摘要:

The transmission-line model previously developed for the leader stroke is applied to the return-stroke of a lightning channel. The charge stored in the corona is converted into current, by a discharge wave. The dependence of propagation velocity on coronal charge and radius leads to front steepening and the development of a jump discontinuity or electromagnetic shock in a finite time.

ISSN:0272-6343    

DOI:10.1080/02726348708908182

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We present a transmission line model for the lightning return stroke. This model incorporates a model for the corona surrounding the charged lightning channel as well as a model for the evolution of the channel incorporating hydrodynamics, energy losses, joule heating. We find that the model reproduces the “double exponential” shape of the observed field in the radiation zone, without imposing a priori the time behavior of the current pulse. The decrease in field at late times precedes any decrease in current, and is due to a lengthening of time scale. The current pulse is substantially altered as it progresses up the lightning channel, and the radiation zone signal is not of the same shape as the current pulse at any position or time.

ISSN:0272-6343    

DOI:10.1080/02726348708908183

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The natural frequencies are calculated for a metallic post with a lightning channel attached. Two different lightning channel models are discussed and the asymptotic antenna technique is employed to solve the problem formulated in terms of an integro-differential equation. The results are presented by way of figures and approximate analytic formulas.

ISSN:0272-6343    

DOI:10.1080/02726348708908184

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

After the initial processes in a natural lightning event, there can exist clouds of positive and/or negative ions in air. This paper considers some of the processes involved in the subsequent motion of such ion clouds in spherical and cylindrical geometries. In the case of spherical geometry, such a cloud can stay around for a long time. Such clouds of ions can also be moved by other electric fields in the environs.

ISSN:0272-6343    

DOI:10.1080/02726348708908185

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726348708908186

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This article reviews the current knowledge on the very high frequency electromagnetic radiation of lightning. A phenomenology analysis of the new results obtained from the study of natural and triggered lightning in New Mexico (TRIP 82), at St. Privat d'Allier in Haute-Loire, France (1983), and in 1984 in South West France (Front 84) is first described. The authors then present the spectral and temporal characteristics of the VHF-UHF radiation which can be applied to the electromagnetic compatibility of systems. From a synthesis of the experimental and theoretical contributions, they propose a hypothesis on the lightning initiation process and on the mechanisms generating lightning radiation.

ISSN:0272-6343    

DOI:10.1080/02726348708908187

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We analyzed the characteristics of the VHF (63 MHz) radiation and correlated wideband electric field records for 113 cloud-to-ground (CG) flashes and 33 intracloud (IC) flashes in five different storms in South Florida during the summer of 1981. Each of the stepped leaders in the CG flashes was preceded by active VHF radiation with an average duration of 34 msec. In 28% of the CG flashes, preliminary variations in the electric field records were observed which are similar to the B,I,L pattern reported by Clarence and Malan (1957). In these cases, the VHF radiation started only a few milliseconds prior to the preliminary electric field change. The VHF pulse repetition rate increased from the beginning of the preliminary breakdown to a few milliseconds prior to the return stroke at which time it decreased. There was a variation in the VHF pulse rate at about the time of stepped leader initiation determined by the first steady electric field change. The VHF radiation started at the same time as the electric field change in all the IC flashes. The uniqueness of the combined patterns in the VHF and electric field records suggests that a system can be designed to discriminate between CG and IC flashes tens of milliseconds prior to the occurrence of a potential return stroke. For 25 of the flashes displayed with l-µsec resolution, the ground-based electric field and the 2 MHz envelope of VHF radiation were correlated with the electromagnetic field with a bandwidth of 20-MHz recorded at an altitude of about 4 km in a WC-130 aircraft. These records showed that the VHF radiation observed at the ground correlates much better with the wider bandwidth field than the lower frequency electric field.

ISSN:0272-6343    

DOI:10.1080/02726348708908188

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726348708908189

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726348708908190

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This paper summarizes some techniques developed for electromagnetic measurements of lightning electromagnetic fields at Langmuir Laboratory. These included measurement of transient electric and magnetic fields at the ground surface, use of these fields to estimate location of the lightning and properties of the source, and use of time of arrival at different sensors to locate the source. These measurements are compared to acoustic and photographic measurements of the same events.

ISSN:0272-6343    

DOI:10.1080/02726348708908191

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor