A kinetic perspective of electron trapping near a weakly outgassing comet

Abstract: The European Space Agency’s Rosetta spacecraft followed the comet 67P/Churyumov-Gerasimenko from August 2014 to September 2016, providingobservations of the comet ionosphere at varying heliocentric distances. Measurementsfrom the Rosetta mission have shown a multitude of non-thermalelectron distributions in the cometary environment, challenging the previouslyassumed origin and plasma interaction mechanisms near a cometary nucleus.In this thesis, we discuss electron trapping near a weakly outgassing cometfrom a fully kinetic (particle-in-cell) perspective which self consistently describethe ambipolar field. Using electromagnetic fields derived from the simulation,we characterize the trajectories of trapped electrons in the potentialwell surrounding the cometary nucleus and identify the distinguishing featuresin their respective velocity and pitch angle distributions. In accordancewith theoretical findings in space plasma, our analysis allows us to define aclear boundary in velocity phase space between the distributions of trappedand passing electrons.