The effect of the Meandering Interplanetary Magnetic Field and source spectrum on the time-intensity profile of Ground-level Enhancement (GLE) events.

Abstract:

Ground-level Enhancements (GLEs) are a class of Solar Energetic Particle (SEP) events with sufficient intensity to penetrate Earth’s atmosphere, producing secondary neutrons that are detected by neutron monitors. GLE events are typically produced by protons with an energy is of the order of a GeV. In this study, we investigate the transport of the GeV solar energetic particles in the Interplanetary Magnetic Field (IMF). The SEPs are released near the Sun and the time-intensity profile at one AU is obtained using a fully relativistic 3D test particle simulation which solve the equations of motion for a large number of test particles. The model also includes pitch-angle scattering. We use two models for the IMF: The nominal Parker-spiral magnetic field and the Meandering IMF introduced in Giacalone 2004. Both IMF models include the Heliospheric Current Sheet. The SEPs are scattered using two mean free paths, 0.1 and 0.5 AU. The intensity profile is recorded in the observer’s location, whose position relative to the HCS is varied. We determine how the meandering IMF and also variations in the source spectrum, its intensity, shape, and duration can affect the time-intensity profile of GLE events.