Interstellar dust measured in situ by Ulysses: New aspects of the particle size distribution and its modulation by the heliosheath

Vol. 698
9. The Sun and the Heliosphere

Interstellar dust measured in situ by Ulysses: New aspects of the particle size distribution and its modulation by the heliosheath

Pre-solar grains are found in meteorites, even in situ asteroid samples, and are records of the interstellar medium at the origin of the Solar System. This study presents an analysis of a few remarkable secure recoveries of the contemporary interstellar dust in the solar neighborhood, including a few massive particles that can be separated from heliospheric residents. The ULYSSES probe, tasked with surveying the pole of the Sun, exited the ecliptic and attained altitudes of more than 2 au for a decade. The result presented here is for the gold standard detections, distinguished by their distributions in space and momentum. The authors provide a comprehensive survey of the possible effects of propagation through the heliosphere that serves as a tutorial for understanding the basis of the analysis. The derived gas-to-dust mass ratio for the very local interstellar medium is around 500, but constrained to between about 60 and 1000. They conclude with a discussion of how future missions that include directionally sensitive dust detectors will improve and extend this work.