Lightning Phenomena Research Articles

Great balls of what?

Philip Ball reports on new claims that the strange phenomenon of ball lightning is simply a kind of glowing candy floss spun from earth.

Middle atmospheric electrodynamics at low lattitude over India

Low latitude middle atmospheric electrodynamics has a number of interesting features such as low flux of cosmic rays due to high cut-off rigidities, higher solar electromagnetic radiation intensities and mesospheric ionisation, large scale convection and wide-spread lightning phenomena, higher tropopause level and special characteristics associated with the equatorial electrojet. These special features play a vital role in governing the electrodynamics of the global middle atmosphere. In India, a well coordinated multi-institutional campaign was organised under MAP (Middle Atmosphere Programme) to carry out balloon and rocket borne experiments to measure electrical parameters of the middle atmosphere. The measured parameters include electron/ion densities and mobilities, polar ion conductivities and electric fields. The experiments were carried out during different seasons and solar activity epochs. The results obtained from these investigations are discussed and compared with similar measurements over the middle latitude stations to assess the integrated effect of the global atmospheric electrodynamic phenomenon.

Radio interferometric observations of cloud‐to‐ground lightning phenomena in Florida

Radio frequency observations of cloud‐to‐ground lightning in Florida have been analyzed to document a number of features of the lightning. The observations have been made using an interferometer system which determined the direction to the lightning radiation as a function of time during close lightning discharges. Observations are presented for about 50 radiating events during five multiple‐stroke, normal‐polarity flashes to ground. The results confirm and extend results of a similar study of New Mexico lightning by Rhodes et al. (1994). Dart leaders, in‐cloud “K” events, and attempted leaders are found to be the same phenomena, namely, a negative‐polarity streamer that propagates horizontally and/or vertically to ground at estimated speeds of about 107 ms−1 down to 106 ms−1. The step or impulsive fast electric field change produced by some K events is found to be caused by positive breakdown back at the starting point of the negative streamer, after the streamer has progressed over some or all of its distance. This breakdown appears to initiate a “forward” stroke along the streamer channel which can renew the breakdown at the front end of the channel. K breakdown which happens to occur during a continuing current discharge to ground produces an M event (channel brightening) when it connects with the conducting channel to ground. The step fast field change of the M events is found to be produced at the time of connection inside the cloud; no fast field change is detected when this breakdown reaches ground that would be associated with a return stroke. M events can also be initiated by fast (107 ms−1) positive streamers which often propagate away from the leader source region within a few milliseconds of the arrival of a return stroke back in the source region. These streamers often generate an even faster negative recoil event back along their extent which propagates down the channel to ground, as the M event. In all cases the current increase or channel brightening produced by K and M events is predicted to occur in a forward direction, that is, toward or down the channel to ground, in the same direction as the initiating negative streamer. Positive breakdown is detected only immediately following return strokes or during some K streamers. In both cases the electric stresses are expected to be very large, suggesting that positive breakdown which produces a conducting channel is difficult to initiate. Results for one flash suggest that negative charge was left at low altitude by the initial stroke to ground; this forced the subsequent leaders to develop a new path to ground, first as series of attempted leaders and then as a dart‐stepped leader.

Dual Polarization Radar Observations of Thunderclouds in Winter Season.

The authors investigate the characteristics of thunderclouds associated with lightning phenomena in the winter season using the dual polarization Doppler radar of the Ministry of Construction known as the DND (Dobokuken-Nijuhenpa-Doppler) radar. This paper deals with the discrimination between different types of precipitation particles and presents the relationship between the movement of the particles and lightning processes. Our results suggest that the dual polarization observational mode, detecting both the horizontal radar reflectivity factor (ZH) and the differential reflectivity factor (ZDR), may discriminate between precipitation particles such as graupel or ice crystals, and that the observed radar echoes indicate a close relationship between the contact of these precipitation particles and the lightning process. Also, simultaneous field-mill observations suggest that graupel has negative charge while ice crystals have positive charge in thunderclouds. This electrical phenomenon is well described in terms of recent thunderstorm electrification theories at temperatures below -10°C.

Electrical safety: a guide to the causes and prevention of electrical hazards

* Chapter 1: Physiological effects of electric current * Chapter 2: Electric power systems * Chapter 3: The philosophies of earthing * Chapter 4: Cables and fires * Chapter 5: Electrical equipment for use in explosive atmospheres * Chapter 6: Protection by flameproof enclosure * Chapter 7: Protection by intrinsic safety * Chapter 8: Electrical apparatus in areas subject to flammable dusts * Chapter 9: Design, workmanship and maintenance * Chapter 10: Stored energy * Chapter 11: Electric welding * Chapter 12: Lightning phenomena and protection * Chapter 13: Coping with static * Chapter 14: Electromagnetic radiation * Chapter 15: Earth currents and their effects

Lightning research: where do we go from here?

