Plasma (physics): Difference between revisions

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'''Plasma''' ({{etymology|grc|''{{wikt-lang|grc|πλάσμα}}'' ({{grc-transl|πλάσμα}})|moldable substance}}) is one of four fundamental [[state of matter|states of matter]], characterized by the presence of a significant portion of [[charged particle]]s in any combination of [[ion]]s or [[electron]]s.<ref name="πλάσμα">{{Cite book|first1=Henry George |last1=Liddell |first2=Robert |last2=Scott |title=A Greek-English Lexicon |chapter=πλάσμα|chapter-url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dpla%2Fsma|access-date=2023-02-10 February 2023|publisher=Clarendon Press |year=1940}}</ref>) is one of four fundamental [[state of matter|states of matter]] (the other three being [[solid]], [[liquid]], and [[gas]]) characterized by the presence of a significant portion of [[charged particle]]s in any combination of [[ion]]s or [[electron]]s. It is the most abundant form of [[ordinary matter]] in the [[universe]], mostly in [[star]]s (including the [[Sun]]), but also dominating the rarefied [[intracluster medium]] and [[Outer space#Intergalactic space|intergalactic medium]].<ref name="Itptma2013a">{{cite book

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Plasma can be artificially generated, for example, by heating a neutral gas or subjecting it to a strong [[electromagnetic field]].<ref name="BoPA2015">{{cite book

The presence of [[Chargedcharged particle|charged particles]]s makes plasma [[electrically conductive]], with the dynamics of individual particles and macroscopic plasma motion governed by collective electromagnetic fields and very sensitive to externally applied fields.<ref name="Itpd2012b">{{cite book |last1=Morozov |first1=A.I.|date=2012 |title=Introduction to Plasma Dynamics |page=30 |publisher=CRC Press| isbn=978-1-4398-8132-3}}</ref> The response of plasma to electromagnetic fields is used in many modern devices and technologies, such as [[plasma display|plasma televisions]] or [[plasma etching]].<ref name="Itptma2013">{{cite book

Unlike the [[phase transition]]s between the other three states of matter, the transition to plasma is not well defined and is a matter of interpretation and context.<ref name="Itpd2012">{{cite book |last1=Morozov |first1=A.I.|date=2012 |title=Introduction to Plasma Dynamics |page=4−5 |publisher=CRC Press|isbn=978-1-4398-8132-3}}</ref> Whether a given degree of ionization suffices to call a substance '"plasma'" depends on the specific phenomenon being considered.

Plasma was first identified in laboratory by [[Sir William Crookes]]. Crookes presented a [[lecture]] on what he called "radiant matter" to the [[British Association for the Advancement of Science]], in Sheffield, on Friday, 22 August 1879.<ref>{{cite web |url=http://www.worldcatlibraries.org/wcpa/top3mset/5dcb9349d366f8ec.html |title=Find in a Library: On radiant matter a lecture delivered to the British Association for the Advancement of Science, at Sheffield, Friday, August 22, 1879 |access-date=2006-05-24 May 2006 |url-status=live |archive-url=https://web.archive.org/web/20060709162459/http://www.worldcatlibraries.org/wcpa/top3mset/5dcb9349d366f8ec.html |archive-date=9 July 2006 |df=dmy-all }} {{cite web |url=http://www.tfcbooks.com/mall/more/315rm.htm |title=Radiant Matter |access-date=24 May 2006 |url-status=live |archive-url=https://web.archive.org/web/20060613212651/http://tfcbooks.com/mall/more/315rm.htm |archive-date=13 June 2006 |df=dmy-all }}</ref>

[[Lewi Tonks]] and Harold Mott-Smith, both of whom worked with Langmuir in the 1920s, recall that Langmuir first used the term by analogy with the [[blood plasma]].<ref>{{cite journal |first=Lewi |last=Tonks |title=The birth of "plasma" |year=1967 |journal=American Journal of Physics |volume=35 |issue=9 |pages=857–858 |doi=10.1119/1.1974266|bibcode=1967AmJPh..35..857T }}</ref><ref>{{cite book|author=Brown, Sanborn C.|chapter=Chapter 1: A Short History of Gaseous Electronics|editor1=Hirsh, Merle N. |editor2=Oskam, H. J.|title=Gaseous Electronics|volume=1|publisher=Academic Press|date=1978|isbn=978-0-12-349701-7|chapter-url=https://books.google.com/books?id=C1UmeQ_E0_AC&pg=PA1|url-status=live|archive-url=https://web.archive.org/web/20171023230956/https://books.google.co.uk/books?hl=en&lr=&id=C1UmeQ_E0_AC&oi=fnd&pg=PA1&ots=vwabB53YqL&sig=SI8DiBRSQI_yGy_DrspkxNLR0rs#v=onepage&q=blood&f=false|archive-date=23 October 2017|df=dmy-all}}</ref> Mott-Smith recalls, in particular, that the transport of electrons from thermionic filaments reminded Langmuir of "the way blood plasma carries red and white corpuscles and germs."<ref>{{cite journal |first=Harold M.|last=Mott-Smith |journal=Nature |volume=233 |issue=5316 |page=219 |year=1971 |title=History of "plasmas" |bibcode=1971Natur.233..219M |doi=10.1038/233219a0 |pmid=16063290 |doi-access=free }}</ref>

