout the observation in Lucknow, authors found the average inter-stroke intervals were 139.2 ms that ranges from 34 ms to 442 ms. Further, average multiplicity and multi-channel termination of these strokes were 2.3 and 1.2 respectively. The single-stroke flashes were below 23% out of the total number of negative cloud-to-ground flashes. In contrary to the Lucknow, all the flashes observed in Shillong seem single-stroke which have lower return stroke peak currents than Lucknow. This estimation of detection efficiency and characteristics will definitely assist to understand the different scenarios of lightning in plane and hilly area over the country and help to forecasters, and modelers.

Competing mechanisms of charge-induced electric field distortion and charge-involved neutralization on surface discharge

Charge-induced surface discharge poses a critical risk to the operational reliability of high-voltage direct current gas-insulated equipment and pulsed power system. In this study, we investigate the effects of charge-induced electric field distortion and charge involvement during surface discharge by separately depositing charge spots on two dielectric layers. The results show that deposited positive charges inhibit positive streamer development, whereas negative charges facilitate it, primarily due to electric field distortion induced by deposited charges. Nevertheless, the involvement of deposited charges in streamer development predominantly exhibits a neutralizing effect, exerting an opposite influence on the streamers. This highlights a competitive relationship between deposited charge involvement and electric field distortion. Additionally, the neutralization of deposited charges with electron avalanches reduces the impact of charge-induced electric field distortion, thereby mitigating its effects on discharge.

Enhancement table tennis forehand drive ability after exercise using the return board junior high school students

The objective of this study is to assess the impact of return board-based forehand drive instruction on Central Java junior high school students in Class VIII. Experimental research employing a two-group pretest-posttest design, this study consists of a pre-treatment pretest and a post-treatment posttest. Sixteen return drill training sessions were administered to the experimental group, while the control group received no intervention. Hypothesis tests, normality tests, and homogeneity tests are all components of data analysis techniques. The findings of this study indicate that the experimental group's forehand drive ability improved significantly as a result of return board training (p-value = 0.000 < 0.05; mean difference = 4.100). In contrast, there was no discernible impact of enhancing forehand drive ability on the control group (p-value = 0.000 < 0.05). As a result, it can be concluded that instruction utilizing the return board can significantly improve the forehand driving ability of Central Java eighth-graders. To improve one's ability to execute a forehand drive, researchers propose employing a training method that utilizes the return board. The aforementioned research findings suggest that instruction utilizing the return board may significantly enhance the forehand driving proficiency of Central Java Junior High School students in grade VIII. At a significance level of 0.000, the mean difference is 4.100. To improve one's forehand driving abilities, researchers recommend selecting a training method that incorporates the return stroke as an alternative. It is crucial that the training programs are well-organized, structured, and adhere to established procedures. Scholars desiring to undertake additional investigations pertaining to the utilization of return boards are encouraged to select alternative training modalities and juxtapose them.

Observational Evidence of Negative Leader Reactivation Processes Following a Negative Return Stroke in Lightning Discharges

AbstractHigh‐time‐resolved mapping results of two rare reactivation processes following a negative return stroke are discovered and analyzed. At first, the discharges prior to the reactivation process were dominated by positive discharges lasting for tens of milliseconds in a limited space in the vicinity of a decayed negative leader channel. The positive discharges produced no detectable electric field change. Then, negative discharges started and propagated along the decayed downward negative leader channels at a speed exceeding 106 m/s for a few microseconds and produced negative electric field changes. The analysis reveals that the processes are physically distinct from recoil leaders and side discharges in terms of propagation behaviors, electromagnetic characteristics, and time scale. The possible mechanisms of the processes are discussed. The observation suggests that the reactivation processes of the negative leaders may lead to subsequent return strokes.

