Particle Transport and Acceleration in a Chaotic Magnetic Field: Implications for Seed Population to Solar Flare and CME

In large Solar Energetic Particle (SEP) events, ions and electrons are accelerated to GeV/nucleon and keV in energy. These very high energetic particles are likely accelerated at fast coronal shocks. Observations have shown that the seed population (the particles that participate in the shock acceleration process) is not the bulk solar wind, but the suprathermal population. In this work, we propose to investigate a novel pre-acceleration mechanism that may provide the needed seed population for the subsequent shock acceleration in large SEP events. We examine the transport and acceleration of charged particles by chaotic electric and magnetic fields during the pre-eruptive period. It is demonstrated that a realistic chaotic magnetic field can be produced by any asymmetric current configurations -one such configuration is an asymmetric current wire loop system (CWLS). Observational studies have established the existence of current loops and current filaments at the solar surface and simple configurations as CWLSs inevitably exist in solar active regions. This suggests that the magnetic field at an active region is very much chaotic and time variation of these current configurations induces time-varying electric fields. Therefore, charged particles can be naturally accelerated. We outline an approximate model to study the pre-acceleration process of seed particles in a solar active region prior to eruptions by considering the transport and acceleration of charged particles in a time-dependent chaotic magnetic field.