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}}</ref><ref>Yaffa Eliezer, Shalom Eliezer, ''The Fourth State of Matter: An Introduction to the Physics of Plasma'', Publisher: Adam Hilger, 1989, {{ISBN|978-0-85274-164-1}}, 226 pages, page 5</ref><ref>{{cite book|author=Bittencourt, J.A.|title=Fundamentals of Plasma Physics|publisher=Springer|date=2004|isbn=9780387209753|page=1|url=https://books.google.com/books?id=qCA64ys-5bUC&pg=PA1|url-status=live|archive-url=https://web.archive.org/web/20170202072845/https://books.google.com/books?id=qCA64ys-5bUC&pg=PA1|archive-date=2 February 2017|df=dmy-all}}</ref> It is a state of matter in which an [[ionized]] substance becomes highly [[Electrical resistivity and conductivity|electrically conductive]] to the point that long-range [[electromagnetism|electric and magnetic fields]] dominate its behaviour.<ref name="Chen, Francis F. 2016 2–3">{{cite book | title=Introduction to Plasma Physics and controlled fusion | author=Chen, Francis F. | year=1984 | publisher=Springer International Publishing | url=https://books.google.com/books?id=WGbaBwAAQBAJ&q=editions:9PGss7GnX-MC | pages=2–3 | url-status=live | archive-url=https://web.archive.org/web/20180115215631/https://books.google.com/books?id=WGbaBwAAQBAJ&printsec=frontcover&dq=editions:9PGss7GnX-MC&hl=en&sa=X&ved=0ahUKEwimuOfm_pXXAhVrzFQKHTrOCaUQ6AEIKDAA | archive-date=15 January 2018 | df=dmy-all | isbn=9781475755954 }}</ref><ref name="Freidberg, Jeffrey P. 2008 121">{{cite book | title=Plasma Physics and Fusion Energy | author=Freidberg, Jeffrey P. | year=2008 | publisher=Cambridge University Press | url=https://books.google.com/books?id=Vyoe88GEVz4C | page=121 | url-status=live | archive-url=https://web.archive.org/web/20161224204205/https://books.google.com/books?id=Vyoe88GEVz4C | archive-date=24 December 2016 | df=dmy-all | isbn=9781139462150 }}</ref>

Plasma is typically an electrically quasineutral medium of unbound positive and negative [[Particle|particlesparticle]]s (i.e., the overall charge of a plasma is roughly zero). Although these particles are unbound, they are not "free" in the sense of not experiencing forces. Moving charged particles generate [[Electricelectric current|electric currents]]s, and any movement of a [[Charged particle|charged]] plasma particle affects and is affected by the [[Electric field|fields]] created by the other charges. In turn, this governs collective behaviour with many degrees of variation.<ref name="Sturrock">{{cite book |title=Plasma Physics: An Introduction to the Theory of Astrophysical, Geophysical & Laboratory Plasmas |last=Sturrock |first=Peter A. |date=1994 |publisher=Cambridge University Press |isbn=978-0-521-44810-9}}</ref><ref>{{cite book |title=The Framework of Plasma Physics |author=Hazeltine, R.D. |author2=Waelbroeck, F.L. |date=2004 |publisher=Westview Press |isbn=978-0-7382-0047-7}}

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Three factors define an ideal plasma:<ref name="Hazeltine">{{cite book|author=Dendy, R. O.|title=Plasma Dynamics|url=https://books.google.com/books?id=puuQM4Dx0zYC&q=plasma+dynamics+dendy&pg=PR19|publisher=Oxford University Press|date=1990|isbn=978-0-19-852041-2|url-status=live|archive-url=https://web.archive.org/web/20180115215631/https://books.google.com/books?id=puuQM4Dx0zYC&pg=PR19&dq=plasma+dynamics+dendy&hl=en&sa=X&ved=0ahUKEwjlvfbU_JXXAhVJxVQKHVSwC5kQ6AEILTAB|archive-date=15 January 2018|df=dmy-all}}</ref><ref>{{cite book|author=Hastings, Daniel|author2=Garrett, Henry|name-list-style=amp |title=Spacecraft-Environment Interactions|isbn=978-0-521-47128-2|publisher=Cambridge University Press|date=2000}}</ref>

