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May be that it is thundering during the whole night. The program displays several topics when the following items are selected: All items: from Processes of charge separation to Relation to the ionosphere. Processes of charge separation: from Charging process in the liquid phase to Final distribution of charges. Charging theorises: from Charging process in the liquid phase to Charging process during freezing. Processes of charge separation Charging process in the liquid phase At the base of a thunderstorm cloud, the temperature is above the freezing point and therefore it consists of water drops.

These different physical conditions lead to several processes of charge separation. Wind blows under the cloud and then turns upwards. Inside the cloud, a cold front can produce intensive wind, which is often upward directed. This phenomenon is called waterfall electrification. Lenard explained the mechanism of waterfall electrification using the droplet fragmentation theory. Later G. Simpson applied this theory to describe the electrification in the liquid zone of thunderstorm clouds. The ionosphere produces an electric field that separates the positive and negative electric charges so that the bubble becomes negative and the flange below becomes positive.

As a consequence of this process, the positive and the negative charges are separated inside the cloud. Charging process during freezing In the upper part of a thunderstorm cloud, the temperature is below the freezing point and therefore the water drops begin to freeze. This process does not proceed in one step, but first supercooled water drops and ice particles are created. There are many electrification processes associated with freezing, but many are not sufficiently effective to produce a charge that is large enough compared to the recorded values.

The mechanism according to the theory by B. Mason and C. Latham seems to be sufficiently intensive for producing the amount of charge that corresponds to the observations. When the freezing progresses towards the inside of the drop, this ice shell becomes too restricted for the expanding new ice core and therefore the outer ice layer cracks. The heavier ice grains do not go so high, and they spread their negative charge in the middle zone of the cloud.

The ice grains and the sprayed water droplets fill the middle zone of the cloud with a large negative charge. As a result of the charge separation in the liquid and in the ice phases, the indicated three pole charge distribution is created in the typical thunderstorm clouds. Final distribution of charges As a result of the charge separation in the liquid and in the ice phases, a three pole charge distribution is formed in a typical thunderstorm cell, as shown in this picture.

The greatest amount of electric charge is at the top and in the freezing region. Although the lower positive centre is considerably smaller, it is also important because no rain falls usually in this place and so enhanced danger threatens people in open air. Such a model has been created by G. Simpson, who assumed uniformly charged spheres of different sizes and centres at different heights, as shown in this picture.

The lower positive centre does not reverse the field but decreases it a little. The large positive charge on top of the cloud produces a high upward-directed field strength. Although the positive flashes usually carry a higher charge, the lower frequency of their occurrence cannot balance the asymmetry of the polarity of ground flashes.

Therefore, a surplus of positive charge remains in the cloud. This charge produces a high upward-directed field gradient above the cloud. The thunderstorm clouds form a global generator, which transforms thermal energy of the atmosphere into electrical energy and charges up the ionosphere with positive ions. In regions of clear weather, this field drives positive ions downwards, which forms the fine weather current.

Plotting this against Greenwich Mean Time GMT the regions of highest isokeraunic levels cause peaks in the early afternoon. This is also related to the daily distribution of thunderstorms. This supports the theory that a relation exists between the ionosphere and the thunderstorms.

The program displays several topics when the following items are selected: All items: from Photon processes to Klydonograph and pictures. Photon processes: to Ionisation and recombination. Electron collisions: to Ionisation by collision. Discharges: from Electron avalanche to Klydonograph and pictures. Streamer discharge Klydonograph and pictures. Photon processes Lightning flash is an electrical discharge in the atmosphere. It is useful to study the physics of discharges in air. There are some other phenomena whose interpretation also requires an understanding of gas discharges.

A gas discharge is often connected to photon processes. The energy of the visible radiation increases from red to violet, and is considerably higher in the case of ultraviolet, X-ray or radioactive radiations. If its energy is high enough, the photon can affect the atoms and molecules of the air. Excitation by photon Electrons of the atoms and molecules can have discrete energy levels. To raise the energy of an electron from the ground level to a higher level, energy of excitation Wg is required, which is a property of the atom or molecule.

