Exploration of kinetic plasma physics through in-situ phase-space measurements in laboratory

The study of plasma dynamics at the kinetic scale (scales smaller than the particle gyroradius) requires detailed measurements of the complete phase space (3D position and 3D velocity) of

the plasma constituents. In space plasmas, this goal is readily accomplished with instruments aboard spacecraft whose dimensions are typically smaller than the Debye length and the electron gyroradius. Recent space missions provide many examples of kinetic scale measurements that have advanced our understanding of the governing physics for those

systems. In the laboratory, where phase space measurements at the electron gyroradius scale are much more challenging, such measurements in low temperature plasmas have validated

theoretical predictions for particle acceleration by Alfvén waves, stochastic ion heating, and particle heating magnetic reconnection. The PHAse Space MApping (PHASMA) experiment employs non-perturbative, optical diagnostics for multi-dimensional ion velocity distribution function, electron velocity distribution function, magnetic field, and turbulence measurements

at the kinetic scale. A primary scientific goal of PHASMA is to explore the processes whereby energy stored in magnetic fields is converted into kinetic energy of the ions and electrons during magnetic reconnection. Over the past few decades, there has been considerable progress in developing theoretical models of magnetic reconnection. The models are distinguishable by their predictions of electron thermal anisotropy and spatial structure of heating throughout the reconnection region. 3D electron phase space measurements in PHASMA during electron-only reconnection have confirmed theoretical predictions of models in which the primary mechanism for electron heating is the parallel electric field that arises during electron-only reconnection. Those measurements, along with measurements of suprathermal electron generation and wave-particle coupling during reconnection, will be described and discussed.