Most of the observable matter in the Universe, over almost all of the history of the universe, has been in the plasma state. In this state, normal atoms have had some or all of their electrons ripped away because of intense heating or collisions. On the largest scales, matter is dominated by gravity, but on smaller scales, those charged ions interact with each other and with electric and magnetic fields to help create structure and channel momentum and energy. In its broadest sense, plasma astrophysics aims to study and help understand how plasmas behave in order to understand the detailed birth, evolution, and death of the wide variety of structures we can see in the universe: from stars and planetary systems, to galaxies and clusters of galaxies.
The interests of plasma astrophysicists here at UW-Madison mirror this wide range of topics. For instance, we study how plasmas behave when falling into the gravity well of black holes, and also how plasmas are ejected at high speeds from stars, black holes, and galaxies. We also are strongly interested in understanding the origin and evolution of magnetic fields on scales from individual stars to clusters of galaxies. In addition, for many years at UW-Madison, observers have been studying plasma between stars and galaxies; plasma astrophysicists are working to understand the role of turbulent motions in this diffuse plasma, as well as the importance of magnetic fields and relativistic particles in organizing structures and powering outflows on galactic scales.
In this work, astrophysicists often collaborate with physicists who work on similar problems in fusion science. In particular, at UW-Madison, plasma astrophysicists within the Astronomy Department have close connections with plasma physicists in the Physics Department. Our campus is also an integral part of the Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, which allows and encourages work with plasma physicists across the country and the world.