Plasma (physics)

• 1. The Radiant Matter Hypothesis

  ›

  In 1816, a twenty-four-year-old Michael Faraday delivered lectures titled On Radiant Matter. He proposed that matter existed in forms beyond the known solid, liquid, and gas states. Faraday described this new state as existing far beyond vaporization just as vaporization exists above fluidity. His notes from these early lectures listed reasons for belief in its existence alongside experimental evidence. He observed light within electrical discharges occurring inside air and other gases at varying pressures. This hypothesis remained purely theoretical during his lifetime. Sir William Crookes later presented findings to the British Association for the Advancement of Science on Friday, the 22nd of August 1879. Crookes used the term radiant matter to honor Faraday's earlier speculations while presenting laboratory observations.

  1810

• 2. Quasineutrality And Collective Motion

  ›

  Plasma consists of unbound positive ions and negative electrons moving freely yet generating collective electromagnetic fields. These charged particles create electric currents that affect every other particle within the medium. The overall charge remains roughly zero across large volumes due to quasineutrality. Individual particles experience forces from distant charges rather than simple binary collisions found in neutral gases. Moving plasma generates magnetic fields that influence subsequent motion through Lorentz forces. Electrons often complete gyration around magnetic field lines before colliding with other particles. This magnetized behavior creates anisotropic properties where parallel directions differ from perpendicular ones. High conductivity allows plasmas to behave like fluids governed by Maxwell's equations combined with Navier-Stokes dynamics.

  3725

• 3. Fluid Versus Kinetic Descriptions

  ›

  Physicists use fluid models to describe plasmas as smoothed quantities like density and averaged velocity. Magnetohydrodynamics treats the entire plasma as a single fluid flowing at specific temperatures. These models fail when collision rates drop below thresholds required for Maxwell-Boltzmann distributions. Kinetic models track individual particle velocities without assuming smooth distribution functions. Particle-in-cell techniques follow trajectories of thousands of separate particles simultaneously. Such simulations require significantly more computational power than fluid approaches. Vlasov equations describe systems interacting with electromagnetic fields without relying on collision assumptions. Gyrokinetic methods reduce expense by focusing on electron motion relative to magnetic field lines. Researchers choose between these frameworks based on whether collisionality dominates or if wave-particle effects matter most.

  41619

• 4. Stars And The Solar Wind

  ›

  More than 99 percent of all ordinary matter in the visible universe exists as plasma. Stars function as pure balls of plasma heated by nuclear fusion processes. The solar wind expels plasma from the Sun's surface extending outward to the heliopause. Interplanetary space fills with this expelled material while interstellar regions contain diffuse plasma clouds. Accretion disks surround compact objects like white dwarfs, neutron stars, and black holes. Active galaxies such as M87 produce jets possibly stretching five thousand light-years into space. Lightning discharges thirty kiloamperes at voltages reaching one hundred megavolts near Earth's poles. Auroras form where plasma energy pours back into the atmosphere creating green glowing curtains above the north pole.

  11844

• 5. Electric Breakdown And Ionization

  ›

  Generating artificial plasma requires applying electric current across a dielectric gas until electrical breakdown occurs. Voltage increases stress the material beyond its dielectric strength triggering an electric spark. Electrons bound to atoms detach during collisions creating ions and additional free electrons. This Townsend avalanche process multiplies charged particles millions-fold after twenty successive collision sets. Electric arcs form continuous discharge paths between electrodes resembling natural lightning strikes. Jacob's Ladder devices demonstrate rising plasma columns created by voltage differences in air. Fluorescent lamps utilize glow discharges generated by direct current or radio frequency fields below 100 kilohertz. Capacitively coupled systems operate at frequencies around 13.56 megahertz for microfabrication etching tasks.

  62053

• 6. Industrial Etching And Fusion Research

  ›

  Plasma technology enables surface treatments including spraying coatings onto metal components. Microelectronics manufacturing relies on plasma enhanced chemical vapor deposition processes inside vacuum chambers. Dielectric barrier discharges functionalize synthetic fabrics allowing paints and glues to adhere effectively. Researchers established plasma medicine using low-temperature atmospheric pressure plasmas to inactivate bacterial cells in the mid-1990s. Magnetohydrodynamic converters triggered global research efforts starting in the 1960s to convert kinetic energy into electricity without moving parts. These devices aimed to produce commercial power plants with high efficiency rates. Supersonic combustion engines use plasma ignition systems to improve fuel burning performance. Modern fusion experiments attempt to confine hot plasma using magnetic fields despite kink instabilities causing heat loss to reactor walls.

  54551