51. Physics of gases
51.10.+y Kinetic and transport theory of gases
51.20.+d Viscosity, diffusion, and thermal conductivity
51.30.+i Thermodynamic properties, equations of state
51.35.+a Mechanical properties; compressibility
51.40.+p Acoustical properties (see also 43.28 Aeroacoustics and atmospheric sound; for ultrasonic relaxation in gases, see 43.35.F in acoustics appendix)
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.) (see also 52.80 Electric discharges)
51.60.+a Magnetic properties
51.70.+f Optical and dielectric properties
* Sorption, see 82.65.M, and 68.45.D
* Gas-surface interactions, see 82.65.P
* Gas sensors and detectors, see 07.07.D
51.90.+r Other topics in the physics of gases (restricted to new topics in section 51)
52. Physics of plasmas and electric discharges (for astrophysical plasmas, see 95.30.Q; for physics of the ionosphere and magnetosphere, see 94.20 and 94.30)
52.20.-j Elementary processes in plasma
52.20.Dq Particle orbits
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.-b Plasma properties (for chemical reactions in plasma, see 82.40.R)
52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.25.Gj Fluctuation phenomena (for plasma turbulence, see 52.35.R)
52.25.Jm Ionization of plasmas
52.25.Kn Thermodynamics of plasmas
52.25.Mq Dielectric properties
52.25.Nr Emission, absorption, and scattering of X and gamma radiation
52.25.Qt Emission, absorption, and scattering of ultraviolet radiation
52.25.Rv Emission, absorption, and scattering of visible and infrared radiation
52.25.Sw Emission, absorption, and scattering of radio-wave and microwave radiation
52.25.Tx Emission, absorption, and scattering of particles
52.25.Ub Strongly-coupled plasmas
52.25.Vy Impurities in plasmas
52.25.Wz Nonneutral plasmas
52.25.Ya Neutrals in plasma
52.25.Zb Dusty plasmas; plasma crystals
52.30.-q Plasma flow; magnetohydrodynamics (see also 47.65--in fluid dynamics; for MHD generators, see 52.75.F)
52.30.Bt MHD equilibria
52.30.Jb Resistive MHD effects
52.35.-g Waves, oscillations, and instabilities in plasma
52.35.Bj Magnetohydrodynamic waves
52.35.Dm Sound waves
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.35.Kt Drift waves
52.35.Lv Other linear waves
52.35.Mw Nonlinear waves and nonlinear wave propagation (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Nx Other nonlinear interactions and phenomena (e.g., Brillouin scattering and Rayleigh scattering)
52.35.Py Plasma macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh–Taylor, etc.)
52.35.Qz Plasma microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Ra Plasma turbulence
52.35.Sb Solitons; BGK modes
52.35.Tc Shock waves
52.40.-w Plasma interactions
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.40.Hf Plasma–wall interactions; boundary layer effects; plasma sheaths
52.40.Mj Particle beam interactions in plasma
52.40.Nk Laser-plasma interactions (e.g., anomalous absorption, backscattering, magnetic field generation, fast particle generation)
52.50.-b Plasma production and heating
52.50.Dg Plasma sources
* Electric discharges, see 52.80
52.50.Gj Plasma heating (beam injection, radio-frequency and microwave, ohmic, ICR, ECR, and current drive heating)
52.50.Jm Plasma production and heating by laser beams
52.50.Lp Plasma production and heating by shock waves and compression
52.55.-s Magnetic confinement and equilibrium
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, etc.
52.55.Ez Z-Pinch, theta pinch, plasma focus and other pinch devices
52.55.Fa Tokamaks
52.55.Hc Stellarators, spheromaks, compact tori, bumpy tori, and other toroidal confinement devices
52.55.Jd Magnetic mirrors
52.55.Lf Astron, cusp, and other magnetic traps
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.)
52.58.-c Nonmagnetic confinement
52.58.Ei Light-ion inertial confinement
52.58.Hm Heavy-ion inertial confinement
52.58.Ns Other inertial confinement (including laser)
52.58.Qv Electrostatic, high frequency, and other nonmagnetic confinement
52.60.+h Relativistic plasma
52.65.-y Plasma simulation
52.65.Cc Particle orbit and trajectory
52.65.Ff Fokker-Planck equation
52.65.Kj Magnetohydrodynamic and fluid equation
52.65.Pp Monte Carlo methods
52.65.Rr Particle-in-cell method
52.65.Tt Gyrofluid and gyrokinetic simulations
52.70.-m Plasma diagnostic techniques and instrumentation
52.70.Ds Electric and magnetic measurements
52.70.Gw Radio-frequency and microwave measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.La X-ray and gamma-ray measurements
52.70.Nc Particle measurements
52.75.-d Plasma devices and applications (see also 28.52 Fusion reactors; for ion sources, see 29.25.L, N; for plasma sources, see 52.50.D)
52.75.Di Accelerators and propulsion
52.75.Fk Magnetohydrodynamic generators and thermionic convertors; plasma diodes (see also 84.60.L, N in direct energy conversion and storage)
52.75.Hn Plasma torches
52.75.Kq Plasma switches (e.g., spark gaps)
52.75.Ms Free-electron devices (for free-electron lasers, see 41.60.C)
52.75.Pv High-voltage diodes (for high-current and high-voltage technology, see 84.70)
52.75.Rx Plasma applications in manufacturing and materials processing (etching, surface cleaning, spraying, arc welding, ion implantation, film deposition, etc.)
52.75.Va Devices for generation of coherent radiation
52.80.-s Electric discharges (see also 51.50 Electrical properties of gases)
52.80.Dy Low-field and Townsend discharges
52.80.Hc Glow; corona
52.80.Mg Arcs; sparks; lightning
52.80.Pi High-frequency discharges
52.80.Qj Explosions; exploding wires
52.80.Sm Magnetoactive discharges (e.g., Penning discharges)
52.80.Tn Other gas discharges
52.80.Vp Discharge in vacuum
52.80.Wq Discharge in liquids (for electric breakdown in liquids, see 77.22.J)
52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
52.90.+z Other topics in physics of plasmas and electric discharges (restricted to new topics in section 52)