If the energy of a photon is high enough, it can cause excitation in case of collision. The atom does not remain in the excited state, but the electron returns to the ground level, and the atom emits a photon of excitation energy. If the energy of a photon is high enough, it can ionise the atom or molecule in case of collision. This process produces a free electron in the air, which moves away.

There are certain electro-negative gases in which the external electron shell is not closed, and these can absorb electrons. If the kinetic energy of a free electron is less then Wa, it will form a negative ion with an oxygen molecule. Therefore, free electrons exist for only very short periods in the air. Recombination In fine weather, 5—6 ionisations happen in each cubic centimetre of air, producing both positive and negative ions. However, their number cannot grow limitless because the ions of opposite polarities attract and after contact neutralise each other.

Since the positive ion strongly attracts the negative electron, the electron approaches it with a high velocity. The electron gains very high kinetic energy and therefore the ion cannot trap it. If the electron does not approach the ion along a straight line towards the centre, it travels beside the ion along a path similar to that of a spaceship beside a planet e. Therefore, the recombination of electrons and ions almost never occurs. Electron collisions If a free electron is subjected to an electric field, a force F affects it, which is proportional to the charge qe 1.

Because of the negative charge of the electron, this force acts in an opposite direction to the gradient. This energy can be finally expressed by the potential difference Ux — Uo between the origin and the end of the free path. If this is not high enough to affect the molecule, nothing will happen and the electron springs off without any interaction. Excitation by electron If the kinetic energy We, collected by the electron along the free path x, exceeds that, which is necessary to cause excitation, the molecule achieves an excited state. The electron will lose its kinetic energy on collision and its acceleration starts once again on the next free orbit.

The molecule then emits the energy of excitation as a photon. Ionisation by collision If the kinetic energy We, collected by the electron along the free path x exceeds that, which is necessary to cause ionisation, another electron escapes from the molecule. The first electron loses its kinetic energy on collision, but the acceleration begins once again. After an ionisation process, two electrons drift in the electric field and both can cause excitations or ionisations on further collisions.

The free path required to cause ionisation is called the path length of ionisation. Discharges Electron avalanche When an electron moves under the influence of an electric field, collisions may occur with the molecules of air. Between two collisions, the free paths have different lengths and so they cause different effects. Sometimes, ionisation occurs and an additional electron is released. Other collisions cause excitations but some of them have no effect.

The increase dn is proportional to the number n x of the arriving electrons and the length dx. The positive and negative charges distort the potential and at the front of the avalanche the gradient E increases rapidly. Raether in a Wilson cloud chamber in The cathode negative electrode is on the left and the avalanche propagates against the anode positive electrode on the right. Along the path of the electrons the saturated steam condenses and produces the shape of the avalanche [20] Streamer discharge At the front of the avalanche, the enhanced electric field gradient E causes intensive collisions that produce many photons of high energy.

These travel at the speed of light and result in ionisation at all points ahead of the avalanche. These free electrons soon accelerate and form secondary avalanches, which immediately begin to propagate. Later, the positive and negative charges of the secondary avalanches make contact and finally join the secondary avalanches. The property of the discharge changes and the avalanche is transformed into a streamer discharge.

This transformation usually occurs after propagating avalanches of 1—2 cm in length, when a longer streamer discharge develops. In addition to the ionisation by collision with electrons, the ionisation by photons also occurs. The corona discharge may consist of electron avalanches just beginning and extending to a few millimetres.

The discharge in the photograph is larger and consists of streamer filaments that continuously move and merge into diffuse light. The St. Elmo fire is assumed to be identical to the corona discharge, although it is probably of another type, which propagates into a space charge region from high- pointed structures such as the towers of the St.

