Numerical and experimental evidence for a new interpretation of residence times in space

Abstract

Aims. We investigate the energy dependence of Jovian electron residence times, which allows for a deeper understanding of adiabatic energy changes that occur during charged particle transport, as well as of their significance for simulation approaches. Thereby we seek to further validate an improved approach to estimate residence times numerically by investigating the implications on previous analytical approaches and possible effects detectable by spacecraft data. Methods. Utilising a propagation model based on a stochastic differential equation (SDE) solver written in CUDA, residence times for Jovian electrons were calculated over the whole energy range dominated by the Jovian electron source spectrum. We analysed the interdependences both with the magnetic connection between the observer and the source as well as between the distribution of the exit (simulation) times and the resulting residence times. Results. We point out a linear relation between the residence time for different kinetic energies and the longitudinal shift of the 13 month periodicity typically observed for Jovian electrons and discuss the applicability of these findings to data. Furthermore, we utilise our finding that the simulated residence times are approximately linearly related to the energy loss for Jovian and Galactic electrons, and we develop an improved analytical estimation in agreement with the numerical residence time and the longitudinal shift observed by measurements.