Negative Lightning Discharges Research Articles

Аномальный грозовой процесс на территории Ростовской области

The work examines the anomalous thunderstorm process that occurred on the territory of the Rostov region on June 27, 2023. This thunderstorm process was observed in other regions of the North Caucasus, but the greatest intensity of thunderstorm activity was observed in the territory of the Rostov region, where the thunderstorm lasted more than a day. The analysis of thunderstorm activity was carried out using data from the lightning direction network of the Federal State Budgetary Institution "High Mountain Geophysical Institute". During the day, about 60,000 lightning strikes were recorded in this territory, of which 7,635 were ground strikes. Of the registered 7635 ground-based lightning discharges in the Rostov region, negative lightning amounted to 6625, and positive lightning – 1010. The share of negative lightning discharges from the total number of ground-based lightning discharges in the specified territory was 87 %. The largest number of negative lightning (more than 70 %) had values up to 20 kA. More than 50 % of positive lightning discharges had values from 21 to 40 kA. The average value of the negative polarity currents was -19.19 kA, and the positive polarity was +39.7 kA. Such a large-scale thunderstorm process is a consequence of regional climate change. When carrying out lightning protection measures for facilities in the Rostov region, it is recommended to take into account abnormal values of thunderstorm activity.

Responses of the AC/DC Global Electric Circuit to Volcanic Electrical Activity in the Hunga Tonga‐Hunga Ha'apai Eruption on 15 January 2022

AbstractResponses of the AC and DC global electric circuits (GECs) to the large eruption of the Hunga Tonga‐Hunga Ha'apai (HT‐HH) volcano on 15 January 2022 are discussed. The AC‐related investigation is based on Schumann resonance (SR) measurements from six stations on four continents. The DC‐related investigation utilizes atmospheric electric field (potential gradient, PG) measurements from six recording stations in Europe and the USA. According to data from the GLD360 and WWLLN lightning detection networks, the peak lightning stroke rate, 83/s, was dominated by negative polarity lightning, but the distributions of positive and negative lightning discharges in latitude and longitude around the volcano differed. A global intensification of SR is apparent in connection with the enhanced lightning activity caused by the eruption. SR data‐based results confirm that the lightning activity in the eruption dominated the naturally occurring global activity for a period of about 1 hr. The highly localized increase in lightning activity over HT‐HH was a unique point source of SR excitation. PG measurements suggest that impulse‐like charging of the DC GEC, by ∼15%, via negative cloud‐to‐ground lightning strokes took place twice during the eruption. A time constant of 7 or 8 min has been inferred for near‐surface PG changes due to these enhancements. This could be the first direct measurement of the time constant of the GEC near the Earth's surface, as well as the first observation of the direct charging of the DC GEC by a unique atmospheric electrified source.

New insights into the lightning discharge processes

This review covers selected results of recent observations of lightning discharges performed across the entire electromagnetic spectrum (radiofrequency, optical, and energetic radiation) at the Lightning Observatory in Gainesville, Florida. The most important results include (a) characterization of the preliminary-breakdown, stepped-leader, and return-stroke processes in high-intensity (⩾50 kA) negative lightning discharges, (b) the first high-speed video images of bidirectional leader that made contact with the ground and produced a return stroke, (c) discovery of negative stepped leader branches colliding with the lateral surface of neighboring branches of the same leader, (d) new data on the occurrence context and properties of compact intracloud discharges, and (e) observation of a terrestrial gamma-ray flash that occurred during a bipolar cloud-to-ground lightning discharge. The results serve to improve our understanding of the physics of lightning with important implications for lightning modeling, lightning protection, and high-energy atmospheric physics studies.

Statistical analysis of negative cloud-to-ground lightning characteristics in Bogota, Colombia based on electric field measurements

This paper studies the electric field parameters of negative cloud-to-ground (CG) lightning flashes in the Bogota savanna (a large plateau located in central Colombia), and its comparison with other regions. This work is the first of its kind in the country where the parameters of lightning-generated electric fields are analyzed in detail. A total of 329 CG lightning flashes had been examined. These flashes were recorded within 4–250 km from the measuring station during the period August–November 2016. From observations, negative CG flashes comprised 93% of total events registered. It has been found that negative lightning discharges occurred along the plateau (4250 km2 at 2550 m altitude) exhibit some different characteristics compared with measurements carried out in several regions (tropical, subtropical and temperate latitudes). In this study, it was found that 64.7% of the negative CG flashes are multiple strokes with an average multiplicity of 2.58 strokes per flash. In addition, the mean interval between 789 negative return strokes (306 first- and 483 subsequent strokes) was 61.3 ± 51.9 ms, while the arithmetic mean of the total duration for 198 multiple-stroke flashes was 149.5 ms. Other lightning flash features such as relation between the interstroke interval and the return stroke order, the ratio of the subsequent stroke peak field to the corresponding first one and the maximum multiplicity are also analyzed.