Elmo church, which is located on the coast. Klydonograph A special form of streamer discharge can be seen in a device called a klydonograph. It was used to record lightning at the beginning of the 20th century. In this device, a pointed electrode is positioned at a short distance above a photo- plate or film. These are placed on a metal plate. The pointed electrode is energised but the plate is electrically floating.


After development of the photo-plate or film, a specific image is obtained. The different shapes characteristically verify that the polarities and the diameters are related to the voltages that produced them. While the avalanche is propagating, the current increases at the point of initiation. This graph illustrates in green the change of current on top and change of potential at the bottom, which is distorted by the avalanche.

Ahead of streamer, the graph illustrates the change of potential in green. If the gradient is high enough here, the discharge can propagate forward. When the streamer current exceeds the threshold of thermal ionisation the process will change again. The streamer propagates forward until the gradient at its leading head is steep enough or the current exceeds the threshold of thermal ionisation. In this type of discharge, the ionisation by collision of electrons is negligible and the thermal ionisation becomes dominant. The positive streamer continues in fine filaments on the lower part of the picture.

Against the negative discharge, upward streamers rose from the plate. Some streamers came in contact with each other and they began to form leader channels. The program displays several topics when the following items are selected: All processes: from Start on drops in the cloud to Real Boys records. From leader to main stroke: from Downward leader to Upward leader.

The Boys camera: from Invention and construction to Real Boys records. Striking process: a section from Boys record of ideal lightning. Start on drops in the cloud Inside thunderstorm clouds, turbulent winds drive electrically charged water drops up and down.

PUBLIC LECTURE : Basics of Lightning Protection & Surge Protection Systems

These produce high electric fields but a discharge can only originate from an electrode, in this case the water drop. Although there are no direct observations available concerning this process, the first discharge probably starts as depicted by the mechanism shown in the next pictures. The drop as a conductive sphere modifies the field so that it increases to 3Eo at two points.

The field strength separates the opposite charges inside the drop. Because the drop is not a solid body, the electrical forces can easily distort it and the ends of the drop become increasingly pointed. The field gradient gets enhanced at these points and a corona discharge is initiated, which eventually develops into a streamer state. The current associated with this discharge heats the drop at the contact spots and the water begins to evaporate.

These streamers disappear without an electrode, but they may reappear in large numbers, eventually recombining to form a discharge. Although many of these will also disappear, some may persist leading to a low probability of the growth of a discharge. These persistent discharges produce electromagnetic waves that have been recorded by lightning detection systems. Nevertheless, one of these discharges may grow and develop out of the cloud with low probability. This is the first phase of a lightning flash.

From leader to main stroke A long discharge, which can grow out of the cloud, is transformed into a leader type: at least in the core of its channel. The voltage drop is low along the leader channel and therefore it can be assumed to be a conductive channel, similar to a piece of wire. At the ends of this channel, the gradient of the electric field is high enough to create conditions conducive to forward propagation.

The downward leader travels in the upper section along a zigzag path, with side branches occurring sometimes. Propagation will not be continuous, but will be step-like. This is referred to as a stepped leader. When the downward leader approaches the earth, connecting leaders originate from the earth structures and eventually meet the downward leader. As the conductivity of the earth is considerably higher than that of the cloud, a discharge of high current occurs branching off in the cloud so as to neutralise the opposite charges.

This is the main stroke of the lightning, which always moves upwards and therefore is called return stroke. At the junction, this very bright discharge penetrates into the branches, and is also illuminated. Two of the leaders are easy to identify, which are 1.

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The third leader meanders behind the main channel up to 2. Their development is broken when, the main stroke is initiated by another the fourth connecting leader [15]. The cloud usually covers this section of the lightning but the branches can be seen in this picture. Such a photo is very rare. On the lower part of the lightning path, a branch verifies that the downward leader introduced this stroke [19]. Usually, one of these strokes will be dominant.

In the middle, the lightning channel branches off at a short height, at sometimes 10 m above the earth. On the right, the branching was higher up and alongside the bright main channel is another weak branch. Multiple stroke This is the process leading from the stepped leader to the main stroke, as shown before. While propagating forwards, the stroke is repeated, but other physical processes are also responsible for this mechanism. This is the dart leader, which continuously runs down and illuminates m long sections of the channel.

