  We present a 2D kinematic model to study the acceleration of solar energetic
particles (SEPs) at a shock driven by a coronal mass ejection. The shock is
assumed to be spherical about an origin that is offset from the center of the
Sun. This leads to a spatial and temporal evolution of the angle between the
magnetic field and shock normal direction ($\theta_{Bn}$) as it propagates
through the Parker spiral magnetic field from the lower corona to 1 AU. We find
that the high-energy SEP intensity varies significantly along the shock front
due to the evolution of $\theta_{Bn}$. Generally, the west flank of the shock
preferentially accelerates particles to high energies compared to the east
flank and shock nose. This can be understood in terms of the rate of
acceleration, which is higher at the west flank. Double power-law energy
spectra are reproduced in our model as a consequence of the local acceleration
and transport effects. These results will help better understand the evolution
of SEP acceleration and provide new insights into large SEP events observed by
multi-spacecraft, especially those close to the Sun, such as Parker Solar Probe
and Solar Orbiter.
