Plasmas support a large variety of waves, some familiar to all such as light and sound waves, but a great many exist nowhere else and one of the fundamental waves in magnetized plasma is the shear Alfvén wave, named after Nobel Prize winning scientist Hannes Alfvén, who predicted their existence.
Shear waves of various forms have been a topic of experimental research for more than 15 years in the Large Plasma Device (LAPD) at the University of California, Los Angeles. When the waves were first studied, it was discovered that their creation gives rise to exotic spatial patterns, such as the one below, all of them Shear Alfvén waves.
Three-dimensional data, such as the magnetic field of the wave shown here, will be presented along with relevant theory in a presentation at the 52nd annual meeting of the APS Division of Plasma Physics. Part of the presentation will be in 3D.
Representation of the three-dimensional magnetic field (due to four currents threading the center of each helix) of a shear Alfvén wave, acquired at an instant of time throughout the volume of a large (60 cm diameter ,18m long) plasma in the LAPD device at UCLA. The currents and the field topology change in fractions of a millionth of a second. The sparkles are proportional to the electric field in the plasma induced by the wave. Credit: Walter Gekelman, UCLA
It has become accepted that Alfvén waves are important in a wide variety of physical environments. They play a central role in the stability of the magnetic confinement devices used in fusion research, give rise to aurora formation in planets, and are thought to contribute to heating and ion acceleration in the solar corona. Shear waves can also cause particle acceleration over considerable distances in interstellar space.