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Lightning Rapid advancing column and return streamers According to Prophet Mohammad Hadith

 

Hussain Yousef Omari

Physics Dept./ Mutah University/ JORDAN

rashed@mutah.edu.jo

A storm: is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather. It may be marked by strong wind, thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting some substance through the atmosphere (as in a dust storm, snowstorm, hailstorm, etc) ([1]).

العواصف الرعدية

A thunderstorm:  ([2])

A thunderstorm, also known as an electrical storm, a lightning storm, or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder.[1] The meteorologically-assigned cloud type associated with the thunderstorm is the cumulonimbus. Thunderstorms are usually accompanied by strong winds, heavy rain and sometimes snow, hail, or no precipitation at all. Those which cause hail to fall are known as hailstorms. Thunderstorms may line up in a series or rainband, known as a squall line. Strong or severe thunderstorms may rotate, known as supercells. While most thunderstorms move with the mean wind flow through the layer of the troposphere in which they occupy, vertical wind shear causes a deviation in their course at a right angle to the wind shear direction.

Thunderstorms can generally form and develop in any geographic location, perhaps most frequently within areas located at mid-latitude when warm moist air front collides and border cool air fronts.[2] Thunderstorms are responsible for the development and formation of many severe weather phenomena. Thunderstorms, and the phenomena that occurs along with it, can produce numerous risks and hazards to populations and landscapes. Damages that result from thunderstorms are mainly inflicted by downburst winds, large hailstones, and flash flooding caused by heavy precipitation. Stronger thunderstorm cells are capable of producing tornadoes and waterspouts.

There are four types of thunderstorms: single cell, multicell cluster, multicell lines, and supercells. Supercell thunderstorms are the strongest and the most associated with severe weather phenomena. Mesoscale convective systems formed by favorable vertical wind shear within the tropics and subtropics are responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires with the heat generated from the cloud-to-ground lightning that accompanies them. A variety of methods are used to study thunderstorms, such as weather radar, weather stations, and video photography. Past civilizations held various myths concerning thunderstorms and their development as late as the Eighteenth Century. Other than within the Earth's atmosphere, thunderstorms have also been observed on Jupiter and Venus.

Lightning

Stepped leader:  قائد (مخطّط) مسار التفريغ

Meaning of Stepped:

Stepped (step), adj. having a step or steps; formed in a series of steps: a stepped pyramid. (Barnhart, Clarence L. and Barnhart, Robert K.  The World Book Dictionary, FE Chicago, 1977, two volumes.; Vol. 2; p. 2052)

Stepped 2

Definition: Provided with a step or steps; having a series of offsets (steadiness) or parts resembling the steps of stairs; as, a stepped key. ([3])

Stepped leader ([4]).

A stepped leader (possibly also referred to as a step leader) is a path of ionized air which extends downward from a thundercloud during the initial stages of atmospheric breakdown during a lightning strike. Often, there are multiple, branching stepped leaders. As the step leaders form, these branches of ionized air form in a stepwise fashion, followed by a short period of inactivity, until the final step leader reaches the ground, a tall object on the ground, or a positive streamer extending upward from a ground object. At this point, the lightning strike begins as an extremely large negative electric current that flows along the path defined by the stepped leaders from the thundercloud into to the ground. This flow of current is often referred to as the return stroke.

Stepped leaders appear to only move in quantized steps of approximately 50-100 feet at a time with a 20 to 50 microsecond pause between steps, and may either branch or proceed directly to ground.

Stepped leader—The initial leader of a lightning discharge; an intermittently (from time to time) advancing column of high ionization and charge that establishes the channel for a first return stroke.

The abnormal characteristic of this type of leader is its stepwise growth at intervals of about 50– 100 μs. The velocity of growth during the brief intervals of advance, each only about 1 μs in duration, is quite high (about 5 × 107 m s−1), but the long stationary phases reduce its effective speed to only about 5 × 105 m s−1. To help explain its mode of advance, the concept of a pilot streamer was originally suggested, but has been supplanted by analogy to recent work on long laboratory sparks ([5]).

The initial streamer of a lightning discharge; an intermittently advancing column of high ion density which established the channel for subsequent return streamers and dart leaders. ([6])

A stepped leader (possibly also referred to as a step leader) is a path of ionized air which extends downward from a thundercloud during the initial stages of atmospheric breakdown during a lightning strike. Often, there are multiple, branching stepped leaders. As the step leaders form, these branches of ionized air form in a stepwise fashion, followed by a short period of inactivity, until the final step leader reaches the ground, a tall object on the ground, or a positive streamer extending upward from a ground object. At this point, the lightning strike begins as an immensely large negative electric current along the path defined by the stepped leaders, but in the opposite direction: from ground to cloud. This current is often referred to as the return stroke.

Stepped leaders appear to only move in quantized steps of approximately 50–100 feet at a time with a 20 to 50 microsecond pause between steps, and may either branch or proceed directly to ground. ([7])

Characteristics of an `average` lightning flash:-

Stepped leader takes 0.005 secs to develop.

A shock wave of gaseous plasma rushes along this path or channel created by the stepped leader and large currents flow to produce temperatures in excess of 30,000 degrees C. This large current discharge is called the return stroke.

Return stroke takes 0.0001secs (about 1/3 the speed of light).

Return stroke

200,000,000 volts potential over length.  Current 50,000 Amps.  Core temperature 25,000 C (about 5x hotter than surface of the Sun).  Length 5 miles.  There are 1200 thunderstorms per hour over the Earth`s surface. Each will have about 1,000 flashes of lightning. A thunder cell within a cumulo-nimbus cloud recharges in 30 seconds.

