Sferics

The properties of sferics (the electric and magnetic fields generated by electrified clouds and lightning flashes) are briefly surveyed; the source disturbance and the influence of propagation being examined. Methods of observing sferics and their meteorological implications are discussed. It is concluded that close observations of electrostatic and radiation fields are very informative, respectively, upon the charge distribution and spark processes in a cloud; that ground-level sferics stations can accurately locate the positions of individual lightning flashes and furnish valuable knowledge on the properties of the discharges; but that satellite measurements only provide general information on the level of thundery activity over large geographical regions

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Development of a VHF broadband interferometer to investigate unsolved lightning phenomena: high-energy radiation from lightning strikes and multi-stroke positive cloud-to-ground flashes

Tesi en modalitat de compendi de publicacions.(English) The aim of this thesis work is the development of a VHF broadband interferometer for lightning research. The observations with this instrument allowed us to investigate some unsolved aspects of lightning related with the high-energy emissions from lightning strikes and the occurrence of multi-stroke positive cloud-to-ground flashes sharing the same channel to ground. This Ph.D. project is contextualized in the European program: Science and Innovation with thunderstorms (SAINT), funded by the Horizon 2020 / Marie Sklodowska Curie Action, grant agreement ID: 722337. A VHF broadband interferometer is an instrument capable of mapping lightning flashes with extremely high temporal resolution. This feature, combined with the omnidirectional field of view and the ability to map lightning within the cloud, makes this instrument really promising for scientific lightning research. Its use is enriched and enhanced by the installation of other detectors or measuring instruments. In this way, it is possible to simultaneously observe with several instruments the same lightning flash and obtain complementary information needed to advance in the understanding of the physical phenomena. The main technical challenge of this work was to build our own version of a broadband VHF digital interferometer. This kind of instrument is still a prototype, off the market, and although some books and scientific papers describe how it works, its hardware and software implementation requires a lot of work and refinements to achieve the high performance required by the scientific research. Once the instrument was built and validated, field campaigns were carried out in Spain, Colombia and Italy. Observations made with our VHF broadband interferometer in coincidence with other instruments such as the high-energy detectors, electric field antenna, and Lightning Mapping Array (LMA) have made it possible to make some progress in understanding some unsolved aspects of lightning physics. The results of our research have been published mainly in the two scientific articles that constitute this Ph.D. thesis. The first article of this compendium presents measurements in coincidence of high-energy radiation with the lightning mapping provided by the VHF broadband interferometer. During a field campaign in north-central Colombia, several intense X-ray bursts were detected from negative stepped leaders and dart leaders. A strong temporal correlation has been observed between the high-energy emissions and the most intense VHF pulses, which suggests the runaway electrons as a shared mechanism. We observed multiple high-energy sources belonging to different leader branches and we speculate that the high-energy emissions could occur more often than expected. We speculated a few possible implications for TGFs. The second article presents the first observation of a multi-stroke positive cloud-to-ground lightning flash sharing the same channel to ground mapped with a VHF broadband interferometer and a Lightning Mapping Array. We propose a mechanism to describe this rare phenomenon and we identify in a fast recoil leader or a fast breakdown a crucial role in reconnecting these previously decayed leader channels and initiating the subsequent positive stroke. We investigated the polarity asymmetry of subsequent strokes.(Español) El objetivo de este trabajo de tesis consistió en desarrollar un interferómetro de banda ancha en Very High Frequency (VHF) para la investigación de rayos. Las observaciones con este instrumento nos permitieron investigar algunos aspectos no resueltos de las descargas eléctricas atmosféricas relacionadas con emisiones de alta energía al igual que ocurrencia de rayos a tierra de polaridad positiva que comparten el mismo canal. Este proyecto de doctorado está en el marco del programa europeo Ciencia e Innovación con tormentas eléctricas (SAINT) financiado por la ayuda Horizonte 2020 / Marie Sklodowska Curie, grant agreement: 722337. Un interferómetro de banda ancha VHF es un instrumento capaz de mapear los rayos con una resolución temporal de alta velocidad. Esta característica, combinada con el campo de visión omnidireccional y la capacidad de mapear los rayos dentro de la nube, hace que este instrumento sea realmente prometedor para la investigación científica de los rayos. Su uso se enriquece y mejora con la instalación de otros detectores o instrumentos de medición. De este modo, es posible observar simultáneamente con varios instrumentos el mismo relámpago y obtener información complementaria necesaria para avanzar en el entendimiento de los fenómenos físicos asociados con los rayos. El principal reto técnico de este trabajo ha sido construir nuestra propia versión de un interferómetro digital VHF de banda ancha. Este tipo de instrumento es todavía un prototipo fuera del mercado, y aunque algunos libros y artículos científicos describen su funcionamiento, su implementación de hardware y software requiere aún mucho más trabajo y perfeccionamiento para lograr su alto rendimiento. Una vez construido y validado el instrumento, se realizaron campañas de observación en España, Colombia e Italia. Las observaciones realizadas con nuestro interferómetro en conjunto con otros instrumentos como los detectores de alta energía, la antena de campo eléctrico y el Lightning Mapping Array (LMA) han permitido avanzar en la comprensión de algunos aspectos no resueltos de la física del rayo. Los resultados de nuestras investigaciones se han publicado principalmente en dos artículos científicos que constituyen esta tesis doctoral. El primer artículo de este compendio presenta las mediciones de rayos proporcionada por el interferómetro en coincidencia con detecciones de alta energía producidas por el mismo fenómeno atmosférico. Durante una campaña de campo en el centro-norte de Colombia, se detectaron varias ráfagas intensas de rayos X producidos por líderes escalonados negativos y líderes dardos. Se ha observado una fuerte correlación temporal entre las emisiones de alta energía y los pulsos VHF más intensos, lo que sugiere un mecanismo compartido con lo runaway electrons. También se observaron múltiples fuentes de alta energía pertenecientes a diferentes ramas de líderes, lo que podría sugerir que las emisiones de alta energía pueden ocurrir con más frecuencia de lo esperado. Especulamos algunas posibles implicaciones para la producción de TGFs. El segundo artículo presenta por primera vez la observación de un rayo de polaridad positiva con múltiples descargas subsecuentes que comparten el mismo canal a tierra y mapeado con el interferómetro y el sistema Lightning Mapping Array. Con esta segunda publicación proponemos un mecanismo para describir este extraño fenómeno en el que identificamos en un líder de retroceso rápido o fast breakdown como un papel crucial en la reconexión de estos canales de líderes rápidos iniciales con en el inicio de la siguiente descarga subsecuente positiva. A su vez, investigamos la asimetría de la polaridad de los líderes de rayos con las descargas subsecuentes a tierra. Por último, en el apéndice se presentan otras mediciones y los documentos del material suplementario de ambos artículos.Postprint (published version

