Why do cosmic rays usually not travel in straight lines through the Milky Way Galaxy?

Cosmic rays, which consist of high-speed atomic nuclei and electrons, do not travel in straight lines through the Milky Way Galaxy because they are electrically charged particles moving through the galactic magnetic field.123

When a charged particle moves through a magnetic field, it experiences a force that is perpendicular to both its direction of motion and the direction of the magnetic field. This force causes the particles to follow curved, spiral, or helical paths rather than straight lines. Because their trajectories are constantly deflected by these magnetic fields, it is generally difficult to determine the precise origins of cosmic rays by simply tracing their arrival directions back to a source.4235

In contrast, neutral particles like gamma rays are not affected by magnetic fields, allowing their paths to point directly back to their cosmic origins.5