Lightning

From Wikipedia, the free encyclopedia

275px-Blesk

Lightning striking a tower in Banská Bystrica, Slovakia.

Lightning is an atmospheric discharge of electricity accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms.[1] In the atmospheric electrical discharge, a leader of a bolt of lightning can travel at speeds of 60,000 m/s (130,000 mph), and can reach temperatures approaching 30,000°C (54,000°F), hot enough to fuse silica sand into glass channels known as fulgurites which are normally hollow and can extend some distance into the ground.[2][3] There are some 16 million lightning storms in the world every year.[4]

Lightning can also occur within the ash clouds from volcanic eruptions, or can be caused by violent forest fires which generate sufficient dust to create a static charge.[1][5]

How lightning initially forms is still a matter of debate:[6]

 Scientists have studied root causes ranging from atmospheric perturbations (wind, humidity, friction, and atmospheric pressure) to the impact of solar wind and accumulation of charged solar particles.[4] Ice inside a cloud is thought to be a key element in lightning development, and may cause a forcible separation of positive and negative charges within the cloud, thus assisting in the formation of lightning.[4]

Lightning comes from thunderclouds, known as cumulonimbus, which are created when hot moist air rises into the atmosphere and condenses. Hot air rises when heated by the sun, carrying water vapor into the sky. As it rises, the hot air mingles with colder air, and the moisture condenses into water droplets. Clouds are created when these water droplets become visible. The droplets increase in size as the cloud grows and eventually become so heavy that they fall as rain. Thunderclouds are large, anvil-shaped masses that can stretch miles across at the base, and reach 40,000 feet or more into the atmosphere.

Norman, OK lightning strike.

 

The genesis of lightning is a subject of great theoretical debate, says Dr. Vladimir Rakov of the Lightning Research Center at the University of Florida. We know that electrical charges build up within thunderclouds, but there is no single theory that fully describes why:

(...قالوا أخبرنا ما هذا الرعد قال ملك من ملائكة الله عز وجل موكل بالسحاب بيده أو في يده مخراق من نار يزجر به السحاب يسوقه حيث أمره الله عز وجل قالوا فما هذا الصوت الذي نسمع قال صوته قالوا صدقت ...)

One commonly discussed thesis suggests that small cloud particles acquire a positive charge, while other larger particles become negatively charged. These particles eventually separate, and the upper part of the cloud becomes positively charged, while the lower part becomes negatively charged.

The attraction, or electrical potential, between the positive and negative charges eventually grows strong enough to overcome the air's resistance to electrical flow. Racing toward each other, the charges connect, completing an electrical circuit, and discharging the accumulated electricity as lightning. Cloud-to-cloud lightning is the most common form of electrical discharge. Only about one-third of all discharges are cloud-to-ground. Bolts that shoot from cloud-to-air, known as "bolts from the blue," are even less common, but can strike up to 10 miles away.

When the current is discharged, it is accompanied by a flash containing millions of volts of electricity. This is a huge amount of energy, and the surrounding air is heated up to 54,000° F, five times hotter than the surface temperature of the Sun. The rapidly expanding heated air also produces tremendous shock waves, which become audible as the sound of thunder ([8]) By Micah Fink.

Thunder: 

The sound that follows a flash of lightning and is caused by sudden expansion of the air in the path of the electrical discharge.

Thunder is the sound that lightning makes. Sounds simple but why does lightning make a sound. Any sound you hear is made up of vibrations, the vibrations travel through the air as waves until they reach your ear.

This means lightning must cause some vibrations.

Lightning is a huge discharge of electricity. When lightning strikes huge amounts of electricity shoots through the air, this causes two things to happen.

1. The electricity hits the air and starts it vibrating, anything vibrating causes a sound.

2.The lightning is also very hot and heats up the air around it. Hot air gets bigger: it expands. As lightning is very hot the air gets bigger very quickly and pushes against the air particles starting another vibration.

These vibrations are what you are hearing when you hear thunder, the rumbling of thunder is caused by the vibration or sound bouncing of the ground and the clouds.

البرق في الأحاديث النبوية الشريفة

- أقبلت اليهود إلى رسول الله صلى الله عليه وسلم فقالوا يا أبا القاسم إنا نسألك عن خمسة أشياء فإن أنبأتنا بهن عرفنا أنك نبي واتبعناك فأخذ عليهم ما أخذ إسرائيل على بنيه إذ قالوا { الله على ما نقول وكيل } قال هاتوا قالوا خبرنا كيف تؤنث المرأة وكيف تذكر قال يلتقي الماءان فإذا علا ماء الرجل ماء المرأة أذكرت وإذا علا ماء المرأة ماء الرجل أنثت قالوا أخبرنا ما حرم إسرائيل على نفسه قال كان يشتكي عرق النسا فلم يجد شيئا يلائمه إلا ألبان كذا وكذا قال بعضهم يعني الإبل فحرم لحومها قالوا صدقت قالوا أخبرنا ما هذا الرعد قال ملك من ملائكة الله عز وجل موكل بالسحاب بيده أو في يده مخراق من نار يزجر به السحاب يسوقه حيث أمره الله عز وجل قالوا فما هذا الصوت الذي نسمع قال صوته قالوا صدقت إنما بقيت واحدة إنما نبايعك إن أخبرتنا إنه ليس من نبي إلا له من يأتيه بالخبر فأخبرنا عن صاحبك قال جبريل عليه السلام قالوا جبريل ذلك الذي ينزل بالعذاب والحرب والقتال وهو عدونا لو قلت ميكائيل الذي ينزل بالرحمة والنبات والقطر لكان فأنزل الله عز وجل { قل من كان عدوا لجبريل } الآية وفي رواية كلما أخبرهم بشيء فصدقوه قال اللهم اشهد وقال فيها أنشدكم بالله الذي أنزل التوراة على موسى هل تعلمون أن هذا النبي الأمي تنام عيناه ولا ينام قلبه قالوا اللهم نعم وقال أيضا فإن وليي جبريل ولم يبعث الله نبيا قط إلا وهو وليه ) (الراوي: عبدالله بن عباس المحدث: الهيثمي - المصدر: مجمع الزوائد - الصفحة أو الرقم: 8/244، خلاصة حكم المحدث: رجالهما ثقات)