*'''The plasma approximation''': The plasma approximation applies when the [[plasma parameter]] Λ,<ref>{{Cite book|url=https://books.google.com/books?id=WGbaBwAAQBAJ&q=editions:9PGss7GnX-MC|title=Introduction to plasma physics and controlled fusion|author=Chen, Francis F.|date=1984|publisher=Plenum Press|others=Chen, Francis F., 1929-|isbn=978-0306413322|edition=2nd|location=New York|oclc=9852700|url-status=live|archive-url=https://web.archive.org/web/20180115215631/https://books.google.com/books?id=WGbaBwAAQBAJ&printsec=frontcover&dq=editions:9PGss7GnX-MC&hl=en&sa=X&ved=0ahUKEwimuOfm_pXXAhVrzFQKHTrOCaUQ6AEIKDAA|archive-date=15 January 2018|df=dmy-all}}</ref> representing the number of charge carriers within the [[Debye sphere]] is much higher than unity.<ref name="Chen, Francis F. 2016 2–3"/><ref name="Freidberg, Jeffrey P. 2008 121"/> It can be readily shown that this criterion is equivalent to smallness of the ratio of the plasma electrostatic and thermal energy densities. Such plasmas are called weakly coupled.<ref>{{Cite book| publisher = WORLD SCIENTIFIC| isbn = 978-981-02-3305-1|id={{isbnt| 978-981-281-554-5}}| last1 = Fortov| first1 = Vladimir E| last2 = Iakubov| first2 = Igor T| title = The Physics of Non-Ideal Plasma| access-date = 2021-03-19 March 2021| date = November 1999| doi = 10.1142/3634| url = http://www.worldscientific.com/worldscibooks/10.1142/3634}}</ref>

*'''Bulk interactions''': The [[Debye length]] is much smaller than the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, where boundary effects may take place. When this criterion is satisfied, the plasma is quasineutral.<ref>{{Cite web|url=http://www.plasma-universe.com/Quasi-neutrality|title=Quasi-neutrality - The Plasma Universe theory (Wikipedia-like Encyclopedia)|website=www.plasma-universe.com|language=en|access-date=2017-10-25 October 2017|url-status=live|archive-url=https://web.archive.org/web/20171026001653/http://www.plasma-universe.com/Quasi-neutrality|archive-date=26 October 2017|df=dmy-all}}</ref>

*'''Collisionlessness''': The electron plasma frequency (measuring [[plasma oscillation]]s of the electrons) is much larger than the electron–neutral collision frequency. When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics. Such plasmas are called collisionless.<ref>{{Cite journal| doi = 10.1070/PU1997v040n01ABEH000200| issn = 1063-7869| volume = 40| issue = 1| pages = 21–51| last = Klimontovich| first = Yu L.| title = Physics of collisionless plasma| journal = Physics-Uspekhi| access-date = 2021-03-19 March 2021| date = 1997-01-31 January 1997| s2cid = 250739485| url = http://iopscience.iop.org/article/10.1070/PU1997v040n01ABEH000200/meta}}</ref>

[[File:plasma fountain.gif|thumb|upright=1.2|right|Artist's [[artistic rendering|rendition]] of the Earth's [[plasma fountain]], showing oxygen, helium, and hydrogen ions that gush into space from regions near the Earth's poles. The faint yellow area shown above the north pole represents gas lost from Earth into space; the green area is the [[aurora borealis]], where plasma energy pours back into the atmosphere.<ref>{{Cite web|title=Plasma Fountain|url=https://pwg.gsfc.nasa.gov/istp/news/9812/solar1.html|access-date=2023-02-10 February 2023|website=pwg.gsfc.nasa.gov}}</ref>]]

In most cases, the electrons and heavy plasma particles (ions and neutral atoms) separately have a relatively well-defined temperature; that is, their energy [[Distribution function (physics)|distribution function]] is close to a [[Maxwell–Boltzmann distribution|Maxwellian]] even in the presence of strong [[electric field|electric]] or [[magnetic field|magnetic]] fields. However, because of the large difference in mass between electrons and ions, their temperatures may be different, sometimes significantly so. This is especially common in weakly ionized technological plasmas, where the ions are often near the [[ambient temperature]] while electrons reach thousands of kelvin.<ref>{{Cite book |last=Hamrang |first=Abbas |title=Advanced Non-Classical Materials with Complex Behavior: Modeling and Applications, Volume 1 |publisher=CRC Press |year=2014 |pages=10}}</ref> The opposite case is the [[z-pinch]] plasma where the ion temperature may exceed that of electrons.<ref>{{Cite journal| doi = 10.1063/5.0009432| issn = 1070-664X| volume = 27| issue = 6| pages = 060901| last = Maron| first = Yitzhak| title = Experimental determination of the thermal, turbulent, and rotational ion motion and magnetic field profiles in imploding plasmas| journal = Physics of Plasmas| date = 1 June 2020-06-01| bibcode = 2020PhPl...27f0901M| doi-access = free}}</ref>

