Revolutionizing our Understanding of Particle Energization in Space Plasmas Using On-Board Field-Particle Correlator Instrumentation

A leap forward in our understanding of particle energization in plasmas throughout the heliosphere is essential to answer longstanding questions in heliophysics, including the heating of the solar corona, launching of the solar wind, and acceleration of particles that lead to the glowing of the Earth's aurora. Under the typically low-density and high-temperature conditions of heliospheric plasmas, the energization of particles occurs primarily through the collisionless interaction between the electromagnetic fields and the individual plasma particles. To understand how the plasma heating and particle acceleration impacts the macroscopic evolution of the heliosphere, driving phenomena such as extreme space weather, it is critical to understand these collisionless wave-particle interactions on the characteristic ion and electron kinetic timescales. Such understanding requires high-cadence measurements of both the electromagnetic fields and the three-dimensional particle velocity distributions. Although existing instrument technology enables these measurements, a major challenge to maximize the scientific return from these measurements is the limited amount of data that can be transmitted to the ground due to telemetry constraints. A valuable, but not widely used, approach to overcome this limitation is to compute on-board correlations of the maximum-cadence field and particle measurements to improve the sampling time by several orders of magnitude. Here we review the fundamentals of the innovative field-particle correlation technique, present a formulation of the technique that can be implemented on-board spacecraft, and estimate results that can be achieved with existing instrumental capabilities for particle velocity distribution measurements.