A Study of Preliminary Breakdown and Return Stroke Processes in High-Intensity Negative Lightning Discharges

Using an automated data processing algorithm, we examined electric field records of 5498 negative cloud-to-ground flashes reported by the U.S. National Lightning Detection Network (NLDN) within 50 to 500 km of the Lightning Observatory in Gainesville (LOG), Florida. Out of the 5498 flashes, 3496 (64%) had detectable preliminary breakdown (PB) pulse trains. Only 3077 flashes with a single PB pulse train and NLDN-reported first-return-stroke (RS) peak current ≥50 kA were selected for detailed analysis. The arithmetic mean values of PB pulse train duration, PB-RS interval, and PB/RS pulse peak ratio were 2.7 ms, 8.8 ms, and 0.15, respectively. The PB-RS interval was found to decrease with increasing RS peak current (Spearman correlation coefficient was statistically significant and equal to −0.80). The range-normalized PB pulse peak exhibited statistically significant positive correlation with the RS peak current, with Spearman correlation coefficient being 0.48. Thus, it appears that the high-intensity (≥50 kA) negative lightning is characterized by shorter (and, by inference, faster) stepped leaders and more pronounced PB pulse trains.

Experimental observations of strengthening the neutron flux during negative lightning discharges of thunderclouds with tripolar configuration

We consider neutron bursts (Yakutsk cosmic ray spectrograph,105m above sea level) and the electric field during lightning discharges. It was found that the neutron bursts are observed in the negative lightning discharg only. We discuss the possibility of generation of neutrons in the lower part (the point of impact into the ground) lightning discharge.

First experimental observations of neutron bursts under thunderstorm clouds near sea level

The connection of short-term neutron bursts near sea level with the electric and geomagnetic atmospheric fields during thunderstorms in 2009–2011 has been experimentally studied. The data from the cosmic-ray spectrograph named after Kuzmin, an electrostatic fluxmeter, and a three-component fluxgate magnetometer in Yakutsk have been analyzed. It has been shown that short-term (no longer than 4 min) neutron bursts are due to negative lightning discharges. The bursts are detected at the ground level 1–3 km below thunderstorm clouds. In this case, the neutron flux is about 4 × 10−3 cm−2 s−1. The minimum energy of the neutrons that are efficiently detected by the monitor is about 10 MeV. It has been found that short-term neutron bursts are detected when the electric field strength reaches a threshold value of −16 kV/m.

Percentage of summer positive & negative lightning discharges and lightning current at the dissipating stage

Percentage of summer positive & negative lightning discharges and lightning current at the dissipating stage

Spatial Distribution of High Current Lightning Discharges in Hokuriku Area in Winter

The electric field waveforms associated with lightning discharges that were observed simultaneously with faults of power transmission lines in winter are analyzed. Also, electric field waveforms associated with high current lightning discharges in winter around the coastline of the Sea of Japan are analyzed for comparison. All of the negative lightning discharges simultaneously observed with transmission line faults produced different field waveforms from those produced by normal cloud-to-ground strokes. Positive high-current lightning discharges, however, produce field waveforms which look more like those produced by normal cloud-to-ground strokes. These high-current lightning discharges distribute differently around the coastline depending on their polarities.

The contribution of intense lightning discharges to the global atmospheric electric circuit during April 1998

Global observations of intense positive and negative lightning discharges over the continents and the oceans are summarised in mean diurnal variations of hourly integrated charge moment changes for comparison. The intense positive lightning discharges contribute a net decrease to the global atmospheric electric field. This global circuit decrease by intense positive lightning discharges is conservatively estimated to be ∼0.005–0.04% on the 1 min time scale, which can be detected by a global network of atmospheric electric field measurement instruments with a nominal sensitivity ≲5– 120 mV/m to support the traditional concept of the global circuit.

