Astrophysics & Particle Physics-APPC 2026

Cosmic Rays are high-energy particles, primarily protons and atomic nuclei, that travel through space at nearly the speed of light. They originate from a variety of astrophysical sources, including supernova remnants, neutron stars, active galactic nuclei, and gamma-ray bursts, and are a central subject in astroparticle physics.When cosmic rays enter Earth’s atmosphere, they interact with molecules to produce secondary particles, creating extensive air showers detectable by ground-based and space-based observatories. The study of these interactions provides insights into the properties of high-energy particles and the physics of particle acceleration in extreme environments.Cosmic rays are classified into galactic and extragalactic populations. Galactic cosmic rays primarily originate within the Milky Way and are influenced by magnetic fields, while extragalactic cosmic rays come from distant galaxies, traveling across intergalactic space before reaching Earth. Their energies can range from a few megaelectronvolts (MeV) to ultra-high energies exceeding electronvolts.Observations of cosmic rays help scientists study the interstellar medium, magnetic field structures, and shock acceleration mechanisms. Instruments like the Pierre Auger Observatory, AMS-02, and IceCube detect cosmic rays and their secondary products, providing vital data on energy spectra, composition, and directional origins.Cosmic rays also affect space weather, influencing planetary atmospheres, satellite electronics, and astronaut safety. Studying cosmic rays contributes to understanding fundamental physics processes, including particle acceleration, interactions at extreme energies, and the propagation of high-energy particles across cosmic distances.By investigating cosmic rays, astronomers and physicists explore high-energy astrophysical phenomena, stellar explosions, and the dynamics of the universe, linking observational data with theoretical models. Cosmic rays remain a vital probe of the most energetic and extreme processes in the cosmos, bridging astrophysics, particle physics, and space science.