Collisional Evolution of the Inner Zodiacal Cloud: In-Situ observations from PSPs first 6 orbits

The zodiacal cloud is one of the largest structures in the solar system and strongly governed by meteoroid collisions near the Sun. Collisional erosion occurs throughout the zodiacal cloud, yet it has been historically difficult to directly measure and has never been observed for discrete meteoroid streams. After six orbits with Parker Solar Probe (PSP), we find that its dust impact rates are consistent with at least three distinct populations: bound zodiacal dust grains on elliptic orbits (-meteoroids), unbound -meteoroids on hyperbolic orbits, and a third population of impactors that may be either direct observations of discrete meteoroid streams or their collisional by-products (-streams). The -stream from the Geminids meteoroid stream is a favorable candidate for the third impactor population. -streams of varying intensities are expected to be produced by all meteoroid streams, particularly in the inner solar system, and are a universal phenomenon in all exozodiacal disks. We find the majority of collisional erosion of the zodiacal cloud occurs in the range of 1020 solar radii and expect this region to also produce the majority of inner source pickup ions due to dust in the inner solar system. Additionally, the -meteoroids investigated were not found to be primarily responsible for these pickup ions, suggesting nanograins susceptible to electromagnetic forces with radii below 50 nm produce the inner source of pickup ions. We discuss the dust environment in the very inner solar system and PSPs dust observations in this inner region of our heliosphere. We also highlight the various observed populations, provide constraints on their relative densities and fluxes, and discuss the erosion rate of zodiacal material.