- أقبلت يهود إلى رسول الله صلى الله عليه وسلم فقالوا : يا أبا القاسم إنا نسألك عن خمسة أشياء فإن أنبأتنا بهن عرفنا أنك نبي واتبعناك فأخذ عليهم ما أخذ إسرائيل على بنيه إذ قالوا : الله على ما نقول وكيل قال : هاتوا قالوا : أخبرنا عن علامة النبي قال : تنام عيناه ولا ينام قلبه قالوا : أخبرنا كيف تؤنث المرأة وكيف تذكر قال : يلتقي الماءان فإذا علا ماء الرجل ماء المرأة أذكرت وإذا علا ماء المرأة ماء الرجل أنثت قالوا : أخبرنا ما حرم إسرائيل على نفسه قال : كان يشتكي عرق النسا فلم يجد شيئا يلائمه إلا ألبان كذا وكذا قال أبي : قال بعضهم : يعني الإبل فحرم لحومها قالوا : صدقت قالوا : أخبرنا ما هذا الرعد قال : ملك من ملائكة الله عز وجل موكل بالسحاب بيده أو في يده مخراق من نار يزجر به السحاب يسوقه حيث أمر الله قالوا : فما هذا الصوت الذي يسمع قال : صوته قالوا : صدقت إنما بقيت واحدة وهي التي نبايعك إن أخبرتنا بها فإنه ليس من نبي إلا له ملك يأتيه بالخبر فأخبرنا من صاحبك قال : جبريل عليه السلام قالوا : جبريل ذاك الذي ينزل بالحرب والقتال والعذاب عدونا لو قلت ميكائيل الذي ينزل بالرحمة والنبات والقطر لكان فأنزل الله عز وجل : { من كان عدوا لجبريل } إلى آخر الآية ) (الراوي: عبدالله بن عباس المحدث: أحمد شاكر - المصدر: مسند أحمد - الصفحة أو الرقم، 4/161، خلاصة حكم المحدث، إسناده صحيح)

- أقبلت يهود إلى النبي صلى الله عليه وسلم فقالوا يا أبا القاسم نسألك عن أشياء إن أجبتنا فيها اتبعناك وصدقناك وآمنا بك قال فأخذ عليهم ما أخذ إسرائيل على نفسه قالوا الله على ما نقول وكيل قالوا أخبرنا عن علامة النبي قال تنام عيناه ولا ينام قلبه قالوا فأخبرنا كيف تؤنث المرأة وكيف تذكر قال يلتقي الماءان فإن علا ماء المرأة ماء الرجل أنثت وإن علا ماء الرجل ماء المرأة أذكرت قالوا صدقت فأخبرنا عن الرعد ما هو قال الرعد ملك من الملائكة موكل بالسحاب بيديه أو في يده مخراق من نار يزجر به السحاب والصوت الذي يسمع منه زجره السحاب إذا زجره حتى ينتهي إلى حيث أمره ) (الراوي: عبدالله بن عباس المحدث: الألباني - المصدر: السلسلة الصحيحة - الصفحة أو الرقم: 4/191، خلاصة حكم المحدث: صحيح)

والصوت الذي يسمع منه زجره السحاب إذا زجره حتى ينتهي إلى حيث أمره .

- أقبلت يهود إلى رسول الله صلى الله عليه وعلى آله وسلم فقالوا : يا أبا القاسم إنا نسألك عن خمسة أشياء فإن أنبأتنا بهن عرفنا أنك نبي واتبعناك فأخذ عليهم ما أخذ إسرائيل على بنيه إذ قالوا الله على ما نقول وكيل ، قال : هاتوا . قالوا : أخبرنا عن علامة النبي ، قال : تنام عيناه ولا ينام قلبه, قالوا : أخبرنا كيف تؤنث المرأة وكيف تذكر ؟ قال : يلتقى الماءان فإذا علا ماء الرجل ماء المرأة أذكرت ، وإذا علا ماء المرأة ماء الرجل أنثت ، قالوا : أخبرنا ما حرم إسرائيل على نفسه ؟ قال : كان يشتكي عرق النسا فلم يجد شيئا يلائمه إلا ألبان كذا وكذا ، قال عبد الله ، قال أبي ، . قال بعضهم: يعني الإبل فحرم لحومها، قالوا: صدقت، قالوا: أخبرنا ما هذا الرعد ؟ قال: ملك من ملائكة الله عز وجل موكل بالسحاب بيده أو في يده مخراق من نار يزجر به السحاب يسوقه حيث أمر الله ، قالوا : فما هذا الصوت الذي يسمع ؟ قال : صوته ، قالوا : صدقت ، إنما بقيت واحدة وهي التي نبايعك إن أخبرتنا بها فإنه ليس من نبي إلا له ملك يأتيه بالخبر فأخبرنا من صاحبك ؟ قال : جبريل عليه السلام ، قالوا : جبريل ذاك الذي ينزل بالحرب والقتال والعذاب عدونا لو قلت ميكائيل الذي ينزل بالرحمة والنبات والقطر لكان . فأنزل الله عز وجل : { من كان عدوا لجبريل } إلى آخر الآية . ) (الراوي: عبدالله بن عباس المحدث: الوادعي - المصدر: صحيح أسباب النزول - الصفحة أو الرقم: 22، خلاصة حكم المحدث: [فيه] بكير بن شهاب قد خولف لكن له طرق)

