Anomalous Cosmic Rays

Outcome: A new origin of anomalous cosmic rays measured by Voyagers was proposed. It is related to acceleration of particles in sites of reconnection.

Transformative: This may be the first indication that the process of cosmic ray acceleration in reconnection sites works. Reconnection is expected to be widely spread and such processes can be very common explaining the origin of a substantial part of the cosmic ray population.

Explanation:

Scientific problem: When Voyagers passed the shock surrounding our Solar system they did not detect the change in the spectrum of the cosmic rays that was expected. Most of cosmic rays come from our entire galaxy, but a population of the low energy cosmic rays was always related to the acceleration in the termination shock produced by the interaction of the solar wind and the ambient interstellar medium. This explanation became problematic in view of the discovery by Voyagers.

Solution: The paper identifies magnetic reconnection as the source of anomalous cosmic rays.

Significance: This was the first paper suggesting the new mechanisms of the anomalous cosmic rays. The mechanism is applicable beyond the Solar system and corresponds to the PI’s long claim on the crucial importance of reconnection processes for cosmic ray acceleration (the PI was the first who identified in 2003 the reconnection cites with a very efficient first order Fermi acceleration process, claiming that the reconnection cites as efficient in cosmic ray acceleration as shocks (see more de Gouveia dal Pino & Lazarian 2003, astro-ph/0307054).