Diffusive Shock Acceleration in Structured Solar Wind

Abstract:

Solar energetic particle (SEP) events, especially at high energies are rare and hence may require some special conditions to exist. Sufficiently high level of Alfvenic turbulence is needed for the fast acceleration of particles in shocks driven by coronal mass ejections in solar wind. However, the turbulence level observed in association with SEP events is highly intermittent, which may be essential for the particle emission to upstream of the shock or back to the Sun. Several model cases are considered to illustrate how the pre-existing solar wind structures can affect the acceleration and escape of solar energetic ions.  The model includes both the shock acceleration and the stochastic re-acceleration by the shock-amplified turbulence with account for the turbulence attenuation caused by the particle re-acceleration. Implications for the Solar Orbiter and Solar Probe Plus science are discussed.