- (الرعد ملك من ملائكة الله ، موكل بالسحاب ، معه مخاريق من نار ، يسوق بها السحاب حيث شاء الله ) (الراوي: عبدالله بن عباس المحدث: الألباني - المصدر: صحيح الجامع - الصفحة أو الرقم: 3553، خلاصة حكم المحدث: حسن).

( معه مخاريق ) ‏:  جمع مخراق.  وهو في الأصل ثوب يلف ويضرب به الصبيان بعضهم بعضا, وأراد به هنا آلة تزجر بها الملائكة السحاب ‏.  ‏" يسوق "‏: ‏أي الملك الموكل بالسحاب. ‏" بها " ‏: ‏أي بتلك المخاريق‏.  ‏( زجرة ) ‏:‏ أي هو زجرة‏.  ‏(إذا زجره) ‏: ‏أي إذا ساقه.  قال الله تعالى: { فالزاجرات زجرا } يعني الملائكة تزجر السحاب؛ أي تسوقه‏.  ‏" حتى ينتهي"‏: ‏أي يصل السحاب ‏( إلى حيث أمر ) (تحفة الأحوذي بشرح جامع الترمذي).

مِفعال بكسر الميم اسـم آلـة ([9]):

مثل : منشار ، مسمار ، محراث ، ملقاط ، مثقاب ، مفتاح ، مزمار .

ومنه قوله تعالى : { إن الله لا يظلم مثقال ذرة } 40 النساء .

وقوله تعالى : { ولا تنقصوا المكيال والميزان } 84 هود .

وقوله تعالى : { وعنده مفاتح الغيب } 59 الأنعام .

مِخْراق اسم الآلة من الفعل خرق على وزن مِفْعال

والمخاريق واحدها مخراق ([10]).

هذه المخاريق يستخدمها ملائكة السّحاب من أجل إحداث فروق جهد هائلة ممّا يتسبّب بحدوث البرق (الشحنات تخرق مسارها بين السحب التي تتوسّط هذه المخاريق بسبب فرق الجهد الذي تحدثه الآلات المسماة المخاريق) .  والرّعد هو الصوت الذي يحصل نتيجة التفريغ الكهربائي بين السّحب .  يبدو من الحديث أنّ فروق الجهد الهائلة والمسببة للتفريغ هي بفعل المخاريق التي تستخدمها ملائكة السّحاب.

الحديث : (قالوا أخبرنا ما هذا الرعد قال ملك من ملائكة الله عز وجل موكل بالسحاب بيده أو في يده مخراق من نار يزجر به السحاب يسوقه حيث أمره الله عز وجل قالوا فما هذا الصوت الذي نسمع قال صوته قالوا صدقت).  ليس معنى الحديث أنّ الرّعد هو ملك.  المعنى إليك تفسير الرّعد: (ملك من ملائكة الله عز وجل موكل بالسحاب بيده أو في يده مخراق من نار يزجر به السحاب يسوقه حيث أمره الله عز وجل قالوا فما هذا الصوت الذي نسمع قال صوته قالوا صدقت).  (قال صوته) : الهاء عائدة على عمليّة الزّجر؛ أي الصوت ناجم عن عمليّة الزّجر التي أحدثها التفريغ الكهربائي.  الرّعد (الصوت الذي يلي عمليّة التفريغ) وينتج عن عمليّة زجر السّحاب بآلة المخاريق (جمع مخراق) والمتسبّبة في إحداث فرق الجهد الهائل الذي يحدث البرق ؛ فنسمع الرّعد.  وبالمناسبة لا يوجد أيّ تفسير علمي ثابت يبيّن كيفيّة تنامي فرق الجهد الهائل.

ألم تروا إلى البرق كيف يمر ويرجع في طرفة عين ؟

(Hast thou not seen how does the lightning come and return in the blink of an eye?)

- (يجمع الله تبارك وتعالى الناس. فيقوم المؤمنون حتى تزلف لهم الجنة . فيأتون آدم فيقولون : يا أبانا استفتح لنا الجنة . فيقول : وهل أخرجكم من الجنة إلا خطيئة أبيكم آدم ! لست بصاحب ذلك . اذهبوا إلى ابني إبراهيم خليل الله . قال فيقول إبراهيم : لست بصاحب ذلك . إنما كنت خليلا من وراء وراء. اعمدوا إلى موسى صلى الله عليه وسلم الذي كلمه الله تكليما. فيأتون موسى صلى الله عليه وسلم فيقول: لست بصاحب ذلك. اذهبوا إلى عيسى كلمة الله وروحه . فيقول عيسى صلى الله عليه وسلم : لست بصاحب ذلك . فيأتون محمدا صلى الله عليه وسلم. فيقوم فيؤذن له . وترسل الأمانة والرحم . فتقومان جنبتي الصراط يمينا وشمالا . فيمر أولكم كالبرق ، قال قلت : بأبي أنت وأمي ! أي شيء كمر البرق ؟ قال : ألم تروا إلى البرق كيف يمر ويرجع في طرفة عين ؟ ثم كمر الريح . ثم كمر الطير وشد الرجال . تجري بهم أعمالهم . ونبيكم قائم على الصراط يقول : رب ! سلم سلم . حتى تعجز أعمال العباد . حتى يجيء الرجل فلا يستطيع السير إلا زحفا . قال وفي حافتي الصراط كلاليب معلقة . مأمورة بأخذ من أمرت به . فمخدوش ناج ومكدوس في النار . والذي نفس أبي هريرة بيده ! إن قعر جهنم لسبعون خريفا . ) (الراوي: أبو هريرة و حذيفة بن اليمان المحدث: مسلم - المصدر: صحيح مسلم - الصفحة أو الرقم: 195، خلاصة حكم المحدث: صحيح).

