Lightning Mapping With an Array of Fast Antennas

Journal of Atmospheric and Solar-terrestrial Physics, 2008

We demonstrate that narrowband measurements can be used for rudimentary ranging of cloud-to-ground lightning flashes. The system at present responds to both intra-cloud and cloud-to-ground lightning; ranging is demonstrated for a subset of flashes known to be cloud-to-ground lightning. The system uses a ferrite-core antenna with a length of about 4 cm and diameter 4 mm, and operates on a narrow band at about 1 MHz, close to the HF band (3-30 MHz). It downmixes the signal to audio frequencies and operates in a manner which is very similar to an AM radio. The system triggers on all impulses which exceed a given adjustable threshold above the ambient noise level, and records 1 s of data. Such a system was used to collect lightning-caused electromagnetic disturbances during summer 2006 in Finland. The output is compared to two scientifically verified references: a flat-plate broadband antenna measuring the vertical electric field and a commercial lightning location network giving flash location. A key aim of the system is to reduce the information to as few parameters as possible. Peak intensity and full-flash energy were used as simple parameters. It is shown that accurate flashby-flash ranging is not possible with this method; however, it is shown that the method can be used to track clusters of ground flashes within a range of about 50-100 km with an accuracy of about 10 km. r

Journal of Geophysical Research, 1994

A radio interferometer system is described which utilizes multiple baselines to determine the direction of lightning radiation sources with an angular resolution of a few degrees and with microsecond time resolution. An interactive graphics analysis procedure is used to remove fringe ambiguities from the data and to reveal the structure and development of lightning discharges inside the storm. Radiation source directions and electric field waveforms have been analyzed for different types of breakdown events for two lightning flashes. These include the initial breakdown and K type events of in-cloud activity, the leaders of initial and subsequent strokes to ground, and activity during and following return strokes. Radiation during the initial breakdown of one flash was found to consist of intermittent, localized bursts of radiation that were slow moving. Source motion within a given burst was unresolved by the interferometer but was detected from burst to burst, with negative charge being transported in the direction of the breakdown progression. Radiation during initial leaders to ground was similar but more intense and continuous and had a characteristic intensity waveform. Radiation from in-cloud K type events is essentially the same as for dart leaders; in both cases it is produced at the leading edge of a fast-moving negative streamer that propagates along a well-defined, often extensive, path. K type events are sometimes terminated by a fast field change that appears analogous to the field change of a return stroke. Dart leaders are sometimes observed to die out before reaching ground; these are termed "attempted leaders" and, except for their greater extent, are no different than K type events. Several modes of breakdown during and after return strokes have been documented and analyzed. One mode corresponds to the launching of a positive streamer away from the upper end of the leader channel, apparently as the return stroke reaches the leader start point. In another mode, the quenching of the dart leader radiation upon reaching ground reveals concurrent breakdown in the vicinity of the source region for the leader. In both instances the breakdown appears to establish channel extensions or branches that are followed by later activity of the flash. Finally, a new type of breakdown event has been identified whose electric field change and source development resemble those of an initial negative leader but which progresses horizontally through the storm. An example is shown which spawned a dart leader to ground. 13,059 13,060 RHODES ET AL.: RADIO INTERFEROMETER OBSERVATIONS OF LIGHTNING w input signals larger than 3-6 dB above minimum detectable signal. The I and Q signals were averaged with 1-ps running averagers to improve the accuracy of the phase estimate and were digitized at 1-ps time intervals for subsequent processing. Flash analog-to-digital converters with 7bit resolution and 10 MHz digitizing capability were used. The resulting digital I and Q values were used as addresses to a read-only memory which performed an inverse tangent lookup operation to determine the phase difference d = tan-•(Q/I). Four phase values were thus obtained, corresponding to the short and long baselines along the orthogonal directions. Each phase value consisted of an 8-bit digital word (2 quadrant bits and 6 additional bits), in which 0 to 2•r phase difference was represented as 00-FF hexadecimal. A separate antenna and receiver measured the amplitude of the ttF radiation signal using a logarithmic detector, and a flat plate antenna was used to sense the electrostatic field change AE of the lightning discharge. The electric field change was sensed in the manner described by Krehbiei et ai. [1979] using a decay time constant of 10 s; its signal was also differentiated with a decay time of 0.1 ms and amplified by a factor of 100 to give the fast components of AE. The ttF amplitude and fast AE data values were digitized with 8-bit resolution in synchronization with the phase values and were combined with the phase values to form two 3-byte RHODES

