Craig Hayenga - Academia.edu (original) (raw)
Papers by Craig Hayenga
International Astronomical Union Colloquium
Lightning discharges radiate strongly at radio frequencies, and studies of the radiation provide ... more Lightning discharges radiate strongly at radio frequencies, and studies of the radiation provide valuable information on lightning breakdown processes. Interferometric techniques can be used to locate the numerous radiation events as a function of time during a discharge and to generate images of the developing lightning channels inside a storm, where they are obscured from view at optical wavelengths.
The first positions and movement in azimuth and elevation of VHF lightning sources obtained with ... more The first positions and movement in azimuth and elevation of VHF lightning sources obtained with a 34 MHz swept lobe interferometer are presented. The positions are correlated in time with electric field measurements which provide identification of the various processes occurring during a lightning discharge. Data from several flashes are presented. The early or breakdown phase consists primarily of quasicontinuous VHF emission from a large number of linear sources moving rapidly approx. 10 to the 7th power m/s) over distances of approx. 100-1500 meters. The relative positions of these sources drift with a velocity approximately 100,000 m/s. The temporal and spatial patterns of the observed 34 MHz radiation indicate that different processes generate VHF radiation than those that generate lower frequency lightning radio emission. The source of VHF lightning radiation is attributed to the acceleration of electrons in the small high field region at the tip of an advancing breakdown str...
Iau Colloq 131 Radio Interferometry Theory Techniques and Applications, 1991
Journal of Geophysical Research, 1979
We present a new technique for measuring the VHF radio centroid of nearby lightning flashes at 5-... more We present a new technique for measuring the VHF radio centroid of nearby lightning flashes at 5-μs intervals. Its ability to provide continuous positions during long (>˜ 100 μs) emissions is, we believe, new and reveals new information about the discharge process. The new technique solves many of the data-handling problems in old techniques. We have built and demonstrated this technique in one angular coordinate of the lightning flash. We present data from five flashes showing complex positional and motional patterns. The breakdown phase consists of many impulses. The average speed from impulse to impulse lies in the range of 10-100 km s-1. During individual impulses, speeds measure from one to several tens of thousands of kilometers per second. At times of strong VLF bursts there is usually a similar VHF burst. Its speed is like the speeds of individual impulses. We identify VLF-associated VHF burst sources with the main electrical current flow in lightning flashes. We identify the motion from one impulse to another in the breakdown phase as being caused by avalanching electrons accelerating along paths soon to become the discharge paths within thunderclouds. The high speeds in impulses represent the gross current flow in breakdown channels not yet large enough to create large VLF emissions or flashes.
Journal of Geophysical Research, 1981
Using a new radio interferometric technique, we present observations of VHF lightning radiation s... more Using a new radio interferometric technique, we present observations of VHF lightning radiation source positions. The crossed base line interferometer provides the directions of arrival (azimuth and elevation) of VHF lightning radiation. Much flexibility exists in the choice of instrument parameters such as operating frequency and sampling interval. The present instrument operates at 34.3 MHz and provides an average position for every 2.5 μs of lightning radiation. Observations indicate that each 2.5 μs position should be attributed to a single discrete source in the sky. The positions of such sources define the temporal and spatial development of breakdown and rapid charge acceleration during the lightning flash. We have obtained VHF source positions correlated in time with electric field measurements. This allows us to identify the various processes occurring during a discharge and to compare the VHF phenomena with previously observed lightning phenomena. We have analyzed six flashes completely and portions of others. All six flashes contained ground strokes and two had intracloud discharges following the ground flash. We present data from three flashes that showed features common to the flashes we analyzed. The initial (preceding the first return stroke) and intracloud portions consisted of a large number of bursts of 20 μs average duration occurring on the average every 100 μs. The positions within each burst developed in a systematic, nearly linear, sequence with apparent speeds of ˜107 m/s. The relative positions from burst to burst drifted through the sky with speeds ˜105 m/s. In intracloud portions this drift was predominantly horizontal. In ground flashes the VHF sources drifted downward, in effect the leader for the first return stroke. They terminated at the return stroke.
Journal of Geophysical Research, 1981
JC_description.
The potential value of software tools for the modeling and simulation of organization dynamics in... more The potential value of software tools for the modeling and simulation of organization dynamics incorporating individual behaviors in the development, deployment and sustainment of complex systems are considered. Such tools need to provide more value compared to traditional systems engineering and systems of systems tools. Value is the capability to model and assess the effects of small-world behavior in organizations exhibiting complexity. An environmental scan of legacy tools to assess how well they meet these needs is provided. From the assessment of dynamic modeling tools and software, recommendations are derived for software tools. These needs become the requirement set for adequate modeling of organizational dynamics susceptible to individual behaviors
Journal of Geophysical Research, 1979
JC_description.
Journal of Geophysical Research, 1994
A radio interferometer system is described which utilizes multiple baselines to determine the dir... more 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 Geophysical Research, 1994
A radio interferometer system is described which utilizes multiple baselines to determine the dir... more 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. Several modes of breakdown during and after return strokes have been documented and analyzed. 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.
