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VOYAGER 1 OBSERVES LOW-ENERGY GALACTIC COSMIC RAYS IN A REGION DEPLETED OF HELIOSPHERIC IONS
E. C. Stone1,*, A. C. Cummings1, F. B. McDonald2,†, B. C. Heikkila3, N. Lal3, W. R. Webber4
Abstract
On 25 August 2012, Voyager 1 was at 122 astronomical units when the steady intensity of low-energy ions it had observed for the last 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.
E. C. Stone1,*, A. C. Cummings1, F. B. McDonald2,†, B. C. Heikkila3, N. Lal3, W. R. Webber4
Abstract
On 25 August 2012, Voyager 1 was at 122 astronomical units when the steady intensity of low-energy ions it had observed for the last 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.
Thirty-five years after launch, Voyager 1 is currently 18.5 billion km from Earth. The probe is still sampling the environment and communicating (a 17 hour journey) with NASA/JPL. What Dr. Stone (et. al.) are saying in the above abstract is that V1 is at the very edge of the solar system. The heliosphereic boundary. They report that energetic particles originating in interstellar space are on the increase while energetic particles emanating from the Sun are steadily decreasing (-1000x). Field lines are currently east/west but are expected to orient north/south at the breakthrough point. In short, V1 is on the cusp of breaking into true interstellar space. Theoretically, V1 has enough power to continue transmitting into the next decade. It is not clear what Voyager 1 will encounter next, as extensive computer modeling has thus far been inconclusive.
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