Teaching Astroparticle Physics Part1

MAGNETIC FIELD OF ASTROPHYSICAL OBJECTS AND COSMIC RAYS ENERGY

UNDERSTANDING THE "KNEE"

The plot of the Cosmic Ray Spectrum has a sudden change in the slope around c This variation, well visible in the figure below, is called the "Knee". A possible explanation is the leakage of particles from our galaxy. As you can discover with the app below, particles with energies exceeding 10¹⁶ eV have a radius of curvature in the galactic magnetic field which becomes similar to the thickness of the galactic disc and, as a consequence, they start to leak from the galaxy leading to a faster decrease in the spectrum.

With the blue slider, or writing in the momentum input box, you can change the order of magnitude of the momentum of the particle trapped in the galactic magnetic field and discover how the radius of curvature changes accordingly. You can explore the range in momentum from 10¹⁴ eV to 10²⁰ eV. Remember that for these values of the momentum the mass of the particle is negligible and you can consider Energy = Momentum.