Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsh24a..06d&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SH24A-06
Astronomy and Astrophysics
Astrophysics
[2114] Interplanetary Physics / Energetic Particles, [2124] Interplanetary Physics / Heliopause And Solar Wind Termination, [2124] Interplanetary Physics / Heliopause And Solar Wind Termination, [7526] Solar Physics, Astrophysics, And Astronomy / Magnetic Reconnection
Scientific paper
The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyagers 1 and 2 crossed the heliospheric termination shock have called into question the conventional shock source of these energetic particles. We suggest that the sectored heliospheric magnetic field, which results from the flapping of the heliospheric current sheet, piles up as it approaches the heliopause, narrowing the current sheets that separate the sectors and triggering the onset of collisionless magnetic reconnection. Particle-in-cell simulations reveal that most of the magnetic energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The most energetic ions gain energy as they reflect from contracting magnetic islands, a first order Fermi process. The simulations also reveal that the mirror and firehose conditions play an essential role in the reconnection dynamics and particle acceleration. An analytic model is constructed in which the Fermi drive, modulated by the approach to firehose marginality, is balanced by convective loss. The ACR differential energy spectrum takes the form of a power law with a spectral index slightly above 1.5. The model has the potential to explain several key ACR observations, including the similarities in the spectra of different ion species.
Drake James F.
Opher Merav
Schoeffler K. M.
Swisdak Michael
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