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The observation and interpretation of electric fields have been crucial to the understanding of space physics, particularly on the kinetic scale. The basic principle for electric field measurements can be considered straightforward. However, it has proven difficult to measure electric fields from current state-of-the-art voltage probes without perturbing the space plasma itself. There are numerous documented observations from electric field instruments that have no geophysical explanation for their behavior, implying that they can only be induced by the interaction between probe and plasma. The cause of these anomalies requires a full understanding of the factors that contribute to the measurements of voltage probes. We developed a procedure to isolate the sources of impedance between various components of a physical voltage probe model and a controlled plasma population via the space physics simulation chamber at the Naval Research Laboratory. This paper describes the laboratory setup, procedure, and results from the first round of tests performed on this voltage probe model and discusses improvements to future campaigns. Initial results show that some changes to the model design and the measurement of plasma parameters are required, but interactions with the plasma are observed, and the calibration method used successfully returns impedance values similar to values from direct measurements. 

Abstract Shocks in collisionless astrophysical plasmas redistribute some of the incident flow energy into both thermal and non‐thermal energy. Quantifying the partition of that energy amongst various particle species or their sub‐populations, and electromagnetic energy, represents a fundamental goal of shock physics. It embodies the role of the equation of state for the system. Here we apply a framework to assess all the incident and downstream energy fluxes at a crossing of Earth's bow shock for which the upstream magnetic field was roughly aligned with the shock normal direction. Such quasi‐parallel shocks are known to be non‐steady and to produce significant populations of suprathermal particles. We quantify the evolution of all the important carriers of energy flux through the shock region. We sub‐divide the proton population into thermal, suprathermal, and energetic components in order to investigate the shock's efficiency in energizing the nonthermal particles. While the largest energy fluxes are found in the incident proton ram energy and downstream proton thermal enthalpy fluxes, a significant suprathermal population pervades the regions both up‐ and downstream. We also evaluate the energy fluxes attributable to fluctuations in the fluid and field parameters. 

The current state of the art thermal particle measurements in the solar wind are insufficient to address many long standing, fundamental physical processes. The solar wind is a weakly collisional ionized gas experiencing collective effects due to long-range electromagnetic forces. Unlike a collisionally mediated fluid like Earth’s atmosphere, the solar wind is not in thermodynamic or thermal equilibrium. For that reason, the solar wind exhibits multiple particle populations for each particle species. We can mostly resolve the three major electron populations (e.g., core, halo, strahl, and superhalo) in the solar wind. For the ions, we can sometimes separate the proton core from a secondary proton beam and heavier ion species like alpha-particles. However, as the solar wind becomes cold or hot, our ability to separate these becomes more difficult. Instrumental limitations have prevented us from properly resolving features within each ion population. This destroys our ability to properly examine energy budgets across transient, discontinuous phenomena (e.g., shock waves) and the evolution of the velocity distribution functions. Herein we illustrate both the limitations of current instrumentation and why higher resolutions are necessary to properly address the fundamental kinetic physics of the solar wind. This is accomplished by directly comparing to some current solar wind observations with calculations of velocity moments to illustrate the inaccuracy and incompleteness of poor resolution data.