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* * * * * * * * * * * * * * * * * * Theories of CIR energetic particle acceleration Richardson et al. 1993, after Belcher Davis 1971 Solar wind and magnetic field signatures of CIRs Fisk Lee acceleration model-- particles in CIRs accelerated by compression at forward and reverse shocks at several AU: propagate in to 1 AU adiabatic deceleration in solar wind included yields distribution function spectra and gradients similar to observations above ~100 keV/n injection energy 5 keV required, ie from postulated suprathermal tail of the solar wind composition similar to source material (assumed to be solar wind suprathermal tail) -- (note: no systematic measurements of solar wind comp. available at that time) L. A. Fisk and M. A. Lee, Astrophys. J., 237, 620, 1980 Fisk Lee CIR spectral form-- CIR spectral form: where: v = particle speed; r = radius of observer; rs = shock radius; ??= shock strength; ???diffusion coefficient? V = solar wind speed note: Jones Ellison (1991) model produces a similar but not identical spectral form without transport (r) term Ulysses observations at 5 AU show well formed shocks and associated intensity increases of ions to 10 MeV Desai et al. 1999 Spectral form: flat below ~1 MeV, steepening at higher energies dashed = FL; dotted = JE spectral index does not follow prediction based on shock compression ratio in Fisk Lee model Desai et al. 1999 Fisk Lee model predicts roll-over of spectra at low energies, since the particles can’t make it back into to 1 AU propagating upstream in the solar wind -- this roll-over is not observed Giacalone, Jokpii and Kota model: addressed puzzle of CIR spectral power law down to very low energies particle energization by compression regions associated with CIRs compression region widths of ~0.03 AU can accelerate particles up to 10 MeV spectra similar to observations (Giaclone et al, ApJ, 573, 845-850, 2002) Giacalone et al. CIR spectrum (blue histogram) vs. March 2000 CIR O spectru