Ionospherically reflected proton whistlers Vavilov, D. I.; Shklyar, D. R.
Journal of geophysical research. Space physics,
December 2014, Letnik:
119, Številka:
12
Journal Article
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Odprti dostop
We present experimental observations and detailed investigation of the variety of proton whistlers that includes transequatorial and ionospherically reflected proton whistlers. The latter have ...previously been indicated from numerical modeling of spectrograms. The study is based on six‐component ELF wave data from the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite which permits to obtain not only spectrograms displaying the power spectral density but also such wave properties as the polarization, wave normal angle, wave refractive index, and normalized parallel component of the Poynting vector. The explanation of various types of proton whistlers is based on the properties of ion cyclotron wave propagation in a multicomponent magnetoplasma, with special consideration of the effect of ion hybrid resonance reflection. Analysis of experimental data is supplemented by numerical modeling of spectrograms that reproduces the main features of experimental ones. As a self‐contained result, we provide conclusive experimental evidences that the region illuminated by a lightning stroke in the Earth‐ionosphere waveguide may spread over a distance of 4000 km in both hemispheres.
Key Points
First experimental observation of ionospherically reflected proton whistlers
Estimation of lightning‐illuminated region in the Earth‐ionosphere waveguide
Detailed study of ion hybrid resonance reflection for proton‐cyclotron waves
La stèle 3 de la Bretellière, qui devait mesurer dans les 4m, a subi trois déplacements au cours des XXe et XXIe siècles qui l’ont marquée de plusieurs altérations (cassures, raclages). La découverte ...de signes gravés, en 2012, a permis un premier levé d’une composition apparentée aux programmes iconographiques inventoriés en Morbihan. La stèle était intégrée à un ouvrage linéaire comprenant au moins huit monolithes, dont deux sont encore érigés et un seul couché. La reprise des données photogrammétriques, acquises en 2012, permet aujourd’hui de produire un nouveau modèle 3D du support et d’établir un corpus d’images sous éclairages rasants virtuels mieux à même d’inventorier les anomalies en creux (gravures, désordres). La synthèse graphique confirme la présence d’une représentation de cétacé et d’une crosse, et ajoute l’existence d’un serpent et d’un quatrième motif malheureusement trop effacé pour le nommer.
Stele 3 of Bretellière, which measured around 4m, underwent three movements during the 20th and 21st centuries and remains marked by several alterations (breaks, scrapes). The discovery of engraved signs in 2012 allowed a first survey of the composition, similar to the iconographic programs known in Morbihan. The stele was part of a stone row with at least eight monoliths, two of which are still standing and one lying. The resumption of photogrammetric data acquired in 2012 allows to produce a new 3D model of the slab and to build a body of virtual shrinking images better able to inventory the anomalies in the hollows (engravings, disturbances). The graphical synthesis confirms the presence of a cetacean representation and a crook sign, and adds the existence of a snake and a fourth pattern unfortunately erased too far to conclude.
Basic provisions of the scientific and engineering fundamentals of the methods of an artificial initiation of the downward lightning and intracloud lightning by the model hydrometeor arrays have been ...formulated. The key role played by the model hydrometeor size and form on the probability of an artificial initiation of the downward lightning and intracloud lightning has been established. Volume hydrometeors of centimeter size are tailored for such goals. Dividing of the model hydrometeors on the five classes differing on the electric field amplification coefficient has been proposed. Model hydrometeors with the amplification coefficient from 5 to 19 will be the most optimal for an artificial lightning initiation. It was found that the requirements for the sizes and parameters of the model hydrometeor families and to the places of their introduction in a thundercloud will be determined in most by the effect of the earlier appearance of the avalanche corona on the hydrometeors. It discharges the nearest parts of the thunderstorm cells leading to the local decreasing of the field strength, probability of the streamer corona initiation, and its transition into the volume leader. It was determined that the combining of the model hydrometeors in the group by the dielectric string or tape and the simultaneous introduction in thundercloud of some hydrometeor arrays will significantly increase the probability of the artificial initiation of the intracloud lightning and lightning “cloud–ground,” and the successful discharging of a thundercloud. Moreover, the minimal linear sizes of separate hydrometeor groups should be more than several dozens of centimeters. Some variants of the disposition of the model hydrometeor groups in a thundercloud (near the bottom boundary of the thunderstorm cell, inside the thunderstorm cell, and in the space between the thunderstorm cells) when the most optimal conditions for the initiation of the intracloud lightning and lightning “cloud—ground” are provided, have been proposed.
