Interstellar Dust in the Inner Heliosphere and Impact Detection Capabilities with ESA's Solar Orbiter Spacecraft

Abstract

ESA’s Solar Orbiter spacecraft provides a new opportunity to investigate the inner heliosphere close to sun, by taking measurements with state-of-the-art instruments it will help uncover the mysteries of the Sun. Solar Orbiter is planned for a 7 year mission, reaching as close as 0.28 AU to the sun. Using a process called impact ionization, dust fluxes can be measured during the mission. Some dust particles that reside outside our solar system in the local interstellar clouds can enter the solar system from an upstream direction of 258° Heliocentric Ecliptic Longitude. These dust particles are referred to as interstellar dust. This Master Thesis looks at the prospect of using ESA’s Solar Orbiter for interstellar dust detection through dust impact measurements. Models have been created in this thesis to describe the interstellar dust trajectories and impact velocities on the spacecraft. Comparing possible impact velocities during the orbit to measured dust fluxes helps to interpret the observational data. This has been done for interstellar dust and for interplanetary dust particles in unbound orbits around the sun. The trajectories are determined by solar radiation pressure force and solar gravity. This work does not consider Lorentz Forces in any of the calculations, as it can be assumed all calculated particles have a low enough charge to mass ratio to not be heavily affected by magnetic forces. Impact velocities from interstellar dust are found to range from 40 km/s to 80 km/s when Solar Orbiter travels in the upstream direction (80° to 270°), with the more gravitational dominated particles reaching the highest velocities. Dust impact data show that interplanetary dust particles contribute more to the measured dust flux than interstellar dust when Solar Orbiter is closer to the sun, and the interstellar dust upstream direction (258°) could not be measured with the data. The model calculations show that the gravitational focusing region behind the sun (78°) has a high population density of interstellar dust and high impact velocities and future work should be directed to this region.