Typically, lightning discharges 30 kiloamperes at up to 100 megavolts, and emits radio waves, light, X- and even gamma rays.<ref>{{Cite web | author= NASA Administrator |date=7 June 2013-06-07 |title=Flashes in the Sky: Earth's Gamma-Ray Bursts Triggered by Lightning |url=http://www.nasa.gov/vision/universe/solarsystem/rhessi_tgf.html |access-date=2023-02-10 February 2023 |website=NASA |language=en}}</ref> Plasma temperatures can approach 30000 K and electron densities may exceed 10²⁴ m⁻³.]]

Since plasmas are very good [[electrical conductor]]s, electric potentials play an important role.{{clarify|what role?|date=October 2017}} The average potential in the space between charged particles, independent of how it can be measured, is called the "plasma potential", or the "space potential". If an electrode is inserted into a plasma, its potential will generally lie considerably below the plasma potential due to what is termed a [[Debye sheath]]. The good electrical conductivity of plasmas makes their electric fields very small. This results in the important concept of "quasineutrality", which says the density of negative charges is approximately equal to the density of positive charges over large volumes of the plasma (<math>n_e = \langle Z\rangle n_i</math>), but on the scale of the [[Debye length]], there can be charge imbalance. In the special case that ''[[Double layer (plasma)|double layers]]'' are formed, the charge separation can extend some tens of Debye lengths.<ref>{{Cite journal| doi = 10.1007/BF00642580 | issn = 1572-946X| volume = 55| issue = 1| pages = 59–83| last = Block| first = Lars P.| title = A double layer review| journal = Astrophysics and Space Science| accessdate = 2021-07-15 July 2021| date = 1978| s2cid = 122977170| url = https://doi.org/10.1007/BF00642580}}</ref>

The existence of charged particles causes the plasma to generate, and be affected by, [[magnetic field]]s. Plasma with a magnetic field strong enough to influence the motion of the charged particles is said to be magnetized. A common quantitative criterion is that a particle on average completes at least one gyration around the magnetic-field line before making a collision, i.e., <math>\nu_{\mathrm{ce}} / \nu_{\mathrm{coll}} > 1</math>, where <math>\nu_{\mathrm{ce}}</math> is the electron [[gyrofrequency]] and <math>\nu_{\mathrm{coll}}</math> is the electron collision rate. It is often the case that the electrons are magnetized while the ions are not. Magnetized plasmas are ''[[anisotropic]]'', meaning that their properties in the direction parallel to the magnetic field are different from those perpendicular to it. While electric fields in plasmas are usually small due to the plasma high conductivity, the electric field associated with a plasma moving with velocity <math>\mathbf{v}</math> in the magnetic field <math>\mathbf{B}</math> is given by the usual [[Lorentz force|Lorentz formula]] <math>\mathbf{E} = -\mathbf{v}\times\mathbf{B}</math>, and is not affected by [[Debye shielding]].<ref>{{Cite web|first=Richard |last=Fitzpatrick |website=Introduction to Plasma Physics |title=Magnetized Plasmas|url=https://farside.ph.utexas.edu/teaching/plasma/lectures/node10.html|access-date=2023-02-10 February 2023}}</ref>

[[File:Magnetic rope.svg|thumb|The complex self-constricting magnetic field lines and current paths in a field-aligned [[Birkeland current]] that can develop in a plasma.<ref>{{Cite web|title=chapter 15|url=https://history.nasa.gov/SP-345/ch15.htm#250|access-date=2023-02-10 February 2023|website=history.nasa.gov|date=January 1976 |last1=Alfven |first1=H. |last2=Arrhenius |first2=G. }}</ref>]]

Plasmas are studied by the vast [[academic field]] of ''plasma science'' or ''plasma physics'',<ref>{{Cite web|url=https://www.colorado.edu/physics/research/plasma-physics|title=Plasma Physics|date=4 May 2016|website=Physics}}</ref> including several sub-disciplines such as [[space plasma physics]].

Plasmas can appear in nature in various forms and locations, summarisedwith a few examples given in the following table:

*Those found inIn [[plasma displays]], including TV screens.