- (يجمع الله الناس فيقول المؤمنون، حين تزلف الجنة، فيأتون آدم، فيقولون يا أبانا استفتح لنا الجنة، فيقول: وهل أخرجكم من الجنة إلا خطيئة أبيكم آدم ؟ لست بصاحب ذلك ، إنما كنت خليلا من وراء وراء . اعمدوا إلى ابني موسى ، الذي كلمه الله تكليما ، فيأتون موسى ، فيقول لست بصاحب ذلك ، اذهبوا إلى كلمة الله وروحه عيسى ، قال : فيقول عيسى ، لست بصاحب ذلك ، فيأتون محمدا – صلى الله عليه وسلم – فيقوم فيؤذن له ، وترسل معه الأمانة والرحم ، فيقفان على الصراط ، يمينه وشماله ، فيمر أولكم ، كمر البرق ، قلت : بأبي أنت وأمي : أي شيء مر البرق قال : ألم تر إلى البرق كيف يمر ، ثم يرجع في طرفة عين ، كمر الريح ، ومر الطيور ، وشد الرجال ، تجري بهم أعمالهم ، ونبيكم – صلى الله عليه وسلم – قائم على الصراط ، يقول رب سلم ، سلم ، قال : حتى تعجز أعمال الناس ، حتى يجيء الرجل ، فلا يستطيع أن يمر إلا زحفا ، قال : وفي حافتي الصراط كلاليب معلقة مأمورة تأخذ من أمرت به ، فمخدوش ناج ، ومكدوس في النار . والذي نفس أبي هريرة بيده : إن قعر جهنم لسبعين خريفا

الراوي: أبو هريرة و حذيفة بن اليمان المحدث: ابن خزيمة - المصدر: التوحيد - الصفحة أو الرقم: 600/2، خلاصة حكم المحدث: أشار في المقدمة أنه صح وثبت بالإسناد الثابت الصحيح).

The rest of the article is to discuss the following question raise by Prophet's Hadith:

ألم تروا إلى البرق كيف يمر ويرجع في طرفة عين ؟

(Hast thou not seen how does the lightning come and return in the blink of an eye?)

هنالك كيفيّة لمرور البرق:

Lightning has a step or steps; it is formed in a series of steps.  It is Provided with a step or steps; having a series of offsets (steadiness) or parts resembling the steps of stairs ([11]).

Stepped leader ([12])

A stepped leader (possibly also referred to as a step leader) is a path of ionized air which extends downward from a thundercloud during the initial stages of atmospheric breakdown during a lightning strike. Often, there are multiple, branching stepped leaders. As the step leaders form, these branches of ionized air form in a stepwise fashion, followed by a short period of inactivity, until the final step leader reaches the ground, a tall object on the ground, or a positive streamer extending upward from a ground object. At this point, the lightning strike begins as an extremely large negative electric current that flows along the path defined by the stepped leaders from the thundercloud into to the ground. This flow of current is often referred to as the return stroke.

هنالك مرور و رجوع في طرفة عين:

Lightning streaks inside a cloud, between clouds, and from clouds to the ground. Lightning is a flow of electrons (a negative charge) that zigzags downward in a forked shaped pattern (scientists call this a step leader).

Stepped leaders appear to only move in quantized steps of approximately 50-100 feet at a time with a 20 to 50 microsecond pause between steps, and may either branch or proceed directly to ground.

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A lightning flash resolved by Boys camera at 26,000 frames per second

A lightning flash starts downwards as a thin moving leader with a very luminous tip. The second tip advances in this the stepped leader by some 20 to 50 meters advance on the first step. The steps, sometimes branching, stab downwards until near to the ground.  As it nears the earth, a stream of positive charges moves up to the charge of electrons (negative charge). When they meet, the power flows. We can't see this because it moves too fast (first stroke). The return flow (positive charge) moves upward more slowly. This is what we see and call lightning (return stroke). If there is a flicker, the upward stroke is repeating the process.

The return stroke (electrical positive charge that travels from the ground to a thundercloud) releases tremendous energy, bright light and thunder. 

Lightning

lightning_med

 

 

Lightning is, generally, any and all forms of visible electrical discharge produced by thundershowers. There are many names. Directly from the Glossary of Meteorology, different forms include: streak lightning, forked, sheet, heat lightning, and ball lightning.

 

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Lightning!
by Mark McEuen

 

 

 

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هنالك كيفيّة:

Throughout history, man has been fascinated by lightning. Ancient peoples thought it was the work of the gods. In medieval Europe, church bells were rung during thunderstorms in the belief that it would prevent lightning from striking the spire (a practice which resulted in the deaths of literally hundreds of bell ringers). In more recent times, Ben Franklin proved that lightning is merely electricity with his famous kite experiment and invented the lightning rod in order to protect buildings from its effects (Mark McEuen).

