Perspectives on Interstellar Dust Inside and Outside of the Heliosphere

TL;DR

This paper examines the unexpected detection of large interstellar dust grains near the Solar System, exploring possible explanations including local concentrations and dynamical processes in the interstellar medium, with implications for ISM structure.

Contribution

It provides an analysis of the apparent discrepancy between observed interstellar dust fluxes and established interstellar medium models, proposing potential mechanisms for the observed phenomena.

Findings

Massive grains detected exceed typical interstellar abundances

Local concentration unlikely without dynamical processes

Variations in influx direction suggest small-scale ISM structure

Abstract

Measurements by dust detectors on interplanetary spacecraft appear to indicate a substantial flux of interstellar particles with masses exceeding 10^{-12}gram. The reported abundance of these massive grains cannot be typical of interstellar gas: it is incompatible with both interstellar elemental abundances and the observed extinction properties of the interstellar dust population. We discuss the likelihood that the Solar System is by chance located near an unusual concentration of massive grains and conclude that this is unlikely, unless dynamical processes in the ISM are responsible for such concentrations. Radiation pressure might conceivably drive large grains into "magnetic valleys". If the influx direction of interstellar gas and dust is varying on a ~10 yr timescale, as suggested by some observations, this would have dramatic implications for the small-scale structure of the interstellar medium.