The paper was presented as the keynote address to the First All Africa International Symposium on Lightning, co-sponsored by the Zimbabwe Institution of Engineers and the IEE. Thunderstorm activity in most of tropical Africa greatly exceeds that in industrialised countries, and lightning thus becomes a special problem for the tropical areas of the developing world of today. While research over the past years has produced many statistics, facts and theories concerning lightning phenomena, which are reviewed in the paper, it also reveals many gaps and unknowns which must be taken account of in interpreting existing data. This leads finally to what in the author's opinion are the priorities for future lightning research especially in the context of Africa.

新しい雷放電進展モデルの検討

Lightning is one of the most important reasons for proper insulation design of power transmission apparatus. It has been known that lightning progression features in winter and summer seasons differ in the occurrence process and a scale and so on. There are unknown lightning parameters though a lot of records of lightning observation were obtained up to this time.This report deals with a new lightning progression model and the estimation methods of the various parameters of the lightning phenomena quantitatively based on the data of long gap tests and lightning observations. The new progression model is applicable to not only winter lightning but also summer lightning, and the values of various parameters such as the charge density of a stepped leader, the leader development velocity, the time interval between steps, the time-to-discharge of first stroke, the final striking distance and so on are estimated by a new calculation method. The new model is useful for a computer simulation of lightning progression and development of a new lightning shielding theory.

Eddy current model of ball lightning

Eddy Current Model of Ball Lightning Calculations show that high-energy ball lightning may consist of a ball of plasma containing a large circular electric current arising as an eddy current generated by lightning. Synthetic ball lightning might serve as a method of plasma confinement for purposes of nuclear fusion. In this paper, three articles concerning ball lightning and the related phenomenon of large ball lightning are combined to provide insight into this rarely glimpsed occurrence.

An electrostatic-chemical model of ball lightning

We give a brief description of the ball lightning phenomenon and list the properties of the average fireball based on the available data. We then discuss briefly a recent theory to account for the data.

The role of electric space charge in nuclear lightning

The phenomenon of nuclear lightning is reexamined with theoretical models and laboratory‐scale experiments. It is shown that the distribution of electric space charge, rather than the electric field alone, must be considered in accounting for the shapes and locations of nuclear lightning channels in the atmosphere. A self‐consistent distribution of space charge requires a consideration of both electronic and ionic conduction in the irradiated atmosphere, in agreement with earlier findings (Grover, 1980). The magnitudes of nuclear lightning currents (105–106 A) (Colvin et al., 1987) are compatible with predictions for electrical conduction currents based on contemporary theory. Comparisons between the theoretical predictions and laboratory discharge experiments for the nuclear lightning case emphasize the dominant influence of electric space charge on discharge paths in both solid insulators and thunderclouds.

Melville on Science: "The Lightning-Rod Man"

A MAJORITY of critics have viewed the title character of Melville's The Lightning-Rod Man (1854) as a symbol of evangelical Christianity,' and one can easily see why. He not only accuses the unreceptive narrator of profanity and infidelity2 but also has the habit of incorporating biblical language into his sales pitch. Mine is the only true rod, he soberly maintains (p. 277). There is a problem, however, in treating Melville's lightning-king as an allegorical peddler of religion, for rather than relying chiefly upon pious accusations and scriptural allusions, the lightning-rod man typically fills his conversation with technical assertions regarding the phenomenon of lightning and the practical precautions most helpful in avoiding its dangers. In an allegorical assault on hard-core Protestantism, such remarks various and continual -would seem curiously out of place. Perhaps those critics who have dubbed the salesman religious, minimizing his obsession with matters of electricity, should reconsider the question of who that salesman is. One significant clue to his allegorical identity is a probable Melvilleian source-Benjamin Franklin's Letters and Papers

The Response of a Transmission Line Illuminated by Lightning-Induced Electromagnetic Fields

This paper presents the theory and procedures used to estimate the voltages and currents induced on long transmission lines by cloud-to-cloud lightning. A model for cloud-to-cloud lightning phenomena is presented, and the theory necessary to calculate the electromagnetic fields created by the lightning stroke is derived. The time-domain transmission-line equations in the presence of external electromagnetic fields are presented. A time-domain formulation is more convenient if, in the future, nonlinear effects are to be included. The results of sample calculations, using finite-difference techniques for the solution of the transmission-line equations, are presented.

