The lightning in ball

The the lightning swell of it, or globular Foudre, is a rare weather phenomenon and still insufficiently explained. It would be appeared as a luminous sphere of a score centimetres in diameter which appears during a Orage. Current knowledge about it is very fragmentary: it could be reproduced in experiments only very recently. It would be in relation to the vaporization of a quantity of Silicium, the chemical element more running to the surface of the Earth. Hitherto, one could be based only on testimonys whose validity was necessarily prone to guarantee. The various accounts seemed however sufficiently coherent to allow a study of the phenomenon.

Description

The appearance of the lightning in ball can take place after that of a flash. It is generally yellow drawing towards the red even if it can be blue, green or white. It is often accompanied by cracklings or a whistle after the Tonnerre and by an odor of Ozone, Soufre or nitric oxide. Its diameter generally varies from 20 to 40 cm and its lifespan varies between 1 and 30 seconds. It can remain motionless or move horizontally at a speed of a few meters a second, with a rotation movement on itself. The balls of the lightning show often sensitive to the electromagnetic fields, attracted by wire and the electrical outlets. A fireball can die out in two manners. The first mode explosive, fast and is accompanied by a violent noise. The second is a quiet extinction of which the duration is variable. Its luminosity can be very strong or on the contrary weak, while its temperature can reach the 10 000°C. However, in the wake of the ball, the temperature does not exceed 60 °C, according to certain testimonys. Witnesses even pay to have seen some crossing planes or of the windows or walls.

Theories

Concerning this phenomenon, one has very little knowledge, based mainly on testimonys. One thus does not know yet how the lightning swell about it is created, but there exist various theories.

First of all, the theory of the chemical model explains why, since the fireballs appear in general during a violent one storm, an impact of the lightning takes place. By striking the ground, it vaporizes particles of Silicium burning, of Oxygène and Carbone which joins between them to form long chains. These filaments which burn slowly tend to be folded up on themselves to form balls (cf analogy with the Polymère S). These particles, of micro size even nanometric, are negatively charged. Those can then form a sphere which slowly will oxidize with the air. This theory was advanced by John Abrahamson and James Dinniss of the university of Canterbury in New Zealand, whose work was pousuivis by Antonio Pavo and Gerson Paiva, two researchers of Université Fédérale of Pernambuco to the Brésil who recently succeeded in producing the phenomenon by vaporizing a mean silicon substrate using an electric arc of 140A.

Put aside the chemical model, there exists the theory of plasmas. The fireball would be filled with plasma. This last is formed starting from an ordinary gas whose heat causes the expulsion of one or several electrons of several Atome S. These atoms are then ionized, and it is said that the state plasma is reached when sufficient atoms was ionized. The ball of plasma would be traversed by threads of current buckled on themselves and interpenetrating in order to confine the ones the others by the magnetic fields which they create. This is made possible for very high temperatures (30 000 °C), which is largely obtained after the passage of a flash. Once created, the ball dissipates its energy in thermal and luminous form. That decreases its temperature, until the conductivity of plasma is too low to ensure stability. The fireball then finishes its existence while disaggregating.

In both cases it is considered that the persistence of the lightning in ball would be maintained by the strong electromagnetic radiations of the lightning.

Culture

Adventures of Tintin and Milou : the 7 crystal balls contain a long reference to this phenomenon.

Testimonys

We know all of close testimonys. The incidents caused by the lightning in ball are often described of long time in meticulous reports/ratios of gendarmerie. Here are some: " One day, not far from Secondigny (Two - Sevres), two young children of twelve and fifteen years played on the road, when suddenly they transfer to roll in front of them a fireball of the size of an orange. The machine was charming and of inoffensive appearance. One of them, to have fun, touches the sphere of the end of its foot; at once, a terrible explosion is made hear. The imprudent young person will be killed Net, and his thrown comrade with ground, but without gravity. "

" August 28th, 1839, during a violent one storm above Paris, the lightning fell in the middle of the court from the granting. It had the shape of a large sphere of fire. It dug a depression of 18 cm daimeter, then flashes back to fall further 3 meters, where it always violently made a new hole 9 centimetres in being agitated diameter. This sphere of fire jumped on the surrounding wall, of which it followed the hood on 30 meters… "

" I am in flight in Navajo (pilot of business aircrafts), nonpressurized, therefore with an altitude of cruising as weak as possible for the comfort of the passengers, (7 000pieds - 2.000 m) moreover time is rather stormy, some flashes streak the landscape, we fly under a very dark vault of clouds above the valley of the Rhone course to the South bound for Marseilles. Around Aubenas I suddenly saw “falling from the sky, crossing the clouds” a fireball whirling slightly while falling relatively gently. Nothing to see with the instantaneous flash of a flash. I followed his trajectory and I saw it bursting while arriving on the ground in a small sheaf. I could still observe the ground a few seconds after this impact and I did not note anything of other, this ball had apparently not caused a departure of incendie."

See too

External bonds

a page on the site of the ENS of Lyon
Reproduction of the phenomenon in laboratory (Eli Jerby)

Random links: