Hydrodynamic Effects in Plasma, Combustion and Astrophysics
We work on hydrodynamic phenomena in plasma physics, combustion and astrophysics
The whole modern technical civilization is based on combustion as the main source of energy. It is also one of the most interesting subjects of nonlinear science being extremely rich of different nonlinear effects such as instabilities, turbulence, fractals, etc. Besides, collective hydrodynamic effects of the same type play play an important role in plasma physics and astrophysics, e.g., in inertial confined fusion, quantum plasma and plasma in organic semiconductors.
Participating departments and units at Umeå University
Collective hydrodynamic effects are important for many problems in plasma physics. In this project, we focus on hydrodynamic and magnetohydrodynamic phenomena in inertial confined fusion, quantum plasmas and plasmas in organic semiconductors.
Concerning inertial confined fusion, we study mostly the hydrodynamic instabilities like the Rayleigh-Taylor (RT) and Darrieus-Landau (DL) instabilities. The RT instability is extremely important in many problems. Within the inertial confined fusion, the RT instability is the main obstacle in obtaining high density of a thermonuclear target and igniting the reaction. The RT instability develops when high density plasma is supported by low density plasma in a gravitational field. Due to the Archimedes force, potential energy stored in the heavy plasma is transformed into kinetic energy of the flow. The gravitational field may be real or "effective" like in inertial confined fusion, where laser-heated light plasma compress and accelerated the heavy target. In the reference frame of the target, the acceleration works as the gravitational filed pointing from the heavy plasma to the light one, which leads to the RT instability. As a result of the instability, thin jets of heavy plasma "fall down", while laser heated plasma moves "up" in the form of a large bubble. Within this project we will study nonlinear development of the RT instability in the laser-plasma system. The RT instability in plasma produces also an extra-strong magnetic field, which has been observed in recent experiments. The other instability of interest, the DL instability, develops in plasma with energy sources like laser energy in inertial confined fusion. Energy spreads due to thermal conduction in the form of a front, which is called a deflagration front. The most typical example of a deflagration front is the usual flame. The DL instability is inherent to all deflagration fronts; the instability bends a front and increases the propagation velocity.
Another important area of the project is hydrodynamics of quantum plasma. Quantum effects influence plasma dispersion due to finite size of electron wave-function and and because of Fermi pressure. These effects become especially important in high densities and/or low temperature plasmas as well as in other quantum systems like Bose-Einstein condensate and in nonlinear optics. Quantum hydrodynamics is a fast developing research area in plasma physics with large number of potential applications, e.g., in electronic nanoscale devices. In quantum hydrodynamics we plan to study shocks and hydrodynamic instabilities. Structure of quantum shocks differs considerably from the classical case.
We also plan to study dynamics of complex plasma in organic semiconductors, which includes diffusion and mobility of electrons, holes, positive and negative ions. The project focuses on propagation of doping fronts in p-n junction. Experiments demonstrate that the fronts are unstable, and the instability is similar to the DL instability of flames and ablation in inertial confined fusion, though it happens on other length and time scales.
These problems of plasma hydrodynamics involve similar nonlinear effects and, therefore, they require similar methods of solution, both theoretical and numerical.