The Principal Investigator (PI) will study solar coronal phenomena using laboratory experiments in a plasma chamber. The chamber will create plasma regimes relevant to the solar environment, and these plasma configurations will undergo complex morphological changes that depend on imposed boundary conditions, such as the normal magnetic field, current density, and plasma mass flux. By controlling these boundary conditions, the PI will create plasma loops that simulate actual phenomena on the Sun, such as single loops, a single loop interacting with an externally produced magnetic field, or two loops undergoing localized three dimensional magnetic reconnection. The PI's apparatus uses advanced diagnostics, including high speed digital imaging, spectroscopy, laser interferometry, multi-element magnetic probes, and a pinhole x-ray camera, to observe and record various plasma states and physical parameters during his experiments. The PI will compare his measurements to the predictions of theoretical solar coronal models in order to improve, modify, or challenge them. This is possible because his experimental plasmas are governed by similar physics to the solar corona case, and in particular, to the physics of plasma upflows from photospheric footpoints and of the collimation of plasma-filled, twisted magnetic flux tubes like those seen on the Sun.
The PI will disseminate his research results by communicating directly with the solar physics community via talks, publications, and participation in the annual workshops. His experiments may provide new interpretations of recent and unexplained spacecraft observations, and provide rich educational material through colorful graphics and movies derived from his plasma chamber's diagnostic measurements. The PI has a record of mentorship of young women in physics, and plans to continue that here by increasing the number of female PhD scientists trained in plasma physics through these experiments.
The goal of this project is to learn more about the fundamental physics governing the evolution and dynamics of structures in the solar corona. These structures typically have an arch shape and consist of twisted magnetic flux tubes filled with plasma. The twist is a consquence of electric current flowing along the flux tubes. Interaction between the electric current and the magnetic field produces forces that act to push or pull on the arched flux tube. One type of force tends to expand the arch and can lead to eruption of the arch while another type of force is restraining and opposes eruption. The project uses experimental techniques to produce transient arched plasma loops in a controlled laboratory setting. These laboratory loops are about a billion times smaller than solar loops and change a billion times faster but are governed by essentially the same equations as actual solar loops. Thus, the behavior of the lab loops to a large extent mimics the behavior of solar loops. By careful control of the magnetic field and current in the lab loops, the threshold condition for eruption is being investigated. This threshold involves the expansion forces suddenly overwhelming the restraining forces. In a related experiment, two arched flux tubes that are oblique to each other are allowed to cross over and merge at a point to form a single long flux tube and also a single short flux tube. Both the merging process and the breaking off that occurs during eruption involve a sudden change in the magnetic connectivity that is analogous to a railroad line changing connectivity when the tracks are switched at a junction. The sudden change in connectitivity is called magnetic reconnection and involves highly localized rapidly changing magnetic fields. This process is believed responsible for the generation of energetic particles when solar structures erupt because fast changing magnetic fields produce large electric fields that then accelerate charged particles. Supporting theoretical studies are underway on how magnetic reconnection is closely related to certain kinds of plasma waves. It is predicted in particular that magnetic reconnection will radiate whistler waves in contexts where the reconnection region is very thin and reconnection is very fast. Experimental investigations are underway for whistler waves excited by magnetic reconnection.
