Modelling the transport of relativistic solar protons along a heliospheric current sheet during historic GLE events

Abstract

There are many difficulties associated with forecasting high-energy solar particle events at Earth. One issue is understanding why some large solar eruptive events trigger ground level enhancement (GLE) events and others do not. In this work we perform 3D test particle simulations of a set of historic GLEs to understand more about what causes these powerful events. Particular focus is given to studying how the heliospheric current sheet (HCS) affects high-energy proton transport through the heliosphere following an event. Analysis of $\ge$M7.0 flares between 1976$-$2020 shows that active regions located closer to the HCS ($<$10${}^{\circ }$) are more likely to be associated with a GLE event. We found that modelled GLE events where the source region was close to the HCS also led to increased heliospheric transport in longitude and higher count rates (when the Earth was located in the drift direction). In a model that does not include perpendicular diffusion associated with turbulence, the HCS is the dominant mechanism affecting heliospheric particle transport for GLE 42 and 69, and varying other parameters (e.g. a narrow, 10${}^{\circ }$, or wider, 60${}^{\circ }$, injection width) causes little change. Overall in our model, the HCS is relevant in 71$\%$ of our analysed GLEs and including it more accurately reproduces observed intensities near Earth. Our simulations enable us to produce model profiles at Earth that can be compared to existing observations by the GOES satellites and neutron monitors, as well as for use in developing future forecasting models.

ApJ accepted

References in corpus (3)

• An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles
• Solar Energetic Particle transport near a Heliospheric Current Sheet
• Oscillation Maps in the Broadband Radio Spectrum of the 1 August 2010 Event

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• Modelling shock-like injections of solar energetic particles with 3D test particle simulations
• Forecasting >300 MeV SEP events: Extending SPARX to high energies