A Lightning Bolt

The structure of a typical lightning bolt is surprisingly complex. It begins with a large thunderstorm. Through a process that is not yet fully understood, charge separates within the cloud, causing the top to become positively charged and the bottom negatively charged. This negative charge attracts a "shadow" of positive charge on the ground below. When enough charge accumulates, a lightning bolt occurs (Mark McEuen). ([13])

flash

A lightning bolt happens in a series of stages. First, a faint step leader emerges from the base of the cloud. It moves toward the ground in steps of 50 meters or so, pausing very briefly between steps. Often it branches as it goes down, which is why so many lightning bolts "fork". When the step leader nears the ground, it attracts "streamers" of positive charge from the ground. When it finally connects with one of these streamers, a brilliant return stroke occurs as the charge drains out of the ionized channel left by the step leader. The charge nearest the ground goes first, causing the return stroke to propagate upward. Often this is followed by another relatively faint cloud-to-ground dart leader, which is rapidly followed by another return stroke. This process can take place up to 40 times, which is why many lightning bolts are seen to flicker (Mark McEuen).

Multiple-stroke flashes of lightning ([14])

Abstract

Slow-speed rotating all-sky cameras were used to photograph flashes of lightning in the vicinity of Pretoria and Johannesburg, South Africa. The frequency distribution of the number of strokes per flash was determined for 1001 flashes which occurred on a total of 35 days during five summers. This distribution agrees with other results obtained recently in the same region of South Africa using other methods, but a higher proportion (57%) of single-stroke flashes was found compared with previous results (13%). Individual storms differed widely: some produced only single-stroke flashes but many multiple-stroke flashes were observed in others. Flashes with simultaneous multiple grounds were uncommon but one storm produced a relatively high proportion of such flashes ([15]).

 

Observation of multiple stroke and multipoint discharges by means of UHF interference ([16])

 

 

Abstract

Results of interferometric observations of cloud-to-ground flashes in Darwin (Australia) have been analyzed to investigate some features of the lightning phenomenon. Our study focused on comparison between multipoint and multiple negative cloud-to-ground flashes. The speed of leaders was estimated with submillisecond resolution for both multipoint and multiple strokes. Leaders preceding the first stroke in multiple-stroke flashes progress in a stepped fashion, and their behavior exhibits the same features as leaders in multipoint flashes. The estimated average speed of the leaders is on the order of 105 m/s, and the mean step length is found to be 96 m with a mean pause time of 73 mgrs. The running time of the leader found from results of these observations has a mean value of 89 mgrs. The duration of UHF radiation bursts generated by leaders propagating along previously formed channels ranges from 0.2 to 55.3 ms with a mean value of 7.5 ms. By contrast, the duration of UHF radiation in leaders preceding multipoint strokes ranges from 21.1 to 90.6 ms with a mean value of 47.5 ms. The time intervals between strokes that strike at the same point as the previous stroke range from 22.5 to 330.6 ms with a mean value of 75.1 ms, while intervals between strokes in multipoint flashes range from 55.6 to 633.7 ms with a mean value of 149.1 ms. All leaders preceding multipoint strokes start in the same region inside the cloud. © 2001 Scripta Technica, Electr Eng Jpn, 134(4): 62-69, 2001. ([17])

Review of lightning properties from electric field and TV observations.  Vladimir A. Rakov/ Department of Electrical Engineering, University of Florida, and Gainesville Martin A. Uman, Department of Electrical Engineering, University of Florida, and Gainesville Rajeev Thottappillil/ Department of Electrical Engineering, University of Florida, Gainesville

From analysis of simultaneous electric field and TV records of 76 negative cloud-to-ground lightning flashes in Florida, various lightning properties have been determined and several new facets of lightning behavior inferred. Only 17 % of the flashes were single-stroke flashes, less than half the commonly claimed percentage (e.g., Anderson and Eriksson, 1980). The initial electric field peak (and, by inference, current peak) for the only strokes in single-stroke flashes was smaller than for first strokes in multiple-stroke flashes. Half of all flashes, single and multiple stroke, struck ground at more than one point, with the spatial separation between the channel terminations being up to many kilometers. One third of multiple-stroke flashes had at least one subsequent stroke whose distance-normalized initial electric field peak exceeded that of the first stroke in the flash. Thus such flashes are not unusual, contrary to the implication of most lightning protection and lightning test standards. Subsequent strokes of the order of 2 through 4 were more likely to create a new channel termination on ground than strokes of the order of 5 and higher. Further, leaders of lower-order subsequent strokes following previously formed and not-too-aged (100 ms or less) channels were more likely to show stepping, as opposed to continuous propagation (i.e., to be dart-stepped leaders rather than dart leaders), than were leaders of higher-order strokes. Finally, lower-order subsequent return strokes exhibited a larger initial electric field peak than did higher-order strokes. The second leader of the flash (the first subsequent leader) encounters the least favorable propagation conditions of all subsequent strokes: more than half of the second leaders either deflected from the previously formed path to ground or propagated in a stepped, as opposed to a continuous, fashion along the lowest part of that path. It is important to note that inter stroke intervals preceding second strokes are similar to or shorter than those preceding higher-order strokes. These observations indicate that channel conditions for the propagation of a subsequent leader are determined not just by the immediately preceding channel heating and cooling processes but rather by the entire channel history. In particular, the status of the channel apparently depends on the number of strokes that have participated in its cumulative conditioning. The overwhelming majority of long continuing currents, those with a duration longer than 40 ms, were initiated by subsequent strokes of multiple-stroke flashes as opposed to either the first stroke in a multiple-stroke flash or the only stroke in a single-stroke flash. Strokes that initiate such long continuing currents were (1) relatively small (in terms of both return-stroke field peak and, as determined from an independent study in New Mexico, stroke charge), (2) followed relatively short inter stroke intervals, and (3) showed a tendency to be preceded by a relatively large stroke. Millisecond-scale K and M electric field changes appeared different in terms of both microsecond-scale pulse content and inter event time intervals. Often no microsecond-scale K and M field pulses were detected. When they were present, such pulses were highly variable and sometimes irregular in wave shape, as opposed to the alleged characteristic K-pulse waveform described by Arnold and Pierce (1964), which has been extensively used in atmospheric radio-noise studies. There is a remarkable similarity between many lightning characteristics in Florida and in New Mexico.