The dart leader starts connecting leaders from the earth, in a manner similar to the stepped leader. This is followed by one or more subsequent strokes. In between the multiple strokes, relative long periods of flashing may be seen by the naked eye. Sometimes the paths of subsequent strokes will diverge. The physical parameters of the first and the subsequent strokes differ considerably from each other. Upward leader On the top of high structures, the electric field is intensified to initiate a leader that propagates upwards.

It is analogous to a connecting leader produced by the charges of the cloud, or by a downward leader, which is hidden in the cloud. The step-like propagation is not characteristic at the upward leader and its branching differs considerably to that of a downward leader.

Its physical parameters are, however, very different. The path branches at sharp angles and does not deviate much from the vertical [2]. The shape of some branches is almost rectangular, with paths turning upwards. Some branches move very far horizontally, which demonstrates that the main stroke occasionally neutralises the charges in the neighbouring thunderstorm cells.

It is possible that a multiple stroke was photographed. On very high structures, the proportion of upward leaders becomes dominant. The Boys camera: principle and construction The Boys camera is a special device used to record the development of lightning. The lightning flash is such a rapid phenomenon that its development cannot be seen without the use of special recording equipment. The human eye at best can only observe the flash of multiple strokes. This may be recorded accidentally when lightning is photographed with a hand-held camera.

In this case, the camera usually moves, and so the image of the lightning will be shifted, although the lightning propagates along the same path. If the camera continuously moves during the subsequent strokes, then each stroke will appear on the photograph as well. This picture was taken with an amateur camera at Lake Balaton 10 years ago.

Either the motion of the camera or the wind caused a shift of the path images. This figure indicated the phases of the lightning development, which led to the invention of the Boys camera.

Understanding Lightning and Lightning Protection: A Multimedia Teaching Guide

Boys began to develop his camera in the beginning of the 20th century, and according to one of his letters, he made the first successful record in In the following 10 years, many Boys records were made, which eventually made possible the recording of the finer details of the lightning mechanism [2]. However, it was very sensitive to accurate adjustment and the records could only be evaluated with great difficulty. The picture shows an advanced type of camera, which has only one lens. The film runs behind the lens inside the shell of a rotating drum. This can be seen in front of the device.

Another camera simultaneously records a static photo of the same lightning [16]. While the spot moves downwards, its track is shifted to right on the film. It can therefore be taken that time progresses to the right on the Boys record. The motion of the bright spot was seen in the blue field on the right side. Therefore, the track of the spot will also be shifted to right on the film, while the spot moves upwards.

It can therefore be generally stated that: Images on the right of the Boys record indicate later events in any particular sequence as before. As result, a white trapeze shape appears on the photograph.

Prof. Tibor Horváth - ICLP Centre

Therefore, a line on the film corresponds to a moving spot, while an area indicates a growing channel. Boys record of ideal lightning Assuming the ideal lightning channel as a vertical line, this picture would be obtained on the Boys record. When the lightning has a zigzag path, it can be transformed to this form using a still picture, although it is a difficult procedure.

Progressing the program will show each phase of the lightning process that can be evaluated from a Boys record [21]. This form and the inclination indicate that a bright spot moved downwards, and finally disappeared after a short period of flashing. The then process remained static for a relatively long time. The next line is far right of the photograph and starts from the same height as the termination of the previous line. This is a stepped leader, whose steps run very rapidly, as it is evident from their length and their duration. After contact with the downward leader, the main stroke begins and propagates upwards.

This phase of the process will be shown in the next picture. The main stroke propagates first up and down from the contact point of the leaders, but then its inclination and the bright area demonstrate that it is an upward growing channel whose light slowly becomes dark. The dart leader draws a continuous line that differs considerably from the stepped leader, but the subsequent stroke is similar to the first main stroke. This picture indicates these pauses on a distorted scale.