*Inside [[fluorescent lamp]]s (low energy lighting), [[neon sign]]s<ref>[http://ippex.pppl.gov/fusion/glossary.html IPPEX Glossary of Fusion Terms] {{webarchive|url=https://web.archive.org/web/20080308225731/http://ippex.pppl.gov/fusion/glossary.html |date=8 March 2008 }}. Ippex.pppl.gov. Retrieved on 2011-11-19.</ref>

*[[Star]]s<br />(plasmas heated by [[nuclear fusion]])

*The [[interplanetary medium]]<br />(space between planets)

*The [[interstellar medium]]<br />(space between star systems)

Plasmas are by far the most common [[Phase (matter)|phase of ordinary matter]] in the universe, both by mass and by volume.<ref>{{Cite book|last1=Gurnett|first1=D. A.|url=https://books.google.com/books?id=VcueZlunrbcC&pg=PA2%257CPAGE=2%257CISBN=978-0-521-36483-6%257CPUBLISHER|title=Introduction to Plasma Physics: With Space and Laboratory Applications|last2=Bhattacharjee|first2=A.|date=6 January 2005-01-06|publisher=Cambridge University Press|isbn=978-0-521-36483-6|language=en}}{{cite book|last1=Scherer |first1=K. |last2=Fichtner |first2=H. |last3=Heber |first3=B. |title=Space Weather: The Physics Behind a Slogan|date=2005|url=https://books.google.com/books?id=irHgIUtLi0gC&pg=PA138|page=138|isbn=978-3-540-22907-0|publisher=Springer|location=Berlin}}.</ref>

Above the Earth's surface, the ionosphere is a plasma,<ref>{{cite book |last=Kelley |first=M. C. |title=The Earth's Ionosphere: Plasma Physics and Electrodynamics |date=2009 |publisher=Academic Press |isbn=9780120884254 |edition=2nd}}</ref> and the magnetosphere contains plasma.<ref>{{cite journal|last=Russell|first=C.T.|title=The Magnetopause|journal=Physics of Magnetic Flux Ropes|series=Geophysical Monograph Series|date=1990|volume=58|pages=439–453|doi=10.1029/GM058p0439|bibcode=1990GMS....58..439R|isbn=0-87590-026-7|url=http://www-ssc.igpp.ucla.edu/ssc/tutorial/magnetopause.html|access-date=25 August 2018|archive-url=https://web.archive.org/web/20120503220342/http://www-ssc.igpp.ucla.edu/ssc/tutorial/magnetopause.html|archive-date=3 May 2012|url-status=dead}}</ref> 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 [[Heliopause (astronomy)|heliopause]]. Furthermore, all the distant [[star]]s, and much of [[Interstellar medium|interstellar space]] or [[Outer space#Intergalactic space|intergalactic space]] is also likely filled with plasma, albeit at very low densities. [[Astrophysical plasma]]s are also observed in [[accretion disk]]s around stars or compact objects like [[white dwarf]]s, [[neutron star]]s, or [[black holes]] in close [[binary star]] systems.<ref>{{Cite book|last=Mészáros|first=Péter|url=https://books.google.com/books?id=NXvE_zQX5kAC&dq=%2522Black%2520hole%2522%2520plasma%2520acreting&pg=PA99|title=The High Energy Universe: Ultra-High Energy Events in Astrophysics and Cosmology|date=2010-09-16 September 2010|publisher=Cambridge University Press|isbn=978-1-139-49072-6|language=en}}</ref> Plasma is associated with ejection of material in [[astrophysical jets]], which have been observed with accreting black holes<ref>{{Cite book|last1=Raine|first1=Derek J.|url=https://books.google.com/books?id=O3puAMw5U3UC&pg=PA160|title=Black Holes: An Introduction|last2=Thomas|first2=Edwin George|date=2010|publisher=Imperial College Press|isbn=978-1-84816-382-9|language=en}}</ref> or in active [[galaxy|galaxies]] like [[Messier 87#Jet|M87's jet]] that possibly extends out to 5,000 light-years.<ref>{{Cite web|title=APOD: 2004 December 11 - M87's Energetic Jet|url=https://apod.nasa.gov/apod/ap041211.html|access-date=2023-02-10 February 2023|website=apod.nasa.gov}}</ref>

