Collisional Evolution of the Inner Zodiacal Cloud

Abstract

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 is historically difficult to directly measure and has never been observed for discrete meteoroid streams. After six orbits with Parker Solar Probe (PSP), its dust impact rates are consistent with at least three distinct populations: bound zodiacal dust grains on elliptic orbits (α-meteoroids), unbound β-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 (“β-streams”). The β-stream from the Geminids meteoroid stream is a favorable candidate for the third impactor population. β-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 10–20 solar radii and expect this region to also produce the majority of pickup ions due to dust in the inner solar system. A zodiacal erosion rate of at least ∼100 kg s−1 and flux of β-meteoroids at 1 au of (0.4–0.8) × 10−4 m−2 s−1 are found to be consistent with the observed impact rates. The β-meteoroids investigated here are not found to be primarily responsible for the inner source of pickup ions, suggesting nanograins susceptible to electromagnetic forces with radii below ∼50 nm are the inner source of pickup ions. We expect the peak deposited energy flux to PSP due to dust to increase in subsequent orbits, up to 7 times that experienced during its sixth orbit.

First Results From the SCM Search‐Coil Magnetometer on Parker Solar Probe

“…Previous studies (Malaspina et al, 2020;Pusack et al, 2021;Szalay et al, 2020Szalay et al, , 2021 have shown that the dust count rate varies considerably with the distance to the Sun, but also the relative motion and orientation of the spacecraft. This rate is highest during the encounter phase.…”

PSP/WISPR Observations of Dust Density Depletion near the Sun. II. New Insights from within the Depletion Zone

“…In other PSP-based dust studies, Szalay et al (2021) recently showed that the trajectory of PSP around its perihelion is passing through regions of variable dust density. In addition to the orbiting zodiacal dust particles, there are some regions of increased dust density, as for example, in the trails of short-period comets or asteroids (e.g., Stenborg et al 2018b;Battams et al 2020, and references therein), or in circumsolar rings nearby the orbits of Venus (Leinert & Moster 2007;Jones et al 2013Jones et al , 2017Stenborg et al 2021a) or Earth (e.g., Reach et al 1995).…”

Modeling Meteoroid Impacts on the Juno Spacecraft

“…This would also explain the existence of gaps in the first 180 days after 2013 January 1, when on certain days Jorgensen et al (2021) reports 100+ STEs per day (i.e., total of 1000+ impacts per day considering 7% STE detection efficiency), while on subsequent days there are no impacts recorded at all. This kind of behavior does not follow the expected Poisson statistics seen for other meteoroid-related phenomena, such as impacts on other spacecraft (e.g., Page et al 2020;Pusack et al 2021;Szalay et al 2021), meteor detections at Earth (e.g., Pokorný & Brown 2016;Jenniskens et al 2020), or responses of airless bodies to meteoroid impacts (e.g., Burger et al 2014;Szalay & Horányi 2015). For an overview of the observations and modeling of meteoroid-related phenomena, see the recent review work by Janches et al (2021).…”

“…In fact, there are almost no STEs between the G1 and G2 data gaps, where Juno's R hel reaches its minimum below 1 au. From a multitude of in-situ spacecraft data, we know there should be a considerable meteoroid flux of bound grains at and below 1 au (e.g., Gruen et al 1980;Szalay et al 2021), and we would not expect the zodiacal cloud to exhibit increasing density with increasing heliocentric distance. What causes the discord between the observation and the model?…”