Real Boys records This is an old Boys record made in the early s. In the middle, is a static picture that shows the real path of the lightning. The Boys picture rotates, and because of this, the details appear to overlap. The first stroke is at the bottom and six subsequent strokes can be seen at the top [16]. Berger generated many Boys records over a period of 20 years.

This is a static photo of a curious flash, which struck the side of a 70 m high tower at a point 15 m below the top. Some Boys records of the same lightning will be shown in the next pictures [2]. It indicates the downward moving stepped leader and the first main stroke. Some sections of the branching channel can be also seen among the steps. This record is very similar to that of an ideal lightning. In contrast with the first stroke, the branching channel did not flash all over again. It is only a thin line on the picture, because the dart leader is visible only for a very short time.

It is not typical for the channel to flash repeatedly along the entire length during the stepwise propagation. This leader was interrupted before it developed into a main stroke. However, its intensity was not sufficient to produce an image on the photographic film. The program displays several topics when the following items are selected: All items: from Properties of downward leader to Distribution functions. The main stroke: from Development of main stroke to Lightning parameters.

Lightning parameters: to Distribution functions Properties of a downward leader The downward leader brings charge from the cloud and distributes it along the channel. In this case, it is assumed as negative. The specific density of charge q z increases downwards and reaches the highest value at the head of the leader. This charge produces an electric field at the ground surface, whose gradient Eo is directed upwards when the leader channel is negative. High gradients exist only near the head of the leader. This high field determines the direction of propagation of the leader, which is not influenced by the structures on the earth.

Near the ground surface, the electric field can be assumed homogeneous with a constant gradient Eo that increases proportionally to the specific charge q of the leader channel. Thus, the field strength Eo is also a function of the height z of the head of the leader. This is a leader type in which intensive thermal ionisation exists. Around this thin core is a high radial electric field that produces a corona discharge. The corona extends to a distance where the field gradient is no longer high enough to cause ionisation by electron collision.

The corona envelope has a surprisingly large diameter and stores high amount of charge. Condition of connecting leader A connecting leader can start from a structure on the earth if the field is intensive enough at its top to produce the required conditions. But it does not mean that a pointed rod could force the initiation of a connecting leader, because a corona discharge will be created and its space charge would inhibit the development of a leader channel.

There is consequently no reason to use pointed lightning rods, as was originally thought. Pointed electrodes enhance the field strength over only a small distance, and are therefore not effective. A far extending average gradient is mainly influenced by the height of a structure, which can sufficiently distort the field Eo. The un-distorted field must reach a critical value Ecrit in order to create the initiating condition of the connecting leader.

A connecting leader starts only if the field strength Eo, due to the approaching leader, is higher than Ecrit, depending of the height of the structure. Therefore, the downward leader only needs to produce a lower field gradient Eo to excite a connecting leader. Using the earlier found equations, a relation can be defined between this height, the charge q of leader and the height h of the earth structure.

These produce a high electric field and therefore a very high energy collision begins. Striking process The collision of negative and positive charges heats up the channel and it leads to intensive thermal ionisation. As a consequence, hot plasma begins to extend upwards and towards the earth as well. In this case, positive charges move upwards and neutralise the negative charges of the leader channel.

The upward moving electric charges represent a current that corresponds to the rate of change of charge. After some transformation, this current i becomes a function of the specific charge q stored in the leader channel. The critical height zcrit can be finally expressed by the lightning current. Development of main stroke Assuming that the downward leader started from a negative centre of the cloud, its core will be enclosed by a negative corona envelope. This has a diameter of 5—10 m. Within the core, thermal ionisation probably occurs, which can contribute some hundred amperes of flowing current.

During this process, a new section of the plasma channel is heated up and the main stroke propagates further. A high current flows in the plasma channel and it creates a magnetic field around itself. This magnetic force compresses the channel to a diameter of 50— mm. The temperature increases to 30 K, which is much higher than that of the sun K. Following this, an ionised channel remains along the path of the main stroke. These further neutralise the consecutive centres of charge. The subsequent stroke usually propagates faster but its duration is shorter than that of the first stroke.