Journal of Atmospheric and Oceanic Technology, 2005

The lightning data that are recorded with a three-dimensional lightning mapping array (LMA) are compared with data from an electric field change sensor (in this case a flat-plate antenna operated both as a “slow” and a “fast” antenna). The goal of these comparisons is to quantify any time difference that may exist between the initial responses of the two instruments to a lightning flash. The data consist of 136 flashes from two New Mexico thunderstorms. It is found that the initial radiation source detected by the LMA usually precedes the initial response of both the slow and fast antennas. In a small number of cases, the flat-plate antenna response precedes the initial LMA source, but by no more than 2 ms. The observations of such a close time coincidence suggest that the first LMA radiation source of each flash was located at or very near the flash-initiation point. Thus, the first LMA radiation source and the initial sequence of sources from a lightning flash can be used as remot...

IEEE Transactions on Electromagnetic Compatibility, 2017

A low-cost system for measuring lightning electric field waveforms (Lightning Detection and Waveform Storage System or LDWSS) is presented. The system has been developed for research and operational use in the Amazon region of Brazil. In order to quantify the magnitudes of recorded fields, the LDWSS was calibrated relative to the electric field measuring system operating at the Lightning Observatory in Gainesville (LOG), Florida. The various factors that can influence electric field measurements are discussed. As an example of application of the system, peak current of a return stroke in lightning triggered using the rocketand-wire technique at Camp Blanding, Florida, was inferred using the corresponding electric field waveform recorded by LDWSS and compared with the directly measured current. Additionally, peak currents inferred from LDWSS field measurements were compared with those reported by the U.S. National Lightning Detection Network. Index Terms-Calibration, electric field antenna, lightning current, lightning detection system, lightning electric field. I. INTRODUCTION T HERE are many processes in cloud and ground lightning flashes, which all have associated with them electric and magnetic fields. Lightning location systems (LLSs) use these electric and magnetic fields to geolocate lightning processes. LLSs are important for a wide variety of applications, such as thunderstorm nowcasting and forecasting, lightning warning, Manuscript

Geophysical Research Letters, 2014

We report on the development of an easily deployable LF near-field interferometric-time of arrival (TOA) 3-D Lightning Mapping Array applied to imaging of entire lightning flashes. An interferometric cross-correlation technique is applied in our system to compute windowed two-sensor time differences with submicrosecond time resolution before TOA is used for source location. Compared to previously reported LF lightning location systems, our system captures many more LF sources. This is due mainly to the improved mapping of continuous lightning processes by using this type of hybrid interferometry/TOA processing method. We show with five station measurements that the array detects and maps different lightning processes, such as stepped and dart leaders, during both in-cloud and cloud-to-ground flashes. Lightning images mapped by our LF system are remarkably similar to those created by VHF mapping systems, which may suggest some special links between LF and VHF emission during lightning processes. LYU ET AL.

Geophysical Research Letters, 2000

In the VHF broad band interferometer, the Fourier transform is applied to analyze the whole frequency range of lightning radiation sources. The position of a radiation source can be determined by resolving the incident angle for each frequency component against at least three-antenna sensors, and then by averaging the incident angles of all frequency components the angular position can be located. This arithmetic-averaging method as proposed by previous authors has a disadvantage, especially for cloud-to-ground flashes, that is positions of lightning leader channels near ground level can not be mapped well. It is found that Fourier spectral amplitudes of broad band pulses decrease with increasing frequency, and frequency components having low spectral amplitudes give less contribution to the lightning mapping. To improve the mapping, a weighted-averaging method is proposed. The method provides a way to minimize the influence of frequency components, which contribute less to the lightning mapping.