The [[potential difference]] and subsequent [[electric field]] pull the bound electrons (negative) toward the [[anode]] (positive electrode) while the [[cathode]] (negative electrode) pulls the nucleus.<ref name="Chen">{{cite book |title=Plasma Physics and Controlled Fusion |last=Chen |first=Francis F. |date=1984 |publisher=Plenum Press |isbn=978-0-306-41332-2 |url=https://books.google.com/books?id=WGbaBwAAQBAJ&q=editions:9PGss7GnX-MC |url-status=live |archive-url=https://web.archive.org/web/20180115215631/https://books.google.com/books?id=WGbaBwAAQBAJ&printsec=frontcover&dq=editions:9PGss7GnX-MC&hl=en&sa=X&ved=0ahUKEwimuOfm_pXXAhVrzFQKHTrOCaUQ6AEIKDAA |archive-date=15 January 2018 |df=dmy-all }}</ref> As the [[voltage]] increases, the current stresses the material (by [[electric polarization]]) beyond its [[dielectric strength|dielectric limit]] (termed strength) into a stage of [[electrical breakdown]], marked by an [[electric spark]], where the material transforms from being an [[insulator (electrical)|insulator]] into a [[Electrical conductor|conductor]] (as it becomes increasingly [[ionized]]). The underlying process is the [[Townsend avalanche]], where collisions between electrons and neutral gas atoms create more ions and electrons (as can be seen in the figure on the right). The first impact of an electron on an atom results in one ion and two electrons. Therefore, the number of charged particles increases rapidly (in the millions) only "after about 20 successive sets of collisions",<ref name="Leal-Quiros" /> mainly due to a small mean free path (average distance travelled between collisions).{{Citation needed|date=January 2021}}

====Examples of industrial/commercial plasma====

Because of their sizable temperature and density ranges, plasmasPlasmas find applications in many fields of research, technology and industry., Forfor example, in: industrial and extractive [[metallurgy]],<ref name="Gomez">{{Cite journal | last1 = Gomez | first1 = E. | last2 = Rani | first2 = D. A. | last3 = Cheeseman | first3 = C. R. | last4 = Deegan | first4 = D. | last5 = Wise | first5 = M. | last6 = Boccaccini | first6 = A. R. | doi = 10.1016/j.jhazmat.2008.04.017 | title = Thermal plasma technology for the treatment of wastes: A critical review | journal = Journal of Hazardous Materials | volume = 161 | issue = 2–3 | pages = 614–626 | year = 2009 | pmid = 18499345| bibcode = 2009JHzM..161..614G | s2cid = 206069219 }}</ref><ref name="Szałatkiewicz">{{Cite journal | last1 = Szałatkiewicz | first1 = J. | doi = 10.3390/ma9080683 | title = Metals Recovery from Artificial Ore in Case of Printed Circuit Boards, Using Plasmatron Plasma Reactor | journal = Materials | volume = 9 | issue = 8| pages = 683–696 | year = 2016 | pmid = 28773804| pmc = 5512349| bibcode = 2016Mate....9..683S| doi-access = free }}</ref> surface treatments such as [[plasma spraying]] (coating), [[etching]] in microelectronics,<ref name="NRC">{{cite book |author= National Research Council |date=1991 |title=Plasma Processing of Materials : Scientific Opportunities and Technological Challenges |publisher=National Academies Press |isbn= 978-0-309-04597-1}}</ref> metal cutting<ref name="Nemchinsky">{{Cite journal | last1 = Nemchinsky | first1 = V. A. | last2 = Severance | first2 = W. S. | doi = 10.1088/0022-3727/39/22/R01 | title = What we know and what we do not know about plasma arc cutting | journal = Journal of Physics D: Applied Physics | volume = 39 | issue = 22 | pages = R423 | year = 2006 |bibcode = 2006JPhD...39R.423N | s2cid = 116995929 }}</ref> and [[welding]]; as well as in everyday [[Vehicle emissions control|vehicle exhaust cleanup]] and [[Fluorescent lamp|fluorescent]]/[[Electroluminescence|luminescent]] lamps,<ref name="Hippler">{{cite book |editor=Hippler, R. |editor2=Kersten, H. |editor3=Schmidt, M. |editor4=Schoenbach, K.M. |date=2008 |title=Low Temperature Plasmas: Fundamentals, Technologies, and Techniques |chapter=Plasma Sources |publisher=Wiley-VCH |edition=2nd |isbn=978-3-527-40673-9}}</ref> fuel ignition, whileand even playing a part in [[Scramjet|supersonic combustion engines]] for [[aerospace engineering]].<ref name="Peretich">{{cite journal |author=Peretich, M.A. |author2=O'Brien, W.F. |author3=Schetz, J.A. |date=2007 |title=Plasma torch power control for scramjet application |publisher=Virginia Space Grant Consortium |url=http://www.vsgc.odu.edu/src/SRC07/SRC07papers/Mark%20Peretich%20_%20PaperFinal%20Report.pdf |access-date=12 April 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100629193719/http://www.vsgc.odu.edu/src/SRC07/SRC07papers/Mark%20Peretich%20_%20PaperFinal%20Report.pdf |archive-date=29 June 2010 |df=dmy-all }}</ref>

