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Astron. Astrophys. 316, 506-510 (1996)

Coronal diffusion and high solar latitude recurrent energetic particle increases

J.J. Quenby1, A. Witcombe1, B. Drolias4,1, M. Fränz2,3, and E. Keppler3

1 Astrophysics Group, Blackett Laboratory, Imperial College, Prince Consort Rd., London SW7 2BZ, UK
2 Queen Mary and Westfield College, Mile End Rd, London SE, UK
3 Max-Planck-Institut für Aeronomie, Postfach 20, D-37189 Katlenburg-Lindau, Germany
4 Department of Aeronautics, Roderic Hill Building, Imperial College , Prince Consort Road, London SW7 2AZ, UK

Received 16 February 1996 / Accepted 3 June 1996

Abstract. Ulysses observations have demonstrated that energetic particle flux increases are not only found to be associated with the regularly appearing recurrent fast streams seen at mid solar latitudes but also that they persist with the same periodicity of occurrence to at least img1.gif latitude, well into the region where no accompanying plasma speed enhancement is obviously present. We discuss various models for this high latitude phenomenon including acceleration within a lower latitude fast stream with diffusive escape polewards in latitude or the return of flux from a region beyond Ulysses, but conclude that anisotropy data and other evidence on interplanetary diffusion coefficients support solar coronal acceleration at micro-flare sites followed by diffusion in a network of coronal paths characterised by large field magnitude gradients.

Key words: acceleration of particles - Sun - corona - Sun - particle emission - Sun - flares - Sun - magnetic fields

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Last change: December 30, 1996
© European Southern Observatory (ESO) 1996