Determining Threshold Instrumental Resolutions for Resolving the Velocity-Space Signature of Ion Landau Damping

Abstract

Unraveling the physics of the entire turbulent cascade of energy in space and astrophysical plasmas from the injection of energy at large scales to the dissipation of that energy into plasma heat at small scales, represents an overarching, open question in heliophysics and astrophysics. The fast cadence and high phase-space resolution of particle velocity distribution measurements on modern spacecraft missions, such as the recently launched Parker Solar Probe, presents exciting new opportunities for identifying turbulent dissipation mechanisms using in situ measurements of the particle velocity distributions and electromagnetic fields. Here we demonstrate how to use data from kinetic numerical simulations of plasma turbulence to create synthetic spacecraft data; this data set can then be used to determine instrumental requirements to identify specific particle energization mechanisms. Using such synthetic data, downsampled to the velocity phase-space resolution available from the plasma instruments on several past and present missions, we compute the resulting velocity-space signature of ion Landau damping using the recently developed Field-Particle Correlation (FPC) technique. We find that only recent missions have sufficiently fine phase-space resolution to resolve the characteristic resonant features of the ion Landau damping signature. Coupled with numerical determinations of the velocity-space signatures of different proposed particle energization mechanisms, this strategy enables the specification of instrumental capabilities required to achieve science goals on the topic of plasma heating and particle acceleration in turbulent heliospheric plasmas. © 2021. American Geophysical Union. All Rights Reserved.