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We present numerical modelling of particle acceleration at coronal shockspropagating through a streamer-like magnetic field by solving the Parkertransport equation with spatial diffusion both along and across the magneticfield. We show that the location on the shock where the high-energy particleintensity is the largest, depends on the energy of the particles and on time.The acceleration of particles to more than 100 MeV mainly occurs in theshock-streamer interaction region, due to perpendicular shock geometry and thetrapping effect of closed magnetic fields. A comparison of the particle spectrato that in a radial magnetic field shows that the intensity at 100 MeV (200MeV) is enhanced by more than one order (two orders) of magnitude. Thisindicates that the streamer-like magnetic field can be an important factor inproducing large solar energetic particle events. We also show that the energyspectrum integrated over the simulation domain consists of two different powerlaws. Further analysis suggests that it may be a mixture of two distinctpopulations accelerated in the streamer and open field regions, where theacceleration rate differs substantially. Our calculations also show that theparticle spectra are affected considerably by a number of parameters, such asthe streamer tilt angle, particle spatial diffusion coefficient, and shockcompression ratio. While the low-energy spectra agree well with standarddiffusive shock acceleration theory, the break energy ranges from $\sim$1 MeVto $\sim$90 MeV and the high-energy spectra can extend to $\sim$1 GeV with aslope of $\sim$2-3.

The Acceleration of Energetic Particles at Coronal Shocks and Emergence of a Double Power Law Feature in Particle Energy Spectra