*''[[Glow discharge]] plasmas'': non-thermal plasmas generated by the application of DC or low frequency RF (<100&nbsp;kHz) electric field to the gap between two metal electrodes. Probably the most common plasma; this is the type of plasma generated within [[fluorescent light]] tubes.<ref>{{cite web |url=http://www-spof.gsfc.nasa.gov/Education/wfluor.html |title=The Fluorescent Lamp: A plasma you can use |author=Stern, David P. |access-date=2010-05-19 May 2010 |url-status=live |archive-url=https://web.archive.org/web/20100530165958/http://www-spof.gsfc.nasa.gov/Education/wfluor.html |archive-date=30 May 2010 |df=dmy-all }}</ref>

*''[[Wave heated plasma]]'': similar to CCP and ICP in that it is typically RF (or microwave). Examples include [[helicon discharge]] and [[electron cyclotron resonance]] (ECR).<ref>{{cite book|title=Plasma Chemistry|date=2008|publisher=Cambridge University Press|page=229|url=https://books.google.com/books?id=ZzmtGEHCC9MC&pg=PA229|isbn=9781139471732|url-status=live|archive-url=https://web.archive.org/web/20170202060021/https://books.google.com/books?id=ZzmtGEHCC9MC&pg=PA229|archive-date=2 February 2017|df=dmy-all}}</ref>

*''[[Dielectric barrier discharge]] (DBD):'' this is a non-thermal discharge generated by the application of high voltages across small gaps wherein a non-conducting coating prevents the transition of the plasma discharge into an arc. It is often mislabeled '"Corona'" discharge in industry and has similar application to corona discharges. A common usage of this discharge is in a [[plasma actuator]] for vehicle drag reduction.<ref>{{Cite journal | last1 = Roy | first1 = S. | last2 = Zhao | first2 = P. | last3 = Dasgupta | first3 = A. | last4 = Soni | first4 = J. | title = Dielectric barrier discharge actuator for vehicle drag reduction at highway speeds| doi = 10.1063/1.4942979 | journal = AIP Advances | volume = 6 | issue = 2 | pages = 025322 | year = 2016 | bibcode = 2016AIPA....6b5322R | doi-access = free }}</ref> It is also widely used in the web treatment of fabrics.<ref>{{Cite journal | last1 = Leroux | first1 = F. | last2 = Perwuelz | first2 = A. | last3 = Campagne | first3 = C. | last4 = Behary | first4 = N. | s2cid = 137392051 | title = Atmospheric air-plasma treatments of polyester textile structures | doi = 10.1163/156856106777657788 | journal = Journal of Adhesion Science and Technology | volume = 20 | issue = 9 | pages = 939–957 | year = 2006 }}</ref> The application of the discharge to synthetic fabrics and plastics functionalizes the surface and allows for paints, glues and similar materials to adhere.<ref>{{Cite journal

Such ionized gases used in "plasma technology" ("technological" or "engineered" plasmas) are usually ''weakly ionized gases'' in the sense that only a tiny fraction of the gas molecules are ionized.<ref>{{Cite book|title=Plasma scatteringScattering of electromagnetic radiationElectromagnetic Radiation: theoryTheory and measurementMeasurement Techniques techniques|date=2011|publisher=Academic Press/Elsevier |othersurl=https://books.google.com/books?id=1NS5Fxam1lkC&pg=PA273 |first1=J. |last1=Sheffield |first2=D. |last2=Froula, Dustin|first3=S. H. |last3=Glenzer |first4=N. C. Jr. |last4=Luhmann |isbn=978-0080952031|edition=1st ed., 2nd|location=Burlington, MA|pages=273|oclc=690642377}}</ref> These kinds of weakly ionized gases are also nonthermal "cold" plasmas. In the presence of magnetics fields, the study of such magnetized nonthermal weakly ionized gases involves [[Magnetohydrodynamics#Ideal and resistive MHD|resistive magnetohydrodynamics]] with low [[magnetic Reynolds number]], a challenging field of plasma physics where calculations require [[dyadic tensor]]s in a [[n-dimensional space|7-dimensional]] [[phase space]]. When used in combination with a high [[Hall effect|Hall parameter]], a critical value triggers the problematic [[electrothermal instability]] which limited these technological developments.{{Citation needed|date=January 2021}}