Spectral intensities emitted by lightning discharges

Peak spectral intensities emitted by seven types of lightning phenomena, viz., first and subsequent return strokes, stepped and dart leaders, cloud-to-air flashes, intracloud pulses, and M components of return strokes, are reported in five narrow regions of the visible and near-visible spectrum. At 3914 A the peak continuum radiation varies from 300 to 107 watts ster−1 A−1, averaged over a 23-A bandwidth and integrated over the whole source. For the average lightning stroke, the spectral intensities at the other regions studied, relative to that near 3914 A, are: 0.95 at 4140 A (continuum), 2.1 at 6563 A (Hα plus continuum), 4.8 at 8220 A (NI[2] plus continuum), and 0.7 at 8900 A (continuum). Return strokes are usually the most intense lightning phenomena but can vary in intensity by a factor of 1000 from storm to storm and by a factor of 50 within one flash. The most intense return strokes appear to have the highest radiating temperature. Stepped and dart leaders are a factor of 20 to 100 less intense than their return strokes, but the leaders and return strokes have similar spectra. Pulses originating within clouds vary in intensity from the weakest pulses observed to ∼105 watts ster−1 A−1 near 3914 A and are substantially stronger in the near-infrared channels, relative to the 3914-A channel, than the average stroke. M-component brightenings of return-stroke channels are of lower excitation than typical return strokes but are otherwise similar to them. There is no indication in any of these strokes of the strong N2+ 1N (3914 A) radiation present in some slit spectrograms in the literature.

Time interval between lightning strokes and the initiation of dart leaders

The temperature decay of a lightning channel during the interstroke period is determined theoretically. It is shown that, in the absence of input energy to the channel, the channel temperature will decay sufficiently slowly so that conditions conducive to the initiation and propagation of a dart leader will exist in the channel after a typical interstroke period of 40 msec. Thus, it would appear unnecessary to invoke the special mechanisms suggested by Brook et al. and by Loeb to explain the ‘long’ interstroke period. The calculations indicate that the lightning channel radius during the latter stages of a lightning stroke is of the order of centimeters. A mechanism is suggested to explain the phenomenon of bead lightning and to account for the observed long-lasting luminosity occurring at certain points on the normal discharge channel.

A theory of ball lightning

A mathematical theory of ball lightning is presented. Ball lightning is considered to be an externally powered dc phenomenon that results from the funneling of cloud-to-ground current through a region of high temperature and high electrical conductivity. An approximate solution of the equations of current conservation and energy conservation with proper boundary conditions yields a luminous region of air. The predicted ball lightning diameters are in good agreement with observation for reasonable values of current, current density, electric field, and electrical conductivity inside and outside the ball. The luminosity, energy content, formation, locale, motion, and observed modes of disappearance of ball lightning are discussed. An explanation for the phenomenon of bead lightning is advanced.

Field Mapping Techniques for Lightning Protection

The lightning mast and overhead ground wire are well-established methods for protecting structures from direct lightning strokes. The advent of space vehicles and missiles with stored or contained propellants, and the exposure of extremely sensitive circuitry, compel the design engineer to investigate the degree of lightning hazard and to inquire into the margin of safety provided by these conventional methods of protection. Field mapping techniques and field equation analysis are powerful tools for such investigations. This paper presents a condensed discussion of basic lightning phenomena, field mapping methods for determining the pre-strike field conditions, and a field equation analysis of the transition from the static to the dynamic state. This analysis is provided for the pre-strike period, the lightning stroke and follow-through period, and is continued until static field conditions are restored.

Bead lightning and the pinch effect

A new explanation for the phenomenon of bead lightning is proposed. Under special conditions the pinch effect generates radial modulation periodically along the lightning column. The radial modulation causes the lightning column to deform into a “string of sausages.” The strongly pinched regions are visually very bright; the weakly pinched regions appear dark in comparison.

On the Question of Ball Lightning

The hypothetical model of ball lightning first suggested by P. L. Kapitza [Doklady Akad. Nauk S.S.S.R. 101, No. 2, 245 (1955)] is considered in some detail in an attempt to uncover evidence which will substantiate or contradict the theory. Observers' reports of the phenomenon are summarized briefly. Pro and con arguments concerning Kapitza's scheme are given. A theoretical model in an ideal environment is examined. The radio-frequency field suggested by Kapitza is considered, and the interference effects resulting from the reflection of a discrete band spectrum of linearly polarized waves from a perfect reflector are presented. The gaseous discharge is discussed, under the assumption that the ball lightning phenomenon is analogous to a point-to-plane corona discharge. It is determined that, given a sufficiently intense electric field, a horizontal discharge along one of the electric field antinodes, suggestive of horizontal lightning, can result. It is concluded that this exploratory work supports Kapitza's hypothesis, but that much more must be done before the theory is fully substantiated.

Thunderstorm electrical discharges intercepted by aircraft and related ball lightning and sferics phenomena

Continuing records of pitting and denting effects of lightning strikes to aircraft, checked by laboratory artificial lightning currents, indicate frequent transfers of more than 200 coulombs in the intercepted discharges. There have been some pilot's reports of occurrence of ‘ball lightning’ for a number of the strokes, some of which are being studied and set up for reproduction in laboratory experiments. Related sferics have been studied and discussed in relation to interference effects on aircraft radio and also in possible application of their location as an aid in thunderstorm avoidance by aircraft. Some laboratory experiments on duplication of the lightning discharge channel have been carried out which checked closely with aircraft-intercepted lightning.

Analytical Studies on Lightning Phenomena Involving Towers, Insulator Strings, and Transmission Lines

Analytical Studies on Lightning Phenomena Involving Towers, Insulator Strings, and Transmission Lines