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/ Department of Physics

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Experts in: Numerical simulation

CHARBONNEAU, Paul

Professeur titulaire

The solar magnetic cycle is both the driver and energy source of all of solar eruptive phenomena with impacts on Earth, whether it has to do with space weather, damage to technological infrastructures or perhaps even impacts on Earth's long-term climate. The work of my research group aims in part at better understanding the physical mechanisms driving the solar magnetic cycle, including the significant fluctuations observed in the duration and amplitude of individual cycles. The unifying physical principle underlying all the phenomena that we model lies in the complex nonlinear interactions between the solar magnetic field and internal plasma flows in its outer layers.

We recently achieved a world first: a global magnetohydrodynamical convective dynamo simulation producing a large-scale magnetic field showing a very solar-like spatiotemporal evolution, including, in particular, regular polarity reversals taking place on a multi-decadal timescale. We are also developing novel computational approaches to modelling the photospheric impacts of the solar magnetic field, which allows us to couple solar-cycle models to reconstruction schemes for describing variations in spectral irradiance and solar luminosity during the activity cycle, a key step in better quantifying possible influences of solar activity on climate change.

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Lewis, Laurent J.

LEWIS, Laurent J.

Vice-recteur associé, Professeur titulaire

My research program examines the general theme of computational physics of materials. We use powerful computers to probe the structural and other behaviour and properties of materials, and the "structure-function" relationship. Our preferred approach is molecular dynamics, which involves integrating the equations of motion of a system of atoms under the effect of forces from "potentials"; they may be generic (Lennard-Jones, for instance), empirical or semi-empirical, or even ab initio. The size of the systems depends on the potential used and varies from tens or hundreds of atoms to several million.

We study a vast range of problems, but we are particularly interested in the following ones, just as an example: (i) laser ablation and laser-material interactions; in this case we are trying to understand how matter reacts to powerful, short laser pulses - ejection mechanisms, structural modifications of the target, properties of the ablation plume, etc. (ii) disordered, amorphous or vitreous materials; in this field, we are trying to understand the short-, medium- and long-term structure of materials like amorphous silicon, metallic glass, etc. (iii) thermal properties of nanoscopic materials; we are trying to determine how heat dissipates near nanometric structures and how it moves in molecular junctions between nanoparticles, in particular.

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