# Multi-spacecraft observations and transport simulations of solar energetic particles for the May 17th 2012 event

## TL;DR

This study combines multi-spacecraft observations and 3D simulations to analyze the propagation of solar energetic particles during the May 17, 2012 event, revealing insights into magnetic connectivity and particle transport across the inner heliosphere.

## Contribution

It introduces a comprehensive multi-spacecraft analysis coupled with advanced simulations to accurately model SEP propagation during a major solar event.

## Key findings

- Simulations successfully reproduce observed time profiles and peak intensities.
- Distinct time profile shapes are identified for well-connected versus weakly connected observers.
- Additional low-energy energetic storm particles are observed at specific locations.

## Abstract

The injection, propagation and arrival of solar energetic particles (SEPs) during eruptive solar events is an important and current research topic of heliospheric physics. During the largest solar events, particles may have energies up to a few GeVs and sometimes even trigger ground-level enhancements (GLEs) at Earth. We study the first GLE-event of solar cycle 24, from 17th May 2012, using data from multiple spacecraft (SOHO, GOES, MSL, STEREO-A, STEREO-B and MESSENGER). These spacecraft are located throughout the inner heliosphere, at heliocentric distances between 0.34 and 1.5 astronomical units (au), covering nearly the whole range of heliospheric longitudes. We present and investigate sub-GeV proton time profiles for the event at several energy channels, obtained via different instruments aboard the above spacecraft. We investigate issues due to magnetic connectivity, and present results of three-dimensional SEP propagation simulations. We gather virtual time profiles and perform qualitative and quantitative comparisons with observations, assessing longitudinal injection and transport effects as well as peak intensities. We distinguish different time profile shapes for well-connected and weakly connected observers, and find our onset time analysis to agree with this distinction. At select observers, we identify an additional low-energy component of Energetic Storm Particles (ESPs). Using well-connected observers for normalisation, our simulations are able to accurately recreate both time profile shapes and peak intensities at multiple observer locations. This synergetic approach combining numerical modeling with multi-spacecraft observations is crucial for understanding the propagation of SEPs within the interplanetary magnetic field. Our novel analysis provides valuable proof of the ability to simulate SEP propagation throughout the inner heliosphere, at a wide range of longitudes.