Dust observations from Parker Solar Probe: dust ejection from the inner Solar System

Abstract

Context. The FIELDS instrument onboard Parker Solar Probe (PSP) observes dust impacts on the spacecraft. The derived dust flux rates suggest that the particles originate from the vicinities of the Sun and are ejected by radiation pressure. Radiation pressure typically ejects particles of several 100 nm and smaller, which are also affected by the electromagnetic force. Aims. We aim to understand the influence of the electromagnetic force on the dust trajectories and to predict the dust fluxes along the orbit of PSP, within 1 AU and near Earth. Methods. We study the trajectories of dust particles influenced by gravity, radiation pressure, and the electromagnetic force assuming that pitch-angle scattering can be neglected (scatter-free approximation). We estimate the dust fluxes along the second orbit of PSP and in the vicinity of the Earth based on average dust velocities derived from the trajectory calculations and dust production rates derived from a fragmentation model. Results. The calculated cumulative flux of dust particles larger than 100 nm is of the same order (within a factor of ~2) as implied by PSP observations. In this size interval, the dynamics of most particles is dominated by the radiation pressure force. The Lorentz force becomes more important for smaller particles and fluxes can vary with magnetic field conditions. The calculated flux of the 30 to 75 nm particles at the PSP is negligible for most of the second orbit, except for an isolated peak at the perihelion. The 30–75 nm particles that were created inwards from 0.16 AU from the Sun are in trapped orbits if the radiation pressure force is weaker than gravity, which is the case for dust from asteroids and for cometary dust that was altered in space. Conclusions. The inner Solar System is the most likely source of dust smaller than 100 nm that enters Earth’s atmosphere and our results suggest the flux is time-variable.

Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum

“…As further described in Pusack et al (2021), these differences are also suggestive of a Geminids β-stream. We note that grains that are smaller than the detected β-meteoroids and affected by electromagnetic forces have a much larger flux close to the orbital perihelia than at other parts of the orbit (Mann & Czechowski 2021), yet their detection is difficult with PSP /FIELDS due to the low expected impact charge generated by such small mass grains (Szalay et al 2021). Fig.…”

“…From the first three orbits, it was determined that the flux of β-meteoroids varies by approximately 50%, suggesting the inner solar system's collisional environment varies on timescales of 100's of days (Malaspina et al 2020c). Additionally, nanograins with radii below 100 nm were not found to appreciably contribute to the observed impact rates from these first orbits (Mann & Czechowski 2021).…”

First dust measurements with the Solar Orbiter Radio and Plasma Wave instrument

“…Szalay et al (2020) showed that the observations during the second solar encounter could be explained through particles that form as collision fragments near the Sun and then are ejected by the radiation pressure force. Mann & Czechowski (2021) showed that the same fluxes could be explained with a model that combines the collisional production of dust particles and their dynamics influenced by gravity, radiation pressure, and Lorentz force; the latter was found to have only a small effect on the particles that were observed with PSP during the second orbit.…”

“…The mass distribution of fragments is of the form m −0.76 , with the largest fragment mass specified as some (collision-velocity dependent) fraction of the target mass. A brief description of the collision model is given in Mann & Czechowski (2005), while the derivation of dust fluxes is described in Mann & Czechowski (2021). They are obtained from the dust trajectories under the influence of gravity and radiation pressure (since the Lorentz force does not have a strong influence for the considered dust sizes).…”

Dynamics of nanodust in the vicinity of a stellar corona: Effect of plasma corotation

“…The Electromagnetic Fields Investigation (FIELDS) antenna instrument package (Bale et al 2016) during the first PSP orbits measured impact events that are consistent with the trajectories of particles under the effect of gravity and radiation pressure force (Page et al 2020;Szalay et al 2020;Malaspina et al 2020). Comparison to a dust collision and dynamics model suggests that the majority of detected particles are 30 nm and larger (Mann & Czechowski 2021). The trajectory of the PSP is evolving, with the orbit perihelion approaching the Sun.…”