Striations or string-like structures,<ref>{{cite journal|author=Dickel, J. R.|bibcode=1990BAAS...22..832D |title=The Filaments in Supernova Remnants: Sheets, Strings, Ribbons, or?|date=1990|journal=Bulletin of the American Astronomical Society|volume= 22|page=832}}</ref> also known as [[Birkeland current]]s, are seen in many plasmas, like the [[plasma globe|plasma ball]], the [[Aurora (astronomy)|aurora]],<ref>{{Cite journal | last1 = Grydeland | first1 = T. | doi = 10.1029/2002GL016362 | title = Interferometric observations of filamentary structures associated with plasma instability in the auroral ionosphere | journal = Geophysical Research Letters | volume = 30 | issue = 6 | pages = 1338 | year = 2003 | bibcode=2003GeoRL..30.1338G| doi-access = free }}</ref> [[lightning]],<ref>{{Cite journal | last1 = Moss | first1 = G. D. | last2 = Pasko | first2 = V. P. | last3 = Liu | first3 = N. | last4 = Veronis | first4 = G. | title = Monte Carlo model for analysis of thermal runaway electrons in streamer tips in transient luminous events and streamer zones of lightning leaders | doi = 10.1029/2005JA011350 | journal = Journal of Geophysical Research | volume = 111 | issue = A2 | pages = A02307 | year = 2006 | bibcode=2006JGRA..111.2307M| doi-access = free }}</ref> [[electric arc]]s, [[solar flares]],<ref>{{cite journal|author=Doherty, Lowell R.|doi=10.1086/148107|title=Filamentary Structure in Solar Prominences|date=1965|journal=The Astrophysical Journal|volume=141|page=251|last2=Menzel|first2=Donald H.|bibcode=1965ApJ...141..251D}}</ref> and [[supernova remnant]]s.<ref>{{cite web |url=http://seds.lpl.arizona.edu/messier/more/m001_hst.html |title=Hubble views the Crab Nebula M1: The Crab Nebula Filaments |access-date=2017-01-26 January 2017 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20091005084515/http://seds.lpl.arizona.edu/messier/more/m001_hst.html |archive-date=5 October 2009 |df=dmy-all }}. The University of Arizona</ref> They are sometimes associated with larger current densities, and the interaction with the magnetic field can form a [[magnetic rope]] structure.<ref>{{Cite journal | last1 = Zhang | first1 = Y. A. | last2 = Song | first2 = M. T. | last3 = Ji | first3 = H. S. | doi = 10.1016/S0275-1062(02)00095-4 | title = A rope-shaped solar filament and a IIIb flare | journal = Chinese Astronomy and Astrophysics | volume = 26 | issue = 4 | pages = 442–450 | year = 2002 |bibcode = 2002ChA&A..26..442Z }}</ref> (See also [[Plasma pinch]])

Impermeable plasma is a type of thermal plasma which acts like an impermeable solid with respect to gas or cold plasma and can be physically pushed. Interaction of cold gas and thermal plasma was briefly studied by a group led by [[Hannes Alfvén]] in 1960s and 1970s for its possible applications in insulation of [[Nuclear fusion|fusion]] plasma from the reactor walls.<ref>{{cite journal |last1=Alfvén |first1=H. |last2=Smårs |first2=E.|s2cid=26797662 |title= Gas-Insulation of a Hot Plasma |journal=Nature |volume=188 |date=1960 |pages=801–802 |doi=10.1038/188801a0|bibcode = 1960Natur.188..801A |issue=4753 }}</ref> However, later it was found that the external [[magnetic fields]] in this configuration could induce [[Kink instability|kink instabilities]] in the plasma and subsequently lead to an unexpectedly high heat loss to the walls.<ref>{{cite journal |last1=Braams |first1=C.M. |title= Stability of Plasma Confined by a Cold-Gas Blanket |journal=Physical Review Letters |volume=17 |issue=9 |date=1966 |pages=470–471 |doi=10.1103/PhysRevLett.17.470|bibcode = 1966PhRvL..17..470B }}</ref>

In 2013, a group of materials scientists reported that they have successfully generated stable impermeable plasma with no [[magnetic confinement]] using only an ultrahigh-pressure blanket of cold gas. While spectroscopic data on the characteristics of plasma were claimed to be difficult to obtain due to the high pressure, the passive effect of plasma on [[Chemical synthesis|synthesis]] of different [[nanostructures]] clearly suggested the effective confinement. They also showed that upon maintaining the impermeability for a few tens of seconds, screening of [[ions]] at the plasma-gas interface could give rise to a strong secondary mode of heating (known as viscous heating) leading to different kinetics of reactions and formation of complex [[nanomaterials]].<ref>{{cite journal |last1=Yaghoubi |first1=A. |last2=Mélinon |first2=P.|title= Tunable synthesis and in situ growth of silicon-carbon mesostructures using impermeable plasma |journal=Scientific Reports |volume=3 |pages=1083 |date=2013 |doi=10.1038/srep01083|bibcode = 2013NatSR...3E1083Y |pmid=23330064 |pmc=3547321}}</ref>

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