Journal of Atmospheric and Solar-Terrestrial Physics, 2002

For the ÿrst time, the broadband radio interferometers have been developed to locate the sources of VHF=UHF radiation from lightning discharges in three spatial dimensions (3D) and time. The lightning observations have been conducted in Darwin, Australia during summer 1998 at two di erent sites. Each site consisted of a broadband interferometer and an electric ÿeld sensor as well as a GPS receiver. The triangulation scheme was proposed to estimate the 3D source locations. The system was able to observe di erent types of lightning discharges and estimate the initial and subsequent leader progression speeds from three negative cloud-to-ground lightning ashes. The initial leaders had progression speeds of about 10 5 m s −1 , typical for negatively charged initial leaders. The preliminary activity prior to the initial leader progression was also recognized. In cloud K-processes, a dart leader and an attempted leader were also found to be negative-polarity discharges and they propagated either upward or downward to ground with the estimated speeds of about 10 6 m s −1 , in agreement with previous studies. Two of the ashes contained subsequent leaders that took di erent channels and created new terminations on ground. These subsequent leaders required long duration to progress downward (about 35 and 65 ms) with the same speed as typical initial leaders before reaching the ground.

2010

Lightning mapping or locating systems are based on several working principles such as the Time of Arrival (ToA) and the Directional Finder (DF). The country wide lightning locating system (LLS) owned by TNB Malaysia is able to determine the coordinate of the cloud-to-ground lightning strike within 500m accuracy. A new method is proposed to determine the coordinate of any cloud-to-ground lightning strike within a certain local region with a better accuracy. The localised LLS is based on the measurement of induced voltages due to lightning strikes in the vicinity of an existing overhead telephone lines. The localised lightning locating system (LLLS) is made up of three components: an overhead telephone line, a voltage surge measuring system, and a central processing station. The overhead telephone line was purposely constructed in such a way to simply form a Cartesian system suitable for lightning strike location mapping. The mapping of the lightning strike locations was successfully implemented using a Lab View based program. Simulated lightning as well as real lightning data were used in this study. The induced voltage waveforms were compared with other previously published data. The location calculations were compared with those obtained from the national LLS. Results show that the LLLS captures more lightning strikes during the period of the study.

2004

Lightning data have been collected by the French Lightning Detection and Location Network FLDLN, the so-called “Météorage” network, over a region situated between 43-45 degrees latitude North and 4-8 degrees longitude East, during the entire year 1999. For more clearness the above mentioned region was marked on the map of France reproduced in figure 1. The area of the observation region can be evaluated to 71150 km. The events recorded by FLDLN are the return strokes in cloud-to-ground flashes. Each event recorded in the database receives an identification number and it is stored with the following attributes: date (year, month, day), time (hour, second), impact coordinates (longitude and latitude), polarity and crest value of the current. If several successive events are identified as return strokes belonging to the same flash each return stroke will receive the same identification number, which will become the identification number of the flash. Figure 1 Position of the observatio...

Journal of Atmospheric Electricity, 2013

Broadband radio interferometers have been developed to locate the sources of VHF/UHF radiation from lightning discharges in three spatial dimensions (3D) and time. The VHF broadband interferometer locates sources of radiation events at VHF band by extracting the differences of phases at various frequency components of Fourier spectra between a pair of antennas. Lightning images are derived by sensing the electromagnetic waves radiated from a lightning discharge process such as negative stepped leader. In this paper, a VHF broadband digital interferometer has been used to estimate the 3D lightning location from only one site. The site consists of three broadband antennas and a GPS receiver. As one of the observation results, a negative downward cloud-to-ground lightning flash will be presented and located using only one site.