Pulmonary Aspiration Thrombectomy with Lightning Flash Catheter in a Young Patient with Fibrosing Mediastinitis

Pulmonary Aspiration Thrombectomy with Lightning Flash Catheter in a Young Patient with Fibrosing Mediastinitis

Modeling of natural first stroke stepped leader characteristics

The paper constitutes a novel physical approach to the different stages of negative leader stepping in cloud-to-ground lightning, starting with determination of the length of the negative streamer zone below the leader tip. The positive space leader, belonging to a pre-existing space leader, propagates towards the main leader tip, bridging the streamer zone. Such propagation time however is too short for leader thermalization. The thermalization, with associated substantial drop in the internal voltage gradient, occurs over a much longer time, through corona current injected at the tip of the moving negative space leader. The latter stage constitutes the determining factor for the time interval between steps. The model has then been applied to leaders with prospective return stroke current of 3–228 kA, leader tip height of 23–2000 m, leader charge linearly decaying to practically vanish at heights of either 2500 m or 4500 m. For the conditions investigated, the step length varies in the range 3.5 m to 39 m, the bridging time of the streamer zone by positive space leader in the range 0.8 - 3 μs, time interval between steps in the range 8.5–92 μs, yielding mean stepped leader speed in the range 1.0 - 11.6 × 105 m/s. Whenever possible the model predictions were satisfactorily compared to field measurements. Interaction between the negative downward leader and an upward connecting leader during the attachment process is out of scope of this work.

On dynamics of downward-propagating sprite streamers

An approximate approach to estimating characteristics of downward-propagating single positive sprite streamers is presented. Within the framework of this approach, the dependences of streamer radius and velocity on the altitude were obtained. The influence of changes in the altitude of streamer initiation and in the electric field at this altitude on the streamer parameters is considered. Estimates of the optical emission rate are obtained.

Does the Scenario of Connection Between the Positive Leader Tip and the Lateral Surface of the Negative Leader Exist?

AbstractBased on the high‐speed video observations obtained at the Tall‐Object Lightning Observatory in Guangzhou (TOLOG), the attachment processes of three lightning flashes seem to belong to the connections between “the lateral surface of negative leader and positive leader tip” which had never been reported before were investigated. The leader connection processes of these flashes were examined in detail, and a mechanism behind connecting behavior between the lateral surface of negative leader and positive leader tip was discussed. Observation shows that negative leaders usually have abundant branches. Although some may extinguish, they still maintain a certain conductivity. When the positive leader tip comes close to the lateral surface of the negative leader (usually a few tens of meters), the previously disappeared short branch can be reactivated. It is easier for the positive leader tip to connect the tips of these branches (whether they have been extinguished or not).

Numerical simulation of the main stage of a lightning

We present a numerical model of the main stage of a lightning discharge. Within the framework of the developed model, evolution of parameters of the current channel upon the return stroke (the lightning main stage) is described by the system of equations governing conservation of mass, momentum, total energy, along with the transmission-line equations for determining the electric potential and the total current in each channel cross section. The main characteristics of lightning at the stage of the return stroke detectable experimentally, such as gas heating in the channel to temperatures in the range of 10–40 kK, the fundamental possibility of propagation of the potential-gradient wave at a speed varying from several hundredth to several tenths of the speed of light, and the possibility of the return-stroke wave propagating a relatively long distance without substantial attenuation, are demonstrated numerically. The conclusion that the developed physical and numerical model of the lightning discharge describes physical processes that occur under real conditions qualitatively correctly can be drawn based on the results on simulation of lightning discharges of various intensity.

Continuous Initial Breakdown Development of In‐Cloud Lightning Flashes

AbstractUsing a 30–250 MHz VHF interferometer, we observed a previously unreported mode of initial lightning development inside thunderclouds. This mode is defined by continuous VHF radiation spanning several km within the first few milliseconds of lightning initiation. Following flash initiation through fast positive breakdown at high altitudes above 9 km, the VHF radiation front of upward negative streamers ascended continuously at a speed of ∼1.0 × 106 m/s, forming a continuous initial breakdown burst (CIBB) about 2 km in length. For the two CIBBs analyzed, the long and narrow CIBB channel was traversed by dart leaders that occurred later in the flash, indicating that the CIBB channel belongs to what becomes the main conducting leader channel. In contrast to classic initial breakdown pulses (IBPs) with sub‐pulses superimposed on the rising edge, CIBBs produced a series of discrete, narrow LF pulses (<10 μs) with an average time interval of 0.20 and 0.14 ms, respectively. We speculate that a CIBB is a continuously developing negative streamer system in the high electric field region at high altitudes, with connections of internal plasma channels producing LF pulses. These results have implications for physical conditions conducive to the formation of a long and continuous negative streamer system.

