Numerical Studies of the Solar Energetic Particle Transport and Acceleration

Abstract

*† ‡ § # Solar energetic particles often get accelerated to energies up to few GeV at interplanetary shock waves driven by Coronal Mass Ejections (CMEs) and are of considerable importance for space weather studies because they can produce radiation hazards for manned or unmanned spacecraft. Particles accelerated at the shock wave can escape upstream and downstream into the interplanetary medium. As the escaped high-energy particles propagate along the interplanetary magnetic field, they are scattered by fluctuations of the turbulent magnetic field. The Monte-Carlo method has been adopted in this work to study propagation and scattering of solar energetic particles. We have demonstrated that high energy particles reach the orbit of the Earth before the bulk flow, which due to its high intensity produces main hazard. The detection of high energy particles may serve as a precursor of its arrival. I. Introduction The solar energetic particle (SEP) events associated with coronal mass ejections (CMEs) are of particular importance for space weather studies. High energy solar protons (~ few GeV) can be accelerated within a short period of time (≤1 hr) after the initiation of solar eruptions, which makes them difficult to predict, and pose a serious concern for the design and operation of both manned and unmanned space missions. Recent theories and related observations 1−7 suggest that these high-energy particles are the result of the first-order Fermi acceleration process 8 at a shock wave driven by a solar eruption, the so-called diffusive shock acceleration (DSA), in the Sun’s proximity (2–15 R : ). These theories, however, have been debated within the community 9−11 because very little is known about the dynamical properties of CME driven shock waves in the inner corona soon after the onset of the eruption and whether or not the level of turbulence at the shock is sufficient for this mechanism to work.