Abstract We present results of a study of the diffusion coefficient for low-energy protons upstream of three interplanetary shocks observed on ISEE-3. The intensity increase as the shock approaches can be fitted by a running exponential, the e-folding time t of which is assumed to be a direct measure of the diffusion coefficient. The energy dependence of t close to the shock (0–60 Re) is derived from the four energy channels covering the range 35–238 keV. The t in the low energy channels (less than 100 keV) increases with distance away from the shock. However t decreases above 100 keV and roughly beyond 100 Re, so that the diffusion coefficient becomes independent of energy. We suggest that the energy-independence of t in a region well upstream of the shock is the result of enhanced parallel scattering through 90° pitch-angles for higher energy (larger gyroradius) particles which are more sensitive to variations in the transverse direction of the magnetic field.


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    Title :

    Diffusion coefficients of low-energy protons upstream of quasi-parallel interplanetary shocks


    Contributors:
    van Nes, P. (author) / Roelof, E.C. (author) / Reinhard, R. (author) / Sanderson, T.R. (author) / Wenzel, K.-P. (author)

    Published in:

    Advances in Space Research ; 4 , 2-3 ; 315-318


    Publication date :

    1984-01-01


    Size :

    4 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English