The shape of the current impulse is shorter than in the case of the first stroke, but multiple strokes produce the highest rate of rise of current. Dart leaders and subsequent strokes: See: Development of the lightning flash Multiple stroke. It requires conditions similar to a connecting leader but no downward leader can be observed, because it either is hidden in the cloud or does not exist at all. Then a main stroke propagates upwards along each branch of the channel. Inside the cloud, several charge centres will be neutralised by the opposite charge coming from the earth.

In contrast to stroke initiated by a downward leader, in this case the collision of opposite charges occurs far from the striking point. Therefore, the lightning current does not suddenly rise but the current wave increases slowly. The current wave When a downward leader initiates lightning, the current of the first stroke is an impulse.

The subsequent strokes also produce impulses whose duration is shorter than that of the first. The peak values of the impulses are a minimum 1 kA but several kA may also be produced. Sometimes a continuous current flows between the impulses, but it will generally only be in the hundred ampere range. The front of the wave changes very rapidly and the oscillograms often record oscillations at the peak value or at the beginning. Therefore, the front time is defined as shown in the picture. The time to half value extends from the beginning to the time when the decreasing wave reaches half of its peak value.

This time value characterises the duration of the impulse. The picture shows two typical waves recorded at the point of strike. The typical positive waves increase slowly but their duration is long relative to the negative waves. The delay of the peak value may be due to the influence of the measuring system located on the top of a high tower.

The time to half value is also considerably shorter in the case of the subsequent stroke compared to that of the first. All time values are shorter than for positive waves. During the first section, the current increases at the point of initiation because the leader becomes longer and usually branches. When it reaches a charge centre in the cloud, the neutralisation begins but this causes no immediate influence on the earth. The high resistance of the long lightning channel also impedes the rise of the current; therefore, a rapid change cannot occur and the peak value of the current is statistically lower than that of strokes introduced with downward leaders.

Lightning parameters The statistical distribution is the probability that the lightning current is higher than the value of abscissa. It is plotted in this special coordinate system by a straight line that corresponds to a logarithmic normal distribution. In every second case, the peak value of the positive current wave exceeds 36 kA and that of the negative first stroke 32 kA. In the case of subsequent strokes, the median is considerably lower. Extremely high positive currents occur with a higher probability than negative currents [1, 3] statistical distribution: See: Idem Distribution functions.

Its probability of occurrence can be described with a logarithmic normal distribution; therefore, it is plotted by a straight line in this special coordinate system. From the point of view of lightning protection practice, the highest values are interesting. According to this diagram, the highest values occur in the case of negative subsequent strokes. The thermal effect on a metal object depends on this charge at the point of strike. Its probability of occurrence can be described by a logarithmic normal distribution; therefore, it is plotted as a straight line in this special coordinate system.

According to this diagram, the highest values occur in the case of a positive stroke. The total charge is higher when taking into account the continuous currents, compared to the impulses alone. It is equal to the integral of square current i2. This parameter determines the thermal effect of the lightning current streaming along a conductor.

This energy also characterises the dynamic force that can cause damage in a structure when struck by lightning. Its probability of occurrence can be described with logarithmic normal distribution; therefore, it is plotted by a straight line in this special coordinate system. As shown by the diagram, the highest values occur in the case of a positive stroke.

Distribution functions The distribution function expresses the probability P that a variable is lower than X. This is a special coordinate system equipped with logarithmic scale on the abscissa and Gaussian scale on the ordinate. The coefficient s determines the slope of the line. It depends on the deviation of distribution but it is not identical to it. In contrast, the blue marked formula and diagram give the probability of exceeding X. In practice, the latter version is mostly used. It represents a normal distribution that takes the value 0. The coefficient s depends on the deviation of distribution, as shown earlier.