Journal of Geophysical Research, 1984
By using a crossed base line interferometer, lightning VHF source positions correlated in time wi... more By using a crossed base line interferometer, lightning VHF source positions correlated in time with electric field change measurements have been obtained. We present data in this paper showing azimuth and elevation pictures with high time resolution of the VHF (34.3 MHz) radiation for events near the time of return strokes. From their common characteris-
International Astronomical Union Colloquium
Lightning discharges radiate strongly at radio frequencies, and studies of the radiation provide ... more Lightning discharges radiate strongly at radio frequencies, and studies of the radiation provide valuable information on lightning breakdown processes. Interferometric techniques can be used to locate the numerous radiation events as a function of time during a discharge and to generate images of the developing lightning channels inside a storm, where they are obscured from view at optical wavelengths.
The first positions and movement in azimuth and elevation of VHF lightning sources obtained with ... more The first positions and movement in azimuth and elevation of VHF lightning sources obtained with a 34 MHz swept lobe interferometer are presented. The positions are correlated in time with electric field measurements which provide identification of the various processes occurring during a lightning discharge. Data from several flashes are presented. The early or breakdown phase consists primarily of quasicontinuous VHF emission from a large number of linear sources moving rapidly approx. 10 to the 7th power m/s) over distances of approx. 100-1500 meters. The relative positions of these sources drift with a velocity approximately 100,000 m/s. The temporal and spatial patterns of the observed 34 MHz radiation indicate that different processes generate VHF radiation than those that generate lower frequency lightning radio emission. The source of VHF lightning radiation is attributed to the acceleration of electrons in the small high field region at the tip of an advancing breakdown str...
Iau Colloq 131 Radio Interferometry Theory Techniques and Applications, 1991
Journal of Geophysical Research, 1979
We present a new technique for measuring the VHF radio centroid of nearby lightning flashes at 5-... more We present a new technique for measuring the VHF radio centroid of nearby lightning flashes at 5-μs intervals. Its ability to provide continuous positions during long (>˜ 100 μs) emissions is, we believe, new and reveals new information about the discharge process. The new technique solves many of the data-handling problems in old techniques. We have built and demonstrated this technique in one angular coordinate of the lightning flash. We present data from five flashes showing complex positional and motional patterns. The breakdown phase consists of many impulses. The average speed from impulse to impulse lies in the range of 10-100 km s-1. During individual impulses, speeds measure from one to several tens of thousands of kilometers per second. At times of strong VLF bursts there is usually a similar VHF burst. Its speed is like the speeds of individual impulses. We identify VLF-associated VHF burst sources with the main electrical current flow in lightning flashes. We identify the motion from one impulse to another in the breakdown phase as being caused by avalanching electrons accelerating along paths soon to become the discharge paths within thunderclouds. The high speeds in impulses represent the gross current flow in breakdown channels not yet large enough to create large VLF emissions or flashes.
Journal of Geophysical Research, 1981
Using a new radio interferometric technique, we present observations of VHF lightning radiation s... more Using a new radio interferometric technique, we present observations of VHF lightning radiation source positions. The crossed base line interferometer provides the directions of arrival (azimuth and elevation) of VHF lightning radiation. Much flexibility exists in the choice of instrument parameters such as operating frequency and sampling interval. The present instrument operates at 34.3 MHz and provides an average position for every 2.5 μs of lightning radiation. Observations indicate that each 2.5 μs position should be attributed to a single discrete source in the sky. The positions of such sources define the temporal and spatial development of breakdown and rapid charge acceleration during the lightning flash. We have obtained VHF source positions correlated in time with electric field measurements. This allows us to identify the various processes occurring during a discharge and to compare the VHF phenomena with previously observed lightning phenomena. We have analyzed six flashes completely and portions of others. All six flashes contained ground strokes and two had intracloud discharges following the ground flash. We present data from three flashes that showed features common to the flashes we analyzed. The initial (preceding the first return stroke) and intracloud portions consisted of a large number of bursts of 20 μs average duration occurring on the average every 100 μs. The positions within each burst developed in a systematic, nearly linear, sequence with apparent speeds of ˜107 m/s. The relative positions from burst to burst drifted through the sky with speeds ˜105 m/s. In intracloud portions this drift was predominantly horizontal. In ground flashes the VHF sources drifted downward, in effect the leader for the first return stroke. They terminated at the return stroke.
Journal of Geophysical Research, 1981
JC_description.
The potential value of software tools for the modeling and simulation of organization dynamics in... more The potential value of software tools for the modeling and simulation of organization dynamics incorporating individual behaviors in the development, deployment and sustainment of complex systems are considered. Such tools need to provide more value compared to traditional systems engineering and systems of systems tools. Value is the capability to model and assess the effects of small-world behavior in organizations exhibiting complexity. An environmental scan of legacy tools to assess how well they meet these needs is provided. From the assessment of dynamic modeling tools and software, recommendations are derived for software tools. These needs become the requirement set for adequate modeling of organizational dynamics susceptible to individual behaviors
Journal of Geophysical Research, 1979
JC_description.
Journal of Geophysical Research, 1994
A radio interferometer system is described which utilizes multiple baselines to determine the dir... more 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 Geophysical Research, 1994
A radio interferometer system is described which utilizes multiple baselines to determine the dir... more 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. Several modes of breakdown during and after return strokes have been documented and analyzed. 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.
Journal of Geophysical Research, 1984
By using a crossed base line interferometer, lightning VHF source positions correlated in time wi... more By using a crossed base line interferometer, lightning VHF source positions correlated in time with electric field change measurements have been obtained. We present data in this paper showing azimuth and elevation pictures with high time resolution of the VHF (34.3 MHz) radiation for events near the time of return strokes. From their common characteris-