Max-Planck-Princeton Center for Plasma Physics
The center fosters collaboration between scientific institutes in both Germany and the USA. By leveraging the skills and expertise of scientists and engineers in both countries, and by promoting collaboration between astrophysicists and fusion scientists generally, the center aims to accelerate discovery in fundamental areas of plasma physics.
A plasma is a gas of charged particles (ions and electrons). Most of the visible matter beyond the Earth is a plasma, including stars, the interstellar medium (matter between the stars) and the intergalactic medium (matter between galaxies). On Earth, plasmas are important for producing energy through fusion reactions, as well as many other technologies.
The goal of the center is to understand several fundamental problems in plasma physics. Solving these problems could lead to new breakthroughs in producing clean and reliable fusion energy, as well as help us to understand the Universe in which we live.
There are four primary research topics under investigation by members of the Center:
- Magnetic Reconnection
- Energetic Particles
- Plasma Turbulence
- Magneto-Rotational Instability
The MPS is particpating with three working groups.
1) Observations of prominence-cavity systems
Prominences are cool, over dense structures seen suspended in the lower corona above the solar limb. They mainly reside in highly tangled magnetic fields. Coronal cavities, regions of relatively low density, and high temperature, are often seen surrounding the cooler prominence plasma. The cavity structures often contain closed loops which surround the prominence. When the stability of the system is disrupted, the prominence and surrounding cavity material is ejected into interplanetary space as a Coronal Mass Ejection (CME). The aim of our research is to identify conditions leading to instability, by taking full advantage of modern high resolution imaging (e.g. Solar Dynamics Observatory (SDO) and STEREO) and spectroscopic (IRIS) observations of the Sun. The figure shows two views of a prominence-cavity system just after the prominence plasma was seen to rise up and start rotating, resembling a tornado. In this particular case the tornado-like activity was triggered by flares in the neighbouring active region (identified as AR).
Disk and limb views of a solar prominence on 25 September 2011 showing tornado-like activity: a) On the disk, prominences appear as long dark filament channels; b) The corresponding prominence structure seen on the limb. (a) was taken by STEREO-A at 195Å when it was 103° ahead of Earth, and (b) by SDO at 171Å. In (a) the dashed line is the position of the solar limb seen by SDO (Earth) and the long diagonal arrow is the projection of the position marked with a ‘+’ at the base of the prominence in the SDO image.
2) Field-aligned flows and currents on the Sun and in the laboratory
3) Magnetic reconnection at the Sun and in the laboratory
Due to the heat of the Sun direct, in situ observations of Solar reconnection are impossible. But reconnection can be studied in the laboratory, like in the MRX device of the Princeton University's PPPL and by the VINETA device in Greifswald (Germany). In the laboratory, however, the solar and astrophysical plasma conditions cannot be reproduced one-to-one.
The figure on the left illustrates the evolution of reconnection as the new connection between magnetic fields (black: field lines) through currents sheets (color coded current density) as it evolves with time starting from small natural fluctuations and turbulence and forming in the end macroscopic structures.
The figure below depicts the resulting three-dimensional structure of the magnetic field in reconnection regions. It deeply impacts the dynamical release of magnetic fluxes, generated, e.g., by dynamo processes below the surface of the Sun.
