This proposal seeks funds to improve our understanding of solar eruptions and related solar energetic particle (SEP) events (with a focus on SHINE Campaign Events), by means of coupled MHD-SEP numerical simulations. Using the state-of-the-art 3D MagnetoHydroDynamic (MHD) code BATS-R-US, coupled with a new particle code called FLAMPA (Field-Line-Advection Model for Particle Acceleration) recently developed at the University of Michigan, the proposers plan to perform detailed studies of selected SEP events in order to address the following fundamental questions:
(1) How are solar eruptions initiated and how do they evolve? (2) How are solar particles accelerated and transported?
While it is generally accepted that the largest SEP events result from CME-driven shocks in interplanetary space, the relative importance of CME-driven shocks versus flare-associated acceleration of solar particles is an area of active research and debate. Part of this debate arises from our incomplete understanding of shock evolution in the inner corona, and how the conditions encountered there may contribute to SEP variability, especially at high energies relevant for space weather. Only detailed modeling of CMEs throughout the corona can clarify these issues.
The PI will develop three-dimensional numerical models of these events to investigate the dynamics of associated eruptions. In particular, this effort will study how close to the Sun CME-driven shocks form; how the strengths and geometries of these shock waves vary in time; and how the time-dependent changes in shock properties explain the observed signatures of gradual SEP events. The BATS-R-US code's adaptive grid capability will allow the PI to achieve sufficiently high numerical resolution near the Sun to follow CME and shock evolution. The FLAMPA code, on the other hand, will enable the PI to examine the time-dependent transport and diffusive acceleration of solar particles (from protons to the heavy ions of iron) at the CME-driven shocks.
The results of these numerical investigations will be compared with the available data from SoHO, Wind, ACE, and GOES satellites in order to validate and improve the models. These will be the first three-dimensional, coupled MHD-SEP studies focused on understanding the formation and evolution of CME-driven shocks in the inner corona and their role in causing the observed SEP variability.