Citation: Rakov, V. A., M. A. Uman, and R. Thottappillil (1994), Review of lightning properties from electric field and TV observations, J. Geophys. Res., 99(D5), 10,745–10,750.

(http://www.agu.org/pubs/crossref/1994/93JD01205.shtml)

Subsequent return strokes:

Ref.

Leaders: A channel of charged air created by excess electrons in a thunderstorm cloud. A leader reaches from the cloud to the ground below, looking for positive charges. 

Protons:  A sub-atomic (really, really small) particle that carries a positive energy charge.

Streamers: A channel of charged air created by protons on the ground. They are created when leaders are created, and reach from the ground to the sky looking for a leader to connect with.

Thunder:  The sound that follows a flash of lightning and is caused by sudden expansion of the air in the path of the electrical discharge.

1-journal-of-lightning-research-volume_1_2007[1].pdf

 

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The Cumulo-Nimbus Cloud

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The Cumulo-Nimbus Cloud

http://books.google.jo/books?id=U6lCL0CIolYC&lpg=PA1&ots=93Gvp2OxwR&dq=lightning%20%20return%20stroke&pg=PA4#v=onepage&q=lightning%20%20return%20stroke&f=false

Children used to call them Cabbage Clouds as the Cumulus billowed upwards on a Summer day. When convection carries one high enough its top its drawn outwards by the winds of the Stratosphere. It has the appearance of the beak of a blacksmith`s anvil.

Such a cloud is 50,000 feet or so high and its temperature at the top is - 50 degrees C. Its water mass is about 300,000 tons in the form of particles ranging in size from the Aitken nuclei a few microns in diameter to larger, visible, droplets a fraction of a millimeter in size.

If the air is free from nuclei, dust, pollen grains, meteoritic detritus, the water will be liquid and supercool.

The winds inside the cloud reach speeds of hundreds of miles per hour and circulate the water droplets and ice inside cells/regions within the cloud.

Regions of electrical charge build up within these cells - sometimes called thunder cells. Some may have net positive charge and some net negative charge. It is too simplistic to say that there is one polarity at the top of the cloud and its opposite at the base.

Forms of Lightning

I am referring here only to channel discharges of lightning. We usually see the return stroke oscillating between cloud and ground and cloud to cloud discharges. Inside the cloud may be intra-cloud lightning which lights up the cloud like an enormous glow discharge tube. Discharges may leave the top of the cloud and out into the ionized regions of the ionosphere.

A fighter pilot who bailed out inside a cumulo-nimbus went upwards! For three quarters of an hour he was lifted and dropped by the immense internal winds and described intra cloud lightning as `pillars of blue fire`.

Fork lightning is the name given to the common return discharge cloud to ground.

Sheet lightning is the lighting up of sky and clouds by unseen fork lightning.

Ball lightning denied existence for a long time. A.D. Moore told me of some he had seen. Shortly afterwards my wife was standing at a bus stop when lightning hit the road about twenty yards away and a blue ball nonchalantly bounced down the

Bead lightning appears after a particularly powerful fork lightning. It looks like the lightning discharge channel has broken up into a string of beads - of plasma.

Ribbon Lightning. Powerful horizontal winds blow the fork lightning channel sideways. The appearance of the lightning is like a long flat ribbon reaching from cloud to ground.

From the origin to the discharge of a flash of lightning.

Sources of charge charging processes

Charging Process in Cumulo-Nimbus Decades of investigation have discovered that:-

Ice impacting on ice produces electricity. Water freezing produces electricity. Water freezing - remelting - refreezing produces electricity. Water drops breaking up produce electricity. Droplets drawn out in electric fields redistribute electricity in themselves and add to total charge. Ingestion into the cloud of saline jet droplets from the seas and oceans contribute electricity.

In the Cumulo-Nimbus Cloud the winds, water and temperature generate electric charge.

The major question is not whether these produce electricity, they have been investigated at laboratory level and are known to be true, but does the charging process produce (i) sufficient charge (ii) If so does it do so quickly enough such that when a thunder cell discharges in lightning it can recharge - as is observed - within about thirty seconds?

Workman and others investigated warm clouds which also produced thunderstorms -which brings the ice factor into question.( They also found Cumulo-Nimbus 15miles high.)

Vonnegut did not accept these processes as being the main contributory source of electricity and regarded them as interesting secondary sources. He felt the cloud when it reached a certain height was an electrical conductor on which charge was induced from the ionized upper atmosphere and Earth`s field.

One thing is certain somehow within the whirling of winds, ice and water charge accumulation takes place and builds up in `cells` with net pockets of charge, within the Cumulo-nimbus cloud.

An `Average`Lightning Flash Stephen Gray thought the sounds and sparks in his electrostatic experiments may well be going on in larger scale in thunderstorms.

