Numerical Simulation of Spark Discharges in Air

Plooster, Myron N.

doi:10.1063/1.1693302

Cited by 106 publications

(69 citation statements)

References 15 publications

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“…These energy estimates approximately agree with Plooster's results 28 for a spark discharge in air. Taking into account the loss of energy by radiation, it is reasonable to take the energy at current peak E 0 as an input for driving the shock wave from a lightning discharge.…”

Section: ͑B2͒supporting

confidence: 81%

Bead lightning formation

Ludwig

Saba

2005

Physics of Plasmas

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Formation of beaded structures in triggered lightning discharges is considered in the framework of both magnetohydrodynamic ͑MHD͒ and hydrodynamic instabilities. It is shown that the space periodicity of the structures can be explained in terms of the kink and sausage type instabilities in a cylindrical discharge with anomalous viscosity. In particular, the fast growth rate of the hydrodynamic Rayleigh-Taylor instability, which is driven by the backflow of air into the channel of the decaying return stroke, dominates the initial evolution of perturbations during the decay of the return current. This instability is responsible for a significant enhancement of the anomalous viscosity above the classical level. Eventually, the damping introduced at the current channel edge by the high level of anomalous viscous stresses defines the final length scale of bead lightning. Later, during the continuing current stage of the lightning flash, the MHD pinch instability persists, although with a much smaller growth rate that can be enhanced in a M-component event. The combined effect of these instabilities may explain various aspects of bead lightning.

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Section: ͑B2͒supporting

confidence: 81%

Bead lightning formation

Ludwig

Saba

2005

Physics of Plasmas

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“…All of the first principles line source blast wave solutions were done using numerical results given in Plooster (1968Plooster ( , 1971, which were all originally done for studying lightning …”

Section: Differential Acoustic Efficiency Definitionmentioning

confidence: 99%

Genesis-An artificial, low velocity “meteor” fall and recovery: September 8, 2004

Revelle

Edwards

Sandoval

2005

Meteoritics &Amp; Planetary Science

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Abstract-On September 8, 2004, Genesis, a manmade space capsule, plummeted to Earth after almost three years in space. A ground-based infrasound array was deployed to Wendover, Nevada, to measure the "hypersonic boom" from the reentry, since the expected initial reentry speed of the body was about 11 km/sec. Due to the complete failure of its dual parachute system, we had a unique opportunity to assess the degree of reliability of our previously developed relations for natural meteors and bolides to analyze this well-characterized manmade body. At ∼20-50 km from the nominal trajectory, we succeeded in recording over two minutes of infrasonic signals from Genesis.Here we report on subsequent analyses of these infrasonic data, including an assessment of the expected entry characteristics on the basis of a bolide/meteor/fireball entry model specifically adapted to modeling reentering manmade objects. From these simulations, we were able to evaluate the line source blast wave relaxation radius, the differential acoustic efficiency, etc., to compute an approximate total power balance during entry. Next, we analyzed the detailed signals arriving from Genesis using a numerical, signal detection and wave processing software package (Matseis/ Infra_Tool). We established the initial and subsequent arrivals and evaluated its plane wave back azimuths and elevation arrival angles and the degree of maximum, pair-wise cross-correlation, its power spectrum, spectrogram analysis, standard seismic f-k analysis, etc. From the associated entry parameters, we computed the kinetic energy density conservation properties for the propagating line source blast waves and compared these predictions against observed ground-based infrasound amplitude and wave period data as a function of range. We discovered that previously computed differential acoustic efficiencies were unreliable at Mach numbers below about 10. This is because we had assumed that a line source explosion was applicable, whereas at very low Mach numbers, typical of recovered meteorites, the detailed source characteristics are closer to those of supersonic objects. When corrections for these unphysical, very high efficiencies were made, agreement between theory and observations improved. We also made an assessment for the energy of the blast wave source from the ground-based infrasound data using several other techniques that were also adapted from previous bolide studies. Finally, we made a top-down-bottom-up assessment of the line source wave normals propagating via refraction downward into the complex middle atmospheric environment. This assessment proved to be generally consistent with the digital signal processing analysis and with the observed time delay between the known Genesis reentry and the infrasonic observations.

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“…This value of σ is in the range of plasma conductivities estimated by Plooster [1971] for temperatures above 15000 K and pressures between 1 and 100 atm. An initial channel radius of 1 mm is used, which leads to an initial channel resistance of 12.7 Ω/m that is considered representative of the leader channel resistance [Jayakumar et al, 2006].…”

Section: 1002/2015jd023132mentioning

confidence: 86%

Lightning strikes to tall objects: A study of wave interactions at the return‐stroke front using a nonlinear transmission line model

2015

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A theoretical study is presented to investigate lightning strikes to towers, with focus on wave interactions occurring at the return-stroke front due to the arrival of current pulses that propagate upward on the channel after being transmitted from the tower. The lightning channel is represented as a transmission line including corona and nonlinear losses. Analyses for the hypothetical case of a lossless channel considering matched tower and channel impedances show that the arrival of current pulses at the upward moving return-stroke front leads to an increase in corona currents leaving the channel. This transient process generates current pulses whose arrival at the tower top can be interpreted as the effect of a current reflection at the upward moving front, even though no impedance discontinuity exists at that point if return-stroke and leader channel properties are assumed the same. In the more realistic case of a lossy channel considering unmatched channel and tower impedances, the nonlinear channel resistance modifies the current pulses that propagate along the channel so that they merge smoothly with the return-stroke front. In this case, the interaction of the current pulses transmitted from the tower to the channel with the upward moving return-stroke front does not lead to features that can be clearly interpreted as the result of current reflections at that point in the evaluated conditions. Finally, it is argued that the current reflection coefficient at the tower top should be viewed as a current dependent parameter as opposed to a constant, linear value.

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Numerical Simulation of Spark Discharges in Air

Cited by 106 publications

References 15 publications

Bead lightning formation

Bead lightning formation

Genesis-An artificial, low velocity “meteor” fall and recovery: September 8, 2004

Lightning strikes to tall objects: A study of wave interactions at the return‐stroke front using a nonlinear transmission line model

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