Редовна сбирка на Семинара на Института по Астрономия ще се проведе на 2 юли, 2026 г. (четвъртък), от 14:00 часа в библиотеката на Института.
Артьом Епифанов, редовен докторант на ИА с НАО, ще представи отчет за работата си за тригодишен период на тема:
“High-energy charged particle in the heliosphere and associated emissions. Global Modeling of SEP Propagation During Impulsive Events with the EPREM Model “
Абстракт: Most of my work has been related to the Energetic Particle Radiation Environment Model (EPREM), used for modeling SEPs and particle transport in the inner heliosphere. I have rewritten the original model from C to C++ and introduced the following technical features: async output, memory-mappable output format, instrumented runtime profiling and execution tracing, regression testing, run restarts, SIMD alternatives, as well as other minor improvements. On the side of modeling capabilities, the following was added: relaxation phase, mappable inner boundary, flare model, and some other minor adjustments. A package for run preparation, output resampling and visualization has been developed as well.
I will report current status of the scientific research done. We will cover a study of the global SEP propagation from impulsive events in the 30 RSun – 1 AU domain. We study evolution of the 1-100 MeV proton flux pitch-angle distribution (PAD) and the observed anisotropies at 1 AU, and how it depends on: 1) longitudinal flare-observer offset; 2) PAD prescribed at the inner boundary. The study demonstrates the spatially anisotropic nature of transport of SEPs in the inner heliosphere, shed light on the connection between the source and the observed anisotropy, and highlight the impact of the isotropization on the formation of sunward flux.
The other, more recent study is also going to be presented. This study is focused on Fe/O enhancements during impulsive events that can arise due to transport effects. We take the impulsive event that occurred on 20 May 2024 as our case, and simulate impulsive injection of multiple species with equal source distribution to isolate the effects of transport on the observed Fe/O ratios. We find that rigidity-dependent transport has the most effect on cross-field diffusion, which can give rise to up to 15% ratio enhancement at the edges of the impulse cone. A more extreme version of the effect for Fe/H is presented, leading to peak 3-4x ratio enhancement. We conclude that this contribution, while non-negligible, is not sufficient to explain much higher observed ratio enhancements. Additional effects are discussed.
