Philippe Jeanjacquot philippe.jeanjacquot@ac-lyon.fr Professeur de Sciences-Physiques Lycée Charlie Chaplin, Décines Gérard Vidal Directeur de collection ENS de Lyon/Ifé 2015-11-12 Cette œuvre est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d’Utilisation Commerciale - Partage dans les mêmes conditions 4.0 International How to build with the equipment of your school a model of the earth with the aurora light. When someone has the chance to see an aurora borealis, he is submerged by the beauty of such a phenomenon. How nature can it create such a spectacle? One wants to include/understand what hides behind the aurora borealis. Why not use the auroras to give desire of doing sciences? But this phenomenon appears only in the areas of high latitudes. The photographs, the films cannot replace reality and the emotion which it causes. Would it be possible to reproduce these polar lights in a laboratory and why not with material of high school? To benefit from it thus to include/understand and explain the implied scientific phenomena? If one considers the history of sciences, one discovers the stages, the hesitations, the errors and the projections in the comprehension of the polar lights. But especially a treasure, a beautiful experiment is discovered: the experiment of Birkeland. Can one remake it with the means of the high school? Can one capture the polar lights? It is the challenge which we launched out. Initially, a thorough knowledge of the subject was essential. Then, a long series of experiments, for finally analyzing our results and including/understanding our errors. With time and patience, we could carry out our project. To simplify and improve certain parts of the experiment. The experiment is made to be presented in front of any type of public. It was presented at the high school within the framework of the week of science. It was presented in front of three preparatory classes at large schools (PC*) at the high school Lamartinière Montplaisir. It will be presented in front of pupils of college and primary school in Turkey within the framework of a Comenius project. According to the level of the public, the history of sciences, various physical phenomena, solar meteorology, plasma physics can be approached.

Cette vidéo est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. Image : Philippe Jeanjacquot, ACCES 2016 ENS de Lyon Cette vidéo est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. Image : Philippe Jeanjacquot, ACCES 2016 ENS de Lyon Link to the video on line

The sun produces particles uninterrupted. They create a “solar wind”, it is a balanced mixture of protons and electrons with 5 to 25% of Helium cores. The wind blows permanently with a speed of 200 with 700km/s. When this solar wind meets the magnetic field, the particles which it contains follow the lines of magnetic field which lead them to the poles. Two ways are possible: first is direct, they are the polar horns. the second circumvents the magnetosphere. The particles are found then in a neutral layer then are accelerated towards the Earth. This phenomenon creates the auroral rings. These particles then will run up against the gas molecules of the Earth's atmosphere. These molecules are of this fact excited and produce light when they become again stable. This phenomenon is not only on Earth but also on the other planets of the solar system which have a magnetic field. (Jupiter, Saturn, Uranus, Neptune) The auroral rings were observed for the first time since space by the satellite “Dynamic explorer” of 1981 to 1990

Explanations relating to the various components of the system: The vacuum bell-jar and the pump are used to reproduce the conditions of pressure necessary to the appearance of the polar lights. The generator high-potential makes it possible to send the electrons in the bell and to replace the particles coming from solar wind. The sphere is magnetized, it represents the Earth and its magnetic field. We have two magnets to reproduce the magnetic field. Cathode sends the electrons replacing solar wind. (cathode represents the tank of particles charged about which we spoke in the I2 paragraph) it is the neutral layer. That is there, the polar lights were captured. And even if they are not on the same scale that the true ones, they enable us to show and study easily this very spectacular phenomenon. The experiment also enables us to make other analogies with space electromagnetic phenomena. One realizes as well as the electromagnetic forces are far from being negligible when astronomy is studied. Science at school, issue 26, auroraeInternational Science at school, issue 26, aurorae (how to build the experiment) Jean Lilensten's website about the experiment for the university, the Planeterrella Spaceweather website European space weather website “Norwegian Forwarding 1899-1900” K. Birkeland, “The Northern Light Their Heritages and to their Science” Asgeir Brekke and Alv Egeland. “Of the Sun to the Aéronomie Earth and meteorology of the space” Jean Lilensten. “Kristian Birkeland have I knew him” Olaf Devik “Severe Space Weather Vents--Understanding Societal and Economic Impacts Workshop Carryforward DEC 2008” (American Academy of Science)

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 1995 Philippe Jeanjacquot

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 1995 Philippe Jeanjacquot

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 1995 Philippe Jeanjacquot

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 2008 Philippe Jeanjacquot

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 2008 Philippe Jeanjacquot

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 2008 Philippe Jeanjacquot

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 2008 Philippe Jeanjacquot

Cette image est mise à disposition selon les termes de la Licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International. 1995 Philippe Jeanjacquot The first shere on the left is the model of the Earth with the Auroral ring and the Van Allen Belt, the other sphere on the right is the model of the Sun with a coronal ejection on the equator.