Ionic wind produced by volume corona discharges and surface dielectric barrier discharges: What role do streamers play?

The present study compares the ionic wind produced by volume DC and AC corona discharges, and by surface dielectric barrier discharges (DBD). On the one hand, in the case of a volume corona discharge ignited between a high-voltage needle and a grounded plate, our measurements highlight that the ionic wind velocity increases in the presence of positive breakdown streamers. On the other hand, in the case of a surface AC DBD, the ionic wind velocity decreases when streamers occur. Why such a difference? The answer is not easy and the debate remains open. However, one answer would be that the streamers occurring in a volume needle-to-plate discharge leave an abundance of positive ions in the inter-electrode space and that these ions drift because of the electric field, just after the streamer propagation. On the other hand, in the case of a surface DBD, the streamers can leave positive ions in their wake but their heads especially deposit positive ions at the location where they stop propagating, i.e. a few millimetres from the electrode (up to about 10–15 mm). Then this positive space charge deposited at a few millimetres from the active electrode edge on the dielectric surface acts as a screen against the electric field due to the applied high voltage, thus preventing the drift of the ions remaining on the surface of the dielectric, close to the electrode edge. Having said that, the reality is that this explanation is certainly very simplistic compared with the very complex phenomena taking place in these two discharges, particularly at the times when the streamers form and propagate.

An Engineering Model to Represent Positive Return Strokes—An Extension of the Modified Transmission Line (MTL) Model

An engineering model to represent positive return strokes is introduced as an extension of the Modified Transmission Line model with Linear Current Decay (MTLL). This extension is grounded in experimental data on the electric fields and currents associated with positive return strokes. The core premise of the model is that once the return stroke front reaches the cloud, recoil leader-type activities within the cloud feed the lightning channel with a positive charge. This positive charge then travels to the ground in the form of an M-component, enhancing both the amplitude and duration of the impulse current in the channel and at ground level. The propagation of the return stroke current along the channel follows the MTLL model, while the M-component is treated as a current pulse traveling from the cloud to the ground. At ground level, the M-component current is fully reflected. The model successfully generates electromagnetic fields that resemble those observed from positive return strokes, and it is easily applicable to studies involving the interaction of positive return stroke fields with power lines and the Earth’s upper atmosphere.

Evolution from a guided-streamer mode to a continuous-discharge mode in an atmospheric pressure argon plasma jet

Atmospheric pressure plasma jet (APPJ) has attracted much attention due to its versatile applications in various fields, which normally operates in either a guided-streamer mode or a continuous-discharge mode. In this paper, temporal evolution is observed from the guided-streamer mode to the continuous-discharge one in an argon APPJ excited by a sinusoidal voltage. Waveforms of voltage and current indicate that the voltage applied to the electrode is distorted severely from the ideal sine. For the guided-streamer mode, there is only one discharge pulse per half voltage cycle. For the mode transition or the continuous-discharge mode, there is only one discharge composed of a pulse and a hump per half voltage cycle. Fast photography implemented for the mode transition reveals that both the discharges in the positive and the negative voltage polarities evolve from the guided-streamer mode to the continuous-discharge one. In the guided-streamer mode of the mode transition, the discharge behaves as a positive streamer in the positive voltage polarity, while a negative streamer in the negative voltage polarity. In addition, the mode transition only occurs in a range of dissipated power and gap width. Based on optical emission spectroscopy, temporal evolutions of the mode transition are investigated for excited electron temperature, electron density, and field strength. Moreover, their spatial distributions along the argon stream are studied at different time instants. These results are of great importance for the discharge dynamics of APPJ.

Initiation of Downward Positive Leader Beneath the Negative Leader Channel

AbstractDue to the weak radiation generated by positive leaders, our understanding of how positive leaders are initiated and reach the ground remains limited. This study investigated positive cloud‐to‐ground (CG) lightning induced after the long intracloud lightning based on high‐speed video and fast antenna mapping results. Below the cloud base in the field of view, re‐breakdowns of decayed negative branches occurred consecutively beneath the horizontal negative channel in the form of bidirectional leaders. These bidirectional leaders advanced along the same channel, and eventually, the third reached the ground, generating a positive return stroke (RS) with a peak current of 157 kA. Following the RS, new negative discharges emerge adjacent to the vertical return stroke channel, persisting and propagating to form a continuing current (CC) lasting over 200 milliseconds.

