CNRS researcher at Paris Observatory
Observatoire de Paris (LERMA)
61 avenue de l'Observatoire
75014 Paris, France
+33 (0)1 44 32 25 80
ludovic.petitdemange at obspm.fr
I am a CNRS researcher interested in understanding dynamo action occuring in astrophysical objects (stars and planets). I work at ENS-Paris in the LRA Laboratory which corresponds to LERMA Laboratory located at ENS.
I performed my PhD thesis in Astrophysics (ED127) at the LRA, Ecole Normale Supérieure
(Paris) in 2009 under the supervision of Emmanuel Dormy and Steven Balbus on "MagnetoRotational Instability and Planetary Interiors"
My research focus on magnetohydrodynamics and, in particular,
on numerical simulations related to MHD instabilities. I am interested in modelling the dynamics and generation mechanisms of natural dynamos. I do my best to understand the physical mechanisms which affect the magnitude, the topology and the time variations of stellar and planetary magnetic fields.
The MagnetoRotational Instability (MRI) is a fluid instability arising
in MHD flows when the angular velocity decreases outward and a
magnetic field is applied. It is currently the best candidate to
explain angular momentum transport in accretion disks around stars and
black holes. Indeed, the MRI explains how a weak magnetic field can
destabilize otherwise stable Keplerian flows. Despite its simplicity,
several theoretical aspects of this instability are still poorly
known, like the mechanisms of saturation of the MRI, the emergence of
non-axisymmetric modes or the interaction with dynamo fields.
It is strongly believed that magnetism of planets, stars
and galaxies is
due to the self generation of a magnetic field by the turbulent
motion of an electrically conducting fluid. However, a lot of questions
remain unsolved: what are exactly the mechanisms of the field
What determines the complex dynamics of the field, like periodic
oscillations or chaotic reversals? What is the role of turbulence
or how saturation of the field occurs ?
A lot of characteristics of dynamo or MRI experiments remain not fully
explained, and it can be very useful to use the numerical approach to
understand what happens in these experiments. In this perspective,
I use numerical simulations in different geometries to model dynamo action or MHD Couette flow in laboratory.
is a unique opportunity to test directly the validity of numerical
models against experimental data.
See more about my research ....
Download my Ph.D. Thesis (pdf)