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SCIENCE AT WORK SPECIAL REPORT FOCUS LAB WATCH Astrophysics Predicting Solar Flares BY FUI LEE LUK Solar flares have long been observed as bright flashes on the Sun’s surface, yet their origin is still somewhat obscure. Using satellite data and models, CPHT1 and AIM2 scientists have now unveiled the cause of these emissions of light, particles, and hot gas bubbles: the emergence, from inside the Sun, of a magnetic rope—a set of current-carrying magnetic field lines entwined like hemp rope.3 Flare study has so far been hindered by the difficulty of measuring the magnetic field in the Sun’s fiery corona (atmosphere) where flares erupt. But in 2006, breakthrough became possible when a Japanese satellite picked up data on the magnetic field of part of the Sun’s cooler photosphere (surface) where a flare was brewing. From this data, the team built two models. The first, which is based on equations governing magnetic fields, is like “an ultrasound of a flare’s pregnancy,” explains team leader Tahar Amari of the CPHT. Not only did it detect the growth of a magnetic rope a few days before the flare, but it also showed the rope’s magnetic energy swelling as it emerged from the Sun. Amari calls the second model “predictive” in that its numerical simulations forecast the result in the corona when the rope was at various stages of growth. It was when the rope exceeded given energy and altitude levels that it was freed from the Sun’s bonds and ejected as a flare. The researchers have developed “a useful method for space meteorology, namely flare prediction,” says Amari. This is especially important since solar interference can disrupt key infrastructures like power grids and GPS systems. PROFILE PORTFOLIO INNOVATION 1. Centre de physique théorique (CNRS / École Polytechnique). 2. Astrophysique, interprétation – modélisation (CNRS / CEA / Université Paris-VII). 3. T. Amari et al., “Characterizing and predicting the magnetic environment leading to solar eruptions,” Nature, 2014. 514: 465-469. tahar.amari@polytechnique.edu Archaeology A Puzzling Discovery BY EDDY DELCHER © F. D’ERRICO/PACEA/ CNRS PHOTOTHÈQUE 8 CNRS INTERNATIONAL MAGAZINE A 39,000-year-old cave wall engraving, interpreted as the first known example of Neanderthal abstract representation, has been discovered in Gorham’s Cave (Gibraltar) by an international research team.1 The invention of cave art has traditionally been attributed to modern humans, who settled in Europe around 40,000 years ago. The recent study,2 however, supports the theory that our distant cousins, the Neanderthals, produced abstract representations on cave walls and were indeed capable of abstract thinking, a major step in the evolution of our lineage. The cross-hatched engraving, whose overlaying sediments were dated by radiocarbon, was then analyzed by CNRS researchers Francesco 5 cm © RODRIGUEZ VIDAL ET AL. 2014 PNAS 1. De la préhistoire à l’actuel: culture, environnement et anthropologie (CNRS / Université de Bordeaux / Ministère de la Culture et de la Communication); Gibraltar Museum. 2. J. Rodríguez-Vidal et al., “A rock engraving made by Neanderthals in Gibraltar,” PNAS, 2014. 111(37): 13301–06. Model of the Sun’s magnetic field shows the presence, several hours before the flare, of a magnetic rope (gray) maintained in a state of equilibrium by magnetic loops (in orange). Analyses (a,b,c) show engraving episodes (gray) and breaks (white). Blue arrows indicate single-stroke lines, red arrows multiple-stroke lines in one direction. © T. AMARI / CENTRE DE PHYSIQUE THÉORIQUE


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