Plasmas are systems in which feedback is common. For instance, the plasma particles can drive waves which act back on the particle distributions. Alternatively plasma waves can accelerate particles. Also macroscopic plasma motions can cause or otherwise be associated with macroscopic electric and magnetic fields which cause particle acceleration or the driving of plasma waves, which then act back on the macroscopic plasma motion. Illustrations of some important concepts and the way they interact are given next.
Particle distributions: (i) thermal distributions are Maxwellians, (ii) nonthermal components drift relative to the thermal distribution or have non-Maxwellian features, such as power-law tails or loss cone anisotropies, (iii) can drive and damp plasma waves and radio emissions, (iv) show evidence for particle acceleration or scattering.
Acceleration processes: (i) produce energetic, nonthermal particles, (ii) acceleration by parallel electric fields, (iii) acceleration by or at shock waves, sometimes involving magnetic mirror reflection or plasma drifts, (iv) often lead to wave growth due to anisotropies in the particle distribution function, (v) often revealed by generation of radiation.
Plasma flows and motions: (i) lead to individual particle motions in spatially-varying and fields, (ii) particle drifts can lead to unstable situations, (iii) collective motions make up plasma waves and radiation, (iv) MHD and fluid theory of plasma motions, (v) accleration events.
Plasma Waves: (i) mark the natural resonance frequencies of a plasma, (ii) show the existence of sources of free energy, (iii) Vlasov and fluid theories for instabilities, (iv) can be driven by nonthermal particle distributions, (v) can couple to produce radio emissions, (vi) can scatter or accelerate plasma particles, and (vii) can cause particles to leak from a system.
Radiation: (i) is what reaches us from astrophysical sources, (ii) is generated primarily by nonthermal particle distributions, (iii) can be generated indirectly from plasma waves, and (iv) shows the presence of particle acceleration regions and active phenomena.