Milky Way passes the baton: seamless transition of cosmic rays ✦
Original: "Elemental cosmic ray spectra reveal two populations of Galactic sources and an immediate transition to an extragalactic component after the knee"
A new analysis of protons, helium, and iron shows that galactic accelerators run out of steam at the PeV knee, and beyond that extragalactic sources seamlessly take over.
Links in the knowledge graph 1
At the 3 PeV mark, the galactic orchestra falls silent—but there is no silence. Extragalactic sources pick up the melody without delay, as if the conductor passed the baton and the new ensemble is already playing. It was long thought that our Milky Way had the solo up to 4 EeV. Now it's clear: the finale comes earlier, and cosmic rays with the highest energies are visiting performers from the distant universe.
🎯 A proton with an energy of 1 EeV in a typical galactic magnetic field (3 μG) has a Larmor radius of about 300 parsecs—almost half the disk thickness, so the Galaxy cannot contain such particles, and they almost certainly come from beyond its borders.
\frac{dN}{d\varepsilon} = K \varepsilon^{-\gamma + b \ln(\varepsilon/\varepsilon_r) \ln(\varepsilon/\varepsilon_c)} \exp(-\varepsilon/\varepsilon_c)
Modified power-law spectrum with curvature, describing accelerated protons in supernova remnants up to the maximum energy.
J(E) = F_1(E) + F_2(E) + F_3(E)
The total differential cosmic-ray flux at Earth is the sum of a low-energy galactic (F1), high-energy galactic (F2), and extragalactic (F3) components.