Analysis of dust impacts observed with the Radio Plasma Wave instrument onboard ESA’s Solar Orbiter

Abstract

Dust particles are one of the major constituents of the interplanetary medium in our solar system. They are presumably formed by fragmentation processes of meteoroids and for a certain range of sizes and parameters the dust particles move radially outwards from the Sun. The Radio plasma Wave (RPW) instrument on Solar Orbiter can measure dust particles that impact the spacecraft. By measuring the impacting dust particles we hope to learn about the size and mass distribution of the dust particles formed by the fragmentation processes. For this thesis we investigate the amplitudes of observed dust impact signals from a set of convolutional neural network processed RPW data. The observations extend from June 2020 to June 2023 and during this period, Solar Orbiter reaches as close as 0.29 AU from the Sun. The model assumption is that the mass and the impact velocity of the dust particle is correlated to the measured voltage amplitude. We searched for systematic variations for recorded dust signals along the orbit of Solar Orbiter and the measured voltage amplitude were divided into three categories. The categories was compared for inbound and outbound trajectories as well as perihelion and aphelion paths. Assuming we have a constant impact velocity the slope of the mass distribution was derived. In addition, under the assumption of a constant dust velocity we infer the ratio of small particles along the orbit. Many of the results indicate a mass distribution that increases with the distance from the Sun. Further the results showed that the dust impact flux is higher on an inbound trajectory compared to an outbound trajectory. A possible explanation for this is the influence of the relative velocity in the impact velocity and potential changes of the mass distribution.