In the frame of this study, the rain and lightning activity produced by rainfall events in the central and eastern Mediterranean has been studied. The analysis focuses on the study of the rainfall ...events that occurred during a period of 6 months spanning from October 2003 up to March 2004. The data used consist of 6-h accumulated precipitation amounts reported by an average number of 220 rain gauges of the surface network and the lightning strokes detected by the ATD system operated by the UK Meteorological Office. It was found that for almost 50% of the cases when rain was recorded but in absence of lightnings, the 6-h accumulated precipitation was smaller or equal to 1 mm. This percentage drops to about 15% for the cases in presence of lightnings. The distribution of 6-h accumulated precipitation without lightnings presents a clear maximum at 1 mm while the distribution in presence of lightnings presents a clear maximum at 10 mm and an important swift towards larger precipitation amounts.
The characterization of lightning flash occurrence processes is key to risk analysis. Based on it, the degree of exposure of structures to direct lightning strikes can be determined, and thus, the ...level of protection required by the protection system can be properly set. Several studies attest that lightning flash occurrence is a natural phenomenon whose parameters vary in time and space. Looking in detail the process of occurrence leads to identification of features that allow classifying it as a member of the family of stochastic processes called counting processes. This paper offers a proposal to conceptualize the lightning flash occurrence as a Non Homogeneous Poisson type counting process, in contrast to other existing approaches which are based on the statistical concept of independent and identically distributed samples (iid) that is used in statistical inference of random variables. To justify the approach, a number of considerations is set out, including formal theoretical aspects in the field of probability and statistics, along with the analysis of the variability measure in the approach involving iid. Additionally, the paper also considers the question of statistical estimation and inference process of occurrence of lightning from the perspective of stochastic processes, offering methodological approaches that are considered useful in modeling as-Nonhomogeneous Poisson Process.
The origin of outages occurring in a power distribution network are highly related with the weather conditions existing during its apparition. Wind, rain and lightnings usually are the trigger causes ...of power network outages, hence the analysis of the relationship between weather and network outage information plays an important role for forecasting the impact of future weather conditions in the power distribution network. In this paper, weather information and distribution-network outages collected during three years are studied and statistically analyzed. From the analysis some useful relationships between weather conditions and network outages were extracted.
Within the Charlotte, North Carolina, to Atlanta, Georgia, megaregion (Charlanta), the Atlanta metropolitan area has been shown to augment proximal cloud‐to‐ground (CG) lightning occurrence. Although ...numerous studies have documented this “urban lightning effect” (ULE) with regard to CG lightning, relatively few have investigated urban effects on distributions of total lightning (TL). Moreover, there has yet to be a study of the ULE using TL observations from the Geostationary Lightning Mapper (GLM). In an effort to fill this gap, we investigated spatial distributions of TL around the cities of Atlanta, GA, Greenville, SC, and Charlotte, NC, using GLM data collected during the warm seasons of 2018–2021. Analyses reveal augmentation of TL intensity and frequency over the major cities of Atlanta and Charlotte, with a diminished urban signal over the smaller city of Greenville. This work also demonstrated the potential efficacy of the emerging satellite‐based TL climatology in ULE studies.
Plain Language Summary
Studies using ground‐based lightning detection networks have revealed an “urban lightning effect” (ULE) around major cities. In 2016, the U.S. launched a weather satellite with a unique lightning mapping instrument. This study, possibly for the first time, demonstrated the ability to utilize space‐based observation of total lightning to detect the ULE within the Charlotte, North Carolina, to Atlanta, Georgia, urban corridor. The study also paves the way for future ULE analyses as the satellite lightning data record lengthens.
Key Points
The urban lightning effect (ULE) is detectable in Geostationary Lightning Mapper total lightning observations
The ULE is most discernible in the larger metropolitan areas of the Charlotte, NC, to Atlanta, GA, urban corridor
The emerging Geostationary Lightning Mapper data set enables a new generation of urban lightning studies as the record lengthens
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