Two-dimensional, time-dependent model calculations indicate that an interplay between velocity and spatial diffusion may be responsible for the acceleration of implanted heavy ions in the cometary preshock region. Velocity diffusion (second order Fermi acceleration) accelerates the pickup ions to moderate energies thus creating a seed population for the more efficient diffusive-compressive shock acceleration. Solar wind convection limits the time available for diffusive-compressive acceleration, therefore the resulting energy spectrum above 100 keV is a power law with a spectral index of 5 - 6, a value which is in reasonably good agreement with observations.


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    Title :

    Combined first and second order Fermi acceleration at comets


    Contributors:

    Published in:

    Publication date :

    1989-01-01



    Type of media :

    Miscellaneous


    Type of material :

    No indication


    Language :

    English


    Keywords :


    Combined first and second order Fermi acceleration at comets

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    Acceleration Modes in Fermi Accelerator

    Saif, F. / Rehman, I. U. | British Library Online Contents | 2013


    Comets

    Engineering Index Backfile | 1953