Precision cosmic-ray detection with the Square Kilometer Array

What is the origin of the highest energy Galactic cosmic rays, ionized atomic nuclei that travel through space at nearly the speed of light? To answer this question we must detect them via the “air showers” of particles that are induced when cosmic rays interact in the atmosphere. Current experiments lack the precision needed to fully reconstruct air shower features and, consequently, to understand the cosmic rays themselves. Moreover, the hadronic interactions that shape air shower development take placeat energies beyond what we can reproduce in a laboratory setting and are not well understood. To solve this problem, we will revolutionize air shower detection by leveraging the Square Kilometer Array (SKA) radio telescope as the ultimate precision cosmic-ray detector.As the leader of the cosmic-ray detection groups at the LOFAR and SKA telescopes, I will capitalize on my expertise to implement cosmic-ray detection capabilities at the SKA. The instrument’s incredible antenna density will enable us to sample the air shower radio signal with order of magnitudes more detail than is currently possible, uniquely giving us access to fine details of the shower development. We will also install in-situ particle detectors with the capability to distinguish different air shower particles. By combining these data with radio observables, we can achieve comprehensive air shower reconstructions while refining hadronic interaction models—an essential step in advancing our understanding of high-energy cosmic-ray physics.We will use this novel technique to do the most precise air shower reconstructions ever made over a wide energy range, allowing us to distinguish cosmic-ray acceleration models and identify sources in the energy region where cosmic rays transition from Galactic to extragalactic origin. This project will lay the groundwork for decades of cosmic-ray science at the SKA, and yield the information we need to finally understand the elusive origins of cosmic rays.