In a linear scaled diagram, this function is plotted with a curve going from zero to one if the argument X grows from zero to infinity. The program displays several topics when the following items are selected: All phenomena: from Properties of ball lightning to Discharge to the ionosphere.

All over ball lightning: from Properties of ball lightning to Photos of ball lightning. Ball lightning theories: to Theory of magnetic vortex. Properties of ball lightning Ball lightning is the most mysterious phenomenon of atmospheric electricity. There are some general problems: it unexpectedly appears anywhere, it can be seen only from a short distance, its lifetime is short and it has never been artificially reproduced.

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Regarding these properties, no measurements have been possible, and they are known only from the descriptions of eyewitnesses. Because of the sudden appearance of ball lightning, these descriptions are often uncertain. Some experts are sceptical of the actual existence of ball lightning, but with so many observations, it certainly should be accepted as a real phenomenon [8, 23]. Based on the lightning development, two processes could be suggested as the origins of ball lightning. When the channel of the downward leader is interrupted at high altitude, the ionised section left behind is separated and after contraction, the lightning event is presented as a ball.

This process is shown on the left of the screen. Following the main discharge the channel cools unequally and an ionised region is retained. In this way, ball lightning can be created from the main discharge of lightning, as shown on the right. According to some observations, ball lightning has been sighted in absence of any lightning, or just in clear weather.

These cases cannot be explained yet. Nevertheless, red and orange colours occur most frequently, which correspond to lower temperatures than those associated white and yellow. It is interesting that blue and violet colours have been reported with large diameter ball phenomena. If the tree is in leaf, the leaves wilt and the tree will probably die within a few days. If the tree survives long enough to leaf out the following spring, then the chances of recovery are much greater. Watering and fertilization are suggested to reduce tree stress.

Generally, when lightning damage has created hazardous broken branches, corrective pruning should be done. However, waiting two to six months is recommended before doing major and expensive corrective pruning to assess whether the tree will recover. If during this waiting period, the tree shows no obvious signs of decline, then the pruning is probably worth the expense. Consult with a certified arborist for recommendations concerning the health of your damaged tree.

Commonly prescribed practices are water management, bark repair, pruning, fertilization, pest management and tree monitoring. Expensive treatments should not be taken until the tree appears to be making a recovery. Otherwise, when it becomes obvious that the tree will not recover from the lightning strike, the tree should be removed. Historic, rare, and specimen trees, especially when they are the center of landscapes or they shade or frame recreational areas, are valuable and can be protected by a properly installed lightning protection system.

Trees with special significance, or that people or animals might move under in a storm, should be protected. Tree lightning protection is expensive in labor and materials. Lightning protection systems must be installed properly with correct materials to insure long-term protection. For example, aluminum should not be used for any link in a system, nor should solid wire of any type be used.

It is essential to consult with a trained arborist or urban forester, and a lightning protection system installer before designing a protection system for a tree. Lightning protection systems in trees do not attract lightning. The purpose of a protection system is to dilute and slowly release electrical charge potential between the ground and cloud. Trees are not good conductors of electricity but can act as a better conduit than air. Participant from Arnhem continuously to Uppsala. Research fields: Study on probability of lightning stroke and efficiency of lightning protection Problems of electromagnetic compatibility EMC in connection of lightning Evaluation of risk of damage due to lightning stroke Computation of electric and magnetic fields due to high voltage transmission lines Industrial electrostatics Modelling of polarisation processes in dielectrics History of science and technology.

Participation in industrial development projects: Design of mobile high voltage test equipment in auto bus for Hungarian Electricity Trust, Electric Works of Budapest and two electric power distribution firms. Design of two high voltage test laboratories for ceramic industry. Study of electrostatic charging phenomenon at middle wave radio antennas. Guide for lightning protection of television relay stations. Lightning protection of the buildings: the Hungarian Parliament and the cathedral of Budapest, Lightning protection of a nuclear power plant in Hungary, a kV and some kV — kV high voltage overhead stations.