Evaluation of Geostationary Lightning Mapper performance using the Colombia-Lightning Mapping Array

The Geostationary Lightning Mapper (GLM) on the Geostationary Operational Environmental Satellites - R (GOES-R) series satellites is the first operational lightning mapper flown in a geostationary orbit, which provides continuous observations of lightning. In order to make use of these data for improving nowcasting of severe weather and for data assimilation, it is important to characterize and understand the detection capabilities of GLM. Observations from 3-dimensional VHF Colombia Lightning Mapping Arrays (COL-LMA) provide a valuable basis for evaluating the spatial accuracy and detection efficiencies of observations from the recently launched, optical-based Geosynchronous Lightning Mapper (GLM). This Bachelor Final Thesis results of comparing spatially and temporally the individual event (pixel) level for sets of individual discharges from the LMA and GLM observations. The focus is on a representative sample of case studies encompassing different forms of convective organization at different times of day and night. The detection efficiency of GLM relative to LMA will be characterized in terms of the flash number, size, power and height among others

Thunderstorms, lightning, sprites and magnetospheric whistler-mode radio waves

Thunderstorms and the lightning that they produce are inherently interesting phenomena that have intrigued scientists and mankind in general for many years. The study of thunderstorms has rapidly advanced during the past century and many efforts have been made towards understanding lightning, thunderstorms and their consequences. Recent observations of optical phenomena above an active lightning discharge along with the availability of modern technology both for data collection and data analysis have renewed interest in the field of thunderstorms and their consequences in the biosphere. In this paper, we review the electrification processes of a thunderstorm, lightning processes and their association with global electric circuit and climate. The upward lightning discharge can cause sprites, elves, jets, etc. which are together called transient luminous events. Their morphological features and effects in the mesosphere are reviewed. The wide spectrum of electromagnetic waves generated during lightning discharges couple the lower atmosphere with the ionosphere/ magnetosphere. Hence various features of these waves from ULF to VHF are reviewed with reference to recent results and their consequences are also briefly discussed. © Springer Science+Business Media B.V. 2009

A Strong Pulsing Nature of Negative Intracloud Dart Leaders Accompanied by Regular Trains of Microsecond-Scale Pulses

We report the first observations of negative intracloud (IC) dart-stepped leaders accompanied by regular trains of microsecond-scale pulses, simultaneously detected by shielded broadband magnetic loop antennas and the radio telescope Low Frequency Array (LOFAR). Four investigated pulse trains occurred during complicated IC flashes on 18 June 2021, when heavy thunderstorms hit the Netherlands. The pulses within the trains are unipolar, a few microseconds wide, and with an average inter-pulse interval of 5–7 μs. The broadband pulses perfectly match energetic, regularly distributed, and relatively isolated bursts of very high frequency sources localized by LOFAR. All trains were generated by negative dart-stepped leaders propagating at a lower speed than usual dart leaders. They followed channels of previous leaders occurring within the same flash several tens of milliseconds before the reported observations. The physical mechanism remains unclear as to why we observe dart-stepped leaders, which show mostly regular stepping, emitting energetic microsecond-scale pulses.</p