* Symposium web page:* www.iutam2012.info

A diverse variety of fluid systems are characterised by extreme events that are localised in space and time and are often associated with intense energy exchanges that dramatically alter their global behaviour.

For example, in the atmosphere, extreme events include cyclones, perfect storms and mountain winds and can directly disrupt agriculture, transportation and industry. In the oceans, the so-called rogue waves are sudden, high-amplitude waves that can even destroy large ships but whose nature is not fully understood. And in the interplanetary medium between the Earth and the Sun, magnetic storms of highly energetic, ionized particles can disable communications satellites.

Extreme events can also dominate aspects of the fine-scale dynamics of the underlying equations of classical turbulence, quantum fluids, and magnetohydrodynamics. It has been shown that the carrying fields (vorticity, wave function and magnetic induction) first develop anomalous values that are localised in sheets and tubes, then become subject to intense reconnection events. Reconnection is usually associated with the release of energy, but numerical results show that around the instant of reconnection very little energy is directly released. We would like to know whether these events are directly associated with cascades of energy, dissipation or the release of material, or are they simply a signature of more fundamental underlying dynamics?

NOVELTY:

We propose to gather together experts from different disciplines of science about a common subject: Extreme Events in Fluids. The idea is to generate fruitful discussions and produce transfer of knowledge amongst the disciplines, via the following instances:

- 9 plenary sessions of one hour duration, on:Euler and Navier-Stokes Turbulence.Waves and Atmosphere.Fundamental Systems: Pure Maths' Viewpoint.Magnetic Fluids.Quantum Turbulence.

- 4 Quaker meetings (i.e., discussion sessions) of one hour duration, which will help reinforce and materialise the understanding of the common aspects of extreme events in the different disciplines.

- 50 regular lectures of 20 minutes duration, on relevant topics where extreme events play a part.

- Poster sessions where young researchers, postdocs and PhD students can showcase their findings and improve their scientific networks. We have made sure that the amount of young researchers, postdocs and PhD students represent at least 20% of the total number of participants.

Sample of topics: Atmospheric dynamics (e.g., fronts, jets and hurricanes).Oceans (e.g., rogue waves).Euler and Navier-Stokes classical turbulence (e.g., near-singular behaviour). Magneto-Hydrodynamics (e.g., magnetic reconnection).Superfluid quantum vortices (e.g., change of topology of vortex tangles, experimental BEC Turbulence).Optics (e.g., rogue solitons).

Due to the local spatio-temporal nature of extreme events in fluid systems, one can divide their progression into the following phases: genesis, development, maturity or developed phase, and decay. During the developed phase, the statistical description appears to be independent of the original mechanisms that generate these events. The same could be said, to some extent, about the geometry and other features of the developed structures. With this insight, it seems possible that by understanding extreme events and the dynamics of their equations better, we could improve our ability to make advances in global weather predictions down to the scale of 50 kilometres, noise from turbojet engines, fusion reactors and space weather. All of which continue to be just outside our reach even though many should be accessible with current computing architectures if the old paradigms held.

This Symposium will gather more than 50 researchers from different scientific disciplines where extreme events are relevant. They will be guided primarily by the plenary presentations of 9 plenary speakers, all world experts in their respective fields.