Magnetic reconnection is a phenomenon of nature in which magnetic field lines change their topology in plasma and convert magnetic energy to particles by acceleration and heating. It is one of the most fundamental processes at work in laboratory and astrophysical plasmas. Magnetic reconnection occurs everywhere: in solar flares; coronal mass ejections; the earth’s magnetosphere; in the star forming galaxies; and in plasma fusion devices.
A field of physics that is growing in interest worldwide that tackles such astrophysical phenomena as the source of violent space weather and the formation of stars.
One of the most fundamental tenets of astrophysical plasma physics is that magnetic fields can be stretched and amplified by flowing plasmas. In the right geometry, this can even lead to the self-generation of magnetic fields from flow through the dynamo process, a positive feedback instability where seed magnetic fields are stretched and amplified by flow in such a way as to reinforce the initial seed. This happens only when plasma is highly conducting, fast flowing, and when the magnetic field is weak. Laboratory plasmas exploring this parameter regime are surprisingly rare.
In 2005 a novel imaging spectro-polarimeter, the Coronal Multi-channel Polarimeter (CoMP), was deployed to the Evans Facility in Sunspot, NM to measure the solar corona’s magnetic field. The design of the instrument permitted it to capture something quite unexpected – the ubiquitous Alfvénic motion of the coronal plasma. Shortly thereafter the NASA/JAXA Hinode mission observed the roots of the Alfvénic motion in the complex chromospheric boundary region between the Sun’s surface and the corona.
11th International Workshop on the Interrelationship between Plasma Experiments in Laboratory and Space (IPELS)
Three teams led by scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have won major blocks of time on two of the world’s most powerful supercomputers. Two of the projects seek to advance the development of nuclear fusion as a clean and abundant source of energy by improving understanding of the superhot, electrically charged plasma gas that fuels fusion reactions.
The physics of condensed matter provides a unique perspective on materials and systems of environmental relevance. I discuss three ways in which concepts and methods of condensed matter physics bear upon the quest for a sustainable future. Electronic devices made from metal oxides may enable new approaches to renewable energy, such as diodes that operate at optical frequencies to directly convert the electromagnetic field of sunlight to current.
Thirty-five years after their launches in 1977, the twin Voyager spacecraft have completed the Grand Tour of the outer planets and are now exploring the outer regions of the heliosphere. Soon they will be the first man-made objects to enter and explore interstellar space. Voyager 1 crossed the termination shock of the solar wind on December 16 2004 and Voyager 2 crossed the same structure on August 30 2007. The next destination is the heliopause, the boundary between plasma and magnetic fields from the Sun and plasma and magnetic fields from our galaxy.
Hantao Ji is a professor of Astrophysical Sciences at Princeton University and a Distinguished Research Fellow at PPPL. For more than 20 years he has been interested in the growing fields of plasma physics and astrophysics, and has dedicated his career to bringing them closer together.
Looking backwards, using fossil evidence from nearby galaxies provides a plausible picture of how galaxies have formed over cosmic time. Also, going forwards, the present quite definite cosmological model, shows how perturbations grew from low amplitude fluctuations via standard physical processes to the present world. Finally, we can employ large telescopes as a time-machines – directly observing the past history of our light-cone. While none of these approaches gives results accurate to more than 5-10%, a plausible picture emerges. Massive galaxies form in two phases.
Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.
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