The Sun is an efficient particle accelerator. However, the relation between different energetic particle populations is not well-established. Observational studies during the RHESSI era demonstrated the still poorly understood existence of a connection between solar flare signatures of accelerated electrons at the Sun and the corresponding solar energetic particles (SEPs) detected at 1 AU. A fundamental question then arises: can these distinctly observed electron populations come from the same flare-acceleration region or be drawn from the same population of electrons. Observational and theoretical studies alone cannot satisfactorily address this question. Therefore, we aim to combine state-of-the-art multi-instrument observations with kinetic modelling that simultaneously studies the acceleration and transport of flare-accelerated electrons toward and away from the Sun in the varying plasma conditions of the extended solar atmosphere. The model will output and compare with X-ray, radio, and in-situ measurements, allowing us to test whether both electron populations can indeed form within a single, but possibly extended, acceleration region with varying plasma properties. Simultaneous modelling of the escaping and precipitating electron populations will help to constrain the plasma properties of such a region (e.g., its size, temperature, density, turbulence); properties not currently constrained by remote flare observation alone. We will probe various electron transport mechanisms (collisional and non-collisional) in different parts of the solar atmosphere, and combine them with detailed interplanetary transport modelling and multi-spacecraft observations. This will lead to a greater understanding of the important physical processes that modulate the populations during their transport, helping us to study flare particle acceleration from multiple perspectives.

Our full team proposal (minus CVs and contact details) can be found here.