Plasma (Part-III)- The Attributes of the 4th State of Matter

Image for representative purpose only.

How does Plasma differs from gases? How does Plasma appears in nature in various forms?

Now we continue with the third part of our blog on plasma. Those who have missed our second blog can read it from Here. It will help to connect with this third part of the blog discussing details about the difference between plasma and gases and the different forms of plasma that appear in nature.  Let us know about all these minute details of plasma while reading this blog.

Comparison of Plasma and Gas Phase

i) Electrical Conductivity

• Gas at very low: Air is an excellent insulator until it breaks down into plasma at electric field strengths above 30 KV/cm.

• Plasma at very high: For many purposes, the conductivity of a plasma may be treated as infinite.

ii) Independently Acting Species

• One for Gas: All gas particles behave in a similar way, influenced by gravity and by collisions with one another.

• Two or Three for Plasma:  Electrons, ions, protons and neutrons can be distinguished by the sign and value of their charge so that they behave independently in many circumstances, with different bulk velocities and temperatures, allowing phenomena such as new types of waves and instabilities.

iii) Velocity Distribution: 

• Gases are Maxwellian: Collisions usually lead to a Maxwellian velocity distribution of all gas particles, with very few relatively fast particles.

• Plasma are Non-Maxwellian: Collisional interactions are often weak in hot plasma and external forcing can drive the plasma far from local equilibrium and lead to a significant population of unusually fast particles. 

iv) Interactions

• Gases have binary interactions: Two-particle collisions are the rule, three-body collisions extremely rare.

• Plasma have collective interactions: Waves, or organized motion of plasma, are very important because the particles can interact at long ranges through the electric and magnetic forces.

Role of Plasma in Astronomy and Astrophysics

Plasma are by far the most common phase of ordinary matter in the universe, both by mass and by volume. Within our Solar System, interplanetary space is filled with the plasma expelled via the solar wind, extending from the Sun's surface out to the helio-pause. Furthermore, all the distant stars, and much of interstellar space or intergalactic space is also likely filled with plasma, albeit at very low densities. Astrophysical plasma are also observed in Accretion disks around stars or compact objects like white dwarfs, neutron stars, or black holes in close binary star systems.  Plasma is associated with ejection of material in astrophysical jets, which have been observed with accretion black holes or in active galaxies like M87's jet that possibly extends out to 5,000 light-years.

How does Plasma appear in Nature?

Plasma appear in nature in various forms and those are mainly:

i) Artificially Produced

Artificially produced plasma displays, including TV screens. Sometimes Inside fluorescent lamps (low energy lighting), neon signs. They appear in rocket exhaust and ion thrusters. The area in front of a spacecraft's heat shield during re-entry into the atmosphere. Inside a corona discharge ozone generator, fusion energy research, the electric arc in an arc lamp, an arc welder or plasma torch, plasma ball (sometimes called a plasma sphere or plasma globe).Arcs produced by Tesla coils. Plasma used in semiconductor device fabrication including reactive-ion etching, sputtering, surface cleaning and plasma-enhanced chemical vapour deposition. Laser-produced plasma (LPP), found when high power lasers interact with materials. Inductively coupled plasmas (ICP), formed typically in argon gas for optical emission spectroscopy or mass spectrometry. Magnetically induced plasma (MIP), typically produced using microwaves as a resonant coupling method. Static electric sparks, capacitive coupled plasma (CCP), Dielectric Barrier Discharges (DBD) and so on.

ii) Terrestrial Plasma

During the time of lightning terrestrial plasma are found. The magnetosphere contains plasma in the Earth's surrounding space environment. In Earth’s  ionosphere terrestrial plasma is found in the plasma-sphere, the polar aurora, the polar wind, the plasma fountain, upper-atmospheric lightning (e.g. Blue jets, Blue starters, Gigantic jets, ELVES),Sprites and St. Elmo's fire are examples of terrestrial plasma.

iii) Space and Astrophysical Plasma:

In universe plasma are found in stars (plasma heated by nuclear fusion),the solar wind, the interplanetary medium (space between planets) the interstellar medium(space between star systems),the Intergalactic medium (space between galaxies),the Io-Jupiter flux tube, Accretion discs, Interstellar nebulae and so on.

Continued in the next blog...