The Construction of a Pulsar Interstellar Medium Array Detector

Interstellar space is filled with a rich medium of gas and dust. Most astronomers take images of large structures in the interstellar medium (ISM). However, observations of radio waves from pulsars traveling through the ISM allow access to much smaller scales. These pulsars act as probes within the Galaxy's active environments. Astronomers use pulsars to understand turbulence in the ISM, identify clouds and filaments, and even understand the wind of particles streaming from the Sun. The investigators will combine observations of hundreds of pulsars by many telescopes around the world. These will be combined to create Galaxy-sized detector known as a "Pulsar ISM Array." This work will connect pulsar astronomers around the world with many other communities to create a detailed picture of our dynamic Galaxy. The investigators will also build classroom laboratory and outreach demonstrations. These will engage students and the public in understanding the complex phenomena of the ISM. The investigators will construct a "Pulsar ISM Array" (PISMA) analogous to a pulsar timing array (PTA) used in the study of low-frequency gravitational waves. Since all pulsar emission is dispersed by the ISM, all pulsars can contribute to the PISMA and not just the ultra-precise ones used in PTA experiments. In combining a wide-range of observables, including but not limited to pulsar dispersion measures, scintillation parameters, flux-density variations, secondary spectra, along with non-pulsar observables such as sky maps from H-alpha surveys, the PISMA will provide key insights into understanding the processes that govern the transfer of turbulent energy from kiloparsec to sub-AU scales; the formation, morphology, and population of compact plasma structures and larger-scale over-densities; and the extreme environmental conditions around pulsars themselves. Advancing understanding in these areas will also benefit understanding in the broader astronomical communities researching Fast Radio Bursts and extragalactic transients, space weather, and intraday variability of radio quasars, and provide input into the most sophisticated Galactic electron density maps yet created. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.