Calculating Radio Emissions of Positive Streamer Phenomena Using 3D Simulations

AbstractWe study radio emissions from positive streamers in air using 3D simulations, from which the radiated electric field is computed by solving Jefimenko’s equations. The simulations are performed at using two photoionization methods: the Helmholtz approximation for a photon density and a Monte Carlo method using discrete photons, with the latter being the most realistic. We consider cases with single streamers, streamer branching, streamers interacting with preionization and streamer‐streamer encounters. We do not observe a strong VHF radio signal during or after branching, which is confirmed by lab experiments. This indicates that the current inside a streamer discharge evolves approximately continuously during branching. On the other hand, stochastic fluctuations in streamer propagation due to Monte Carlo photoionization lead to more radio emission being emitted at frequencies of 100 MHz and above. Another process that leads to such high‐frequency emission is the interaction of a streamer with a weakly preionized region, which can be present due to a previous discharge. In agreement with previous work, we observe the strongest and highest‐frequency emission from streamer encounters. The amount of total energy that is radiated seems to depend primarily on the background electric field, and less on the particular streamer evolution. Finally, we present approximations for the maximal current along a streamer channel and a fit formula for a streamer's current moment.

Electromagnetic Model of K‐Changes

AbstractK‐changes are observed as step‐like increases in the thundercloud electric fields. The K‐changes occur in the late part of intra‐cloud lightning or during negative cloud‐to‐ground lightning between return strokes. It has been shown that the processes leading to K‐changes initiate in the decayed part of a positive leader channel and propagate toward the flash origin. They are often accompanied by microsecond‐scale electric field pulses. We introduce a new model to simulate processes leading to the K‐changes in cloud‐to‐ground lightning. Our method is based on the full solution of Maxwell's equations coupled to Poisson's equation for the thundercloud charge structure. To model the K‐changes, we gradually increase the decayed channel conductivity. The modeled current wavefront propagates due to the K‐processes downward along a vertical channel and completely attenuates before reaching the ground. We derive the evolution of the linear charge densities and the scalar electric potential along the channel leading to K‐changes. We model electrostatic step‐like changes in the measured electric field together with the approximate rates and amplitudes of the microsecond scale pulses. Step‐like changes increase their amplitudes with the length of the simulated channel and with a higher conductivity of the channel. The microsecond‐scale pulse waveshapes depend mainly on the propagation velocity of the current wave, and the time scale of the conductivity increase. We show that our modeled waveforms are in a good agreement with observations conducted in Florida.

Comparison of interfacial injected energy between simulated lightning return stroke experiment and common Joule heat & Arc heat model application

A previous study has shown that the thermal damage of the Joule thermal arc heat transfer model is lighter than that of a natural lightning strike. Therefore, this paper focuses on the return stroke current and proposes an improved experimental method of simulated return damage without using arc-inducing wire. Combining the data with the inversion model of injected energy, the energy transfer characteristics of the samples are characterized. Furthermore, a data dimensionality reduction method based on multiple correlation coefficients is used to discuss the impact of the current peak/rise rate/wave tail time on the injected energy discrepancy. The results indicate a positive correlation between the current peak and current rise rate with the injected energy discrepancy. When the tail time exceeds 15 microseconds, the injected energy discrepancy decreases as the tail time increases. The thermal source characteristics of energy transfer during the return stroke process are determined. During the initial phase of the return stroke current, interfacial energy transfer includes contributions from ion enthalpy flux, Joule heating, and electronic enthalpy flux. When the tail time exceeds 15 microseconds, the contribution of ion enthalpy flux to the injected energy diminishes with increasing tail time.

