The scintillation, or intensity variation, of pulsars can be used to probe the interstellar medium on size scales similar to that of the solar system. Since scintillation is caused by multi-path scattering off of density variations in the ionized component of the interstellar gas, a detailed study of pulsar scintillation yields information about how the interstellar gas is clumped, whether or not it exhibits turbulence, and how the density variations are initiated and sustained. These questions are central to an understanding of the dynamics of our galaxy and, hence, of other spiral galaxies like ours. During the previous grant period, Dr. Daniel Stinebring discovered that a crisscross pattern that had been noticed for decades in dynamic spectra has a much clearer signature in transform space. His group has now studied this scintillation arc phenomenon extensively, using high dynamic range observations of pulsars, primarily obtained with the Arecibo radio telescope. The research carried out with this new award will explore this phenomenon in detail using high-sensitivity observations from the Arecibo radio telescope and other large telescopes. Detailed substructure, including inverted subarcs, will be explored fully and their timescale and frequency behavior will be determined. The goal of this work is to connect the detailed observations of scintillation arcs with the physical characteristics of turbulent gas in the ionized interstellar medium.
This research program will involve undergraduate students in the excitement of exploring a new phenomenon and piecing together parts of a bigger puzzle: how does large scale stirring of the interstellar gas create small scale turbulence which is eventually dissipated as heat? By working closely with Dr. Stinebring and his collaborators, the students will gain a broad range of technical skills as well as further develop their ability to independently explore problems. Using state-of-the-art electronics and computers at the largest radio telescopes in the world, the students will gain confidence in their ability to tackle large and complex problems. Opportunities to collaborate with scientists in the U.S. and abroad and to report their work at conferences and in publications will enhance students research experience and prepare them for graduate training or other roles in the technical workforce. ***
