Voyager 1 Observes Low-Energy Galactic Cosmic Rays in a Region Depleted of Heliospheric Ions

On 25 August 2012, Voyager 1 was at 122 astronomical units when the steady intensity of low-energy ions it had observed for the previous 6 years suddenly dropped for a third time and soon completely disappeared as the ions streamed away into interstellar space. Although the magnetic field observations indicate that Voyager 1 remained inside the heliosphere, the intensity of cosmic ray nuclei from outside the heliosphere abruptly increased. We report the spectra of galactic cosmic rays down to ~3 × 10⁶ electron volts per nucleon, revealing H and He energy spectra with broad peaks from 10 × 10⁶ to 40 × 10⁶ electron volts per nucleon and an increasing galactic cosmic-ray electron intensity down to ~10 × 10⁶ electron volts.