Aurora observations,1726. Artwork of an aurora seen at Breuillepont (near Paris),France,on 19 October 1726. Aurorae,displays of coloured lights in the sky,form as charged particles in the solar wind are drawn by Earth's magnetic field to the poles. There,they collide with gas atoms and molecules,causing them to emit light. Auroral displays outside the polar regions are usually due to a rise in solar activity. This view,looking north towards the horizon,is labelled with the celestial compass points (capital letters). Artwork published in Traite Physique et Historique de l'Aurore Boreale (1754) by the French geophysicist Jean-Jacques d'Ortous de Mairan (1678–1771) |