Protrieve Sheath embolic protection during venous thrombectomy: early experience in seventeen patients

PurposeThe Protrieve Sheath (Inari Medical; Irvine, CA) is designed for embolic protection during venous thrombectomy. This report describes experience with its use.Materials and methodsBetween November 2022 and December 2023 (13 months), seventeen patients, including nine (52.9%) females and eight (47.1%) males (mean age 58.8 ± 13.3 years, range 37–81 years), underwent deep venous thrombectomy following the Protrieve Sheath placement for embolic protection. Gender, age, presenting symptoms, procedural indications, obstructed venous segments, the Protrieve Sheath access and deployment sites, thrombectomy devices utilized, need for stent reconstruction, technical success, clinical success, adverse events (the Protrieve Sheath maldeployment or clinically significant embolic events), removed thrombi analyses, and mortality were recorded. Technical success was defined as successful deployment of the Protrieve Sheath funnel central to the thrombectomy site. Clinical success was defined as improvement in presenting venous occlusive symptoms without procedure-related venous thromboembolism.ResultsThe most common presenting symptom was extremity swelling (n = 15; 88.2%). Nine (52.9%) patients had malignant and eight (47.1%) had benign etiologies of venous obstruction. Obstructed venous segments included the inferior vena cava (IVC) and lower extremity (n = 9; 52.9%), isolated lower extremity (n = 4; 23.5%), isolated IVC (n = 2; 11.8%), thoracic central veins and superior vena cava (n = 1; 5.9%), and isolated thoracic central vein (n = 1; 5.9%). The Protrieve Sheath access sites included the right internal jugular vein (n = 15; 88.2%) for IVC and lower extremity obstructions and the right common femoral vein (n = 2; 11.8%) for thoracic central vein and superior vena cava obstructions. The Protrieve sheath funnel deployment locations included intrahepatic IVC in 13 patients (n = 13; 76.5%), suprarenal IVC in two (n = 2; 11.8%), and inferior cavoatrial junction in two (n = 2; 11.8%). Thrombectomy devices used included the ClotTriever System (Inari Medical) (n = 15; 88.2%), the InThrill Thrombectomy System (Inari Medical) (n = 4; 23.5%), the FlowTriever System (Inari Medical) (n = 2; 11.8%), the Lightning Flash 16 Aspiration System (Penumbra; Salt Lake City, UT) (n = 2; 11.8%), the Cleaner Rotational Thrombectomy System (Argon; Plano, TX) (n = 1; 5.9%), and the RevCore Thrombectomy System (Inari Medical) (n = 1; 5.9%). Ten (58.8%) patients required stent reconstruction following thrombectomy. Technical success was achieved in all patients. Clinical success was achieved in 16 (94.1%) patients. No immediate adverse events, including the Protrieve Sheath maldeployment or clinically significant embolic events, occurred.ConclusionUse of the Protrieve Sheath during large-bore venous mechanical thrombectomy resulted in favorable technical and clinical outcomes without device-related adverse events or clinically significant thromboembolic events.

Observation of Electrical Alignment Signatures in an Isolated Thunderstorm by Dual‐Polarized Phased Array Weather Radar and the Relationship With Intracloud Lightning Flash Rate

AbstractThe electrical alignment signatures of ice crystals in the middle and upper parts of a thunderstorm have a physical connection with the strong electric fields within the cloud. By taking advantage of the high spatio‐temporal resolution of an X‐band dual‐polarized multiparameter phased array radar, this paper employs negative KDP signatures to investigate the variation of electric fields in an isolated thunderstorm within its evolution, and the relationship between the negative KDP signatures and intracloud (IC) lightning activity. The results show that the radar‐inferred strong electric fields distributed in a region of about 8.5–10 km during the developing stage, then extended from about 10 km to the cloud top during the mature stage, with an increasing IC lightning flash rate before the end of the mature stage. Subsequently, the electric fields weakened associated with a large amount of IC lightning discharges. The qualitative analysis results indicate that the evolution of the radar‐inferred electric fields associated with the upper charge regions is consistent with the electrification process in the isolated thunderstorm, inferred by the IC lighting activity. In addition, there is a tendency for the increased IC lightning rate as the decrease in average composite KDP in the middle and upper layers of the thunderstorm, with a time lag of about 5.5 min between the minimum average composite KDP and the peak IC lightning rate, while a good correlation between the negative KDP volume and the IC lightning flash rate at a lag of approximately 9 min.