The invention of the Leyden Jar concentrated minds in the same direction. The discovery that the Leyden Jar spark was oscillatory and not just a simple discharge led to the thought that lightning too may oscillate between cloud and ground - assuming of course that lightning was electrical.

Benjamin Franklin with his kite experiments, the experiment at Marly and others proved that lightning was indeed a gigantic electrical discharge.

But at what voltage? C.T.R. Wilson (Inventor of the Cloud Chamber to examine ions in the air on Ben Nevis) made the obvious common sense deduction, namely:

If a potential difference between electrodes of 10,000 volts produces a spark 1 cm long then a lightning discharge 2km long will have a potential difference between cloud and ground of:-

2 x 1000(meters) x 100 (cms) x 10,000 (volts) = 2,000,000,000volts.

THE BOYS LIGHTNING CAMERA.

C.V. Boys was a great experimental scientist.

Boys decided to move the lenses in front of a fixed film. The lenses in the Boys Camera rotated to give the effect of moving the film at 26,000 frames per second.

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A lightning flash resolved by Boys camera at 26,000 frames per second

A lightning flash starts downwards as a thin moving leader with a very luminous tip. The second tip advances in this the stepped leader by some 20 to 50 metres advance on the first step. The steps, sometimes branching, stab downwards until near to the ground.

Leader charge is negative and of about 5 coulombs over its entire length. Its downward velocity is 150,000 metres per second. The current in the tip is 100Amps.

On nearing the ground the intense electric field of the advancing stepped leader induces an image charge of opposite polarity in the ground and a streamer is initiated upwards. When the two meet a conducting path is established between cloud and ground.

A shock wave of gaseous plasma rushes along this path or channel created by the stepped leader and large currents flow to produce temperatures in excess of 30,000 degrees C. This large current discharge is called the return stroke.

Photographic measurements have established the diameter of the stepped leader channel as being from 1 to 10 metres with most of the charge flowing in a central channel or core surrounded by a corona sheath. The return stroke was once thought to be several metres in diameter but following Bruce`s glow to arc transition theory and prediction of a small diameter core, experimental and observational evidence has established the core to be some 2 square millimetres in cross sectional area.

The return stroke may be the end of the dischage process but very often a second no-stepped leader will discharge along the ionised channel and initiates a second return stroke. Uman cites one lightning flash which repeated 26 times before ceasing.

A further phenomena, the M component, is a sudden increase in the luminosity of the entire channel following the return stroke.

Characteristics of an `average` lightning flash:-

Stepped leader takes 0.005 secs to develop.

Return stroke takes 0.0001secs (about 1/3 the speed of light).

Return stroke

200,000,000 volts potential over length.

Current 50,000 Amps.

Core temperature 25,000 C (about 5x hotter than surface of the Sun).

Length 5 miles.

There are 1200 thunderstorms per hour over the Earth`s surface. Each will have about 1,000 flashes of lightning. A thunder cell within a cumulo-nimbus cloud recharges in 30 seconds.

Empire State Building

Observations of lightning at the Empire State Building in the 1940s called into question the `common-sense` estimate of 2,000 million volts potential across a lightning discharge. Already it had been determined that a charge of 20 to 30 coulombs was being cancelled over an area of about 100 square km then the electrostatic field must be more in the range of 300 Volts per cm and not 10,000 Volts per cm predicted by the `common-sense` estimate. This put the potential in the region of 50 million volts and not 2000 million volts.

The top of the Empire State Building should have been at 2 million volts with respect to the ground level. But field values of 100 to 200 Volts per cm were recorded. Also many strokes were seen to be initiated upwards from the lightning conductors.

Dr.C.E.R. Bruce had been recommended to the Electrical Research Association by his mentor Sir Edmund Whittaker. He had worked on statistics and features of the arcs produced by circuit breakers on the National Grid. He was requested to investigate the earthing of the Grid steel pylons by a wire which was attached at the highest point and went from pylon to pylon. The idea was a common-sense one of a kind of continuous lightning conductor.

Bruce began an intensive study of lightning and looked at the results from Empire State Building. He considered the lower than expected field potentials and compared these with 10million volt flashes to transmission lines and moving film camera photographs and measurements of return stroke currents of 10 to 20,000Amps.

The diagrams show that the stepped leader advances in a thin channel which has a very luminous tip.

Bruce had his associates set up an experiment in which a steel gramophone needle represented the Empire State Building. A 2million volt spark was initiated from the needle to a metal plate 2metres above. From this Bruce determined the return stroke velocity to be about 30 million meters per second and also made an important observation about the pre-discharge condition.

The difficulty as he saw it was in trying to explain the spark assumption which required a build up to 2000 million volts before a lightning discharge. The simple spark discharge idea did not fit with the complex stepped leader process revealed by Boys and moving film cameras. The low measurements from the Building observations did not fit either.

A quick look at Volt Ampere characteristics: -

For a spark discharge the Volt Ampere Characteristic is Positive. That is as the voltage increase the current increases. In other words more volts give more amps in current.

For an arc discharge the Volt Ampere characteristic is Negative. That is as the current increases the voltage either diminishes or remains constant. More current for the same or less voltage.

71 To English

71 To Arabic-English

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[14] ) A.E Cartea and J.C.G de Jagera, aNational Physical Research Laboratory, Council for Scientific and Industrial Research, Pretoria, South Africa

[16] )

Zen Kawasaki, Koji Nomura, Sachiko Yoshihashi, Kenji Matsu-ura

Osaka University, Japan