Lightning effects at high altitudes: sprites, elves, and terrestrial gamma ray flashes

A fascinating set of newly discovered complex phenomena indicate that thunderstorms and lightning discharges are strongly coupled to the overlying upper atmospheric regions. Lightning discharges at cloud altitudes (<20 km) affect altitudes >40 km either via the release of intense electromagnetic pulses (EMPs) and/or the production of intense quasi-static electric (QE) fields. The intense transient QE fields of up to ∼1 kV·m −1, which for positive CG discharges is directed downwards, can avalanche accelerate upward-driven runaway MeV electron beams, producing brief (∼1 ms) flashes of gamma radiation. A spectacular manifestation of these intense fields is the so-called ‘Sprites’, large luminous discharges in the altitude range of ∼40 km to 90 km, which are produced by the heating of ambient electrons for a few to tens of milliseconds following intense lightning flashes. The so-called ‘Elves’ are optical flashes which last much shorter (<1 ms) than sprites, and are typically limited to 80–95 km altitudes with much larger (up to 600 km) lateral extent, being produced by the heating, ionization, and optical emissions due to the EMPs radiated by both positive and negative lightning discharges. To cite this article: U.S. Inan, C. R. Physique 3 (2002) 1411–1421.

&amp;lt;i&amp;gt;Letter to the Editor&amp;lt;/i&amp;gt; Intense oceanic lightning

Abstract. The electrodynamic properties of intense oceanic lightning discharges are compared to intense continental lightning discharges. Particularly intense negative lightning discharges with absolute charge moments &gt; 2 kC · km occur more often over the oceans than over the continents during April 1998. Intense continental lightning discharges, with negative and positive polarity, and intense positive oceanic lightning discharges primarily occur associated with mesoscale convection in the late evening. The number of intense negative oceanic lightning discharges increases in the early morning hours, probably associated with the resurgence of oceanic mesoscale convection in coastal areas. The day-to-day variability of intense negative oceanic lightning discharges exhibits a five day periodicity, possibly related to planetary waves.Key words. Meteorology and atmospheric dynamics (lightning; ocean-atmosphere interactions) – Oceanography - general (marine meteorology)

Sprites triggered by negative lightning discharges

High altitude air breakdown, manifested as “red sprites,” is reported in close association with negative cloud‐to‐ground lightning (−CG) on at least two occasions above an unusual storm on August 29, 1998. Data from high speed photometry, low‐light‐level video, and receivers of lightning electromagnetic signatures in the frequency range 10 Hz to 20 kHz are used to establish the association and indicate that the causative −CG discharges effected unusually large vertical charge moment changes (ΔMQv) of up to 1550 C · km in 5 ms. The existence of sprites caused by −CG's, rather than the regularly associated +CG's, has immediate implications for sprite models and observations.

Elves triggered by positive and negative lightning discharges

Optical flashes in the lower ionosphere due to the transient heating caused by lightning electromagnetic pulses (EMP) are unambiguously identified with the Fly's Eye photometric array. Data from a thunderstorm over Mexico recorded at Langmuir Laboratory on August 27 1997 demonstrate that relatively common negative cloud‐to‐ground lightning is a previously unrecognized major cause of elves. The spatial extent of the transient heating is shown optically to be typically at least 200–700 km laterally, indicating the possibility for accumulation of ionization effects produced by successive flashes within large nighttime thunderstorm systems. One especially bright event suggests that temporal fine‐structure in the causative very low frequency EMP can manifest itself in the photometric record of elves.

Lightning-ignited forest fires in northwestern Ontario

This study investigates the relationship between lightning activity and the occurrence of lightning-ignited forest fires in the Northwestern Region of Ontario. We found that the Duff Moisture Code (a component of the Fire Weather Index System) and the multiplicity of the negative lightning discharges were the most important variables for estimating the number of lightning-ignited fires on a daily basis for Universal Transverse Mercator zone15 in Ontario. Also, the results indicate that negative lightning ignited more fires than positive lightning discharges, which is contrary to popular belief. Nearly 50% of the variance in the forest fire occurrence data was explained using linear stepwise regression. Future work will focus on finer temporal and spatial scales.