A MAGNETIC RECONNECTION MECHANISM FOR THE GENERATION OF ANOMALOUS COSMIC RAYS

Journal Article · Mon Feb 01 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/709/2/963· OSTI ID:21392295

Drake, J F ^[1]; Opher, M ^[2]; Swisdak, M

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1. Department of Physics and the Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States)
2. Department of Physics and Astronomy, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyager 1 and Voyager 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 is released and most of this energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The energy gain of the most energetic ions results from their reflection from the ends of contracting magnetic islands, a first-order Fermi process. The energy gain of the ions in contracting islands increases their parallel (to the magnetic field B) pressure p{sub ||} until the marginal fire-hose condition is reached, causing magnetic reconnection and associated particle acceleration to shut down. Thus, the feedback of the self-consistent development of the energetic ion pressure on reconnection is a crucial element of any reconnection-based, particle-acceleration model. The model calls into question the strong scattering assumption used to derive the Parker transport equation and therefore the absence of first-order Fermi acceleration in incompressible flows. A simple one-dimensional model for particle energy gain and loss is presented in which the feedback of the energetic particles on the reconnection drive is included. 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 Voyager observations, including the similarities in the spectra of different ion species.

• OSTI ID: 21392295
• Journal Information: Astrophysical Journal, Vol. 709, Issue 2; Other Information: DOI: 10.1088/0004-637X/709/2/963; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
COSMIC RADIATION
ELECTRONS
ENERGY SPECTRA
INCOMPRESSIBLE FLOW
MAGNETIC FIELDS
MAGNETIC ISLANDS
MAGNETIC RECONNECTION
MAGNETOHYDRODYNAMICS
SIMULATION
SOLAR WIND
TAIL IONS
TRANSPORT THEORY
TURBULENCE
VOYAGER SPACE PROBES
CHARGED PARTICLES
ELEMENTARY PARTICLES
FERMIONS
FLUID FLOW
FLUID MECHANICS
HYDRODYNAMICS
IONIZING RADIATIONS
IONS
LEPTONS
MAGNETIC FIELD CONFIGURATIONS
MECHANICS
RADIATIONS
SOLAR ACTIVITY
SPACE VEHICLES
SPECTRA
STELLAR ACTIVITY
STELLAR WINDS
VEHICLES