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96-413: Plasma (from Ancient Greek πλάσμα ( plásma )  'moldable substance') is one of four fundamental states of matter (the other three being solid , liquid , and gas ) characterized by the presence of a significant portion of charged particles in any combination of ions or electrons . It is the most abundant form of ordinary matter in the universe , mostly in stars (including

192-468: A ) {\displaystyle q^{2}/(4\pi \epsilon _{0}a)} , and the mean kinetic energy of order k b T {\displaystyle k_{b}T} . When this ratio is small, interactions are weak and the plasma is nearly an ideal gas of charges moving in the mean-field produced by the other charges. However, when Γ > 1 {\displaystyle \Gamma >1} interactions between particles are important and

288-399: A 7-dimensional phase space . When used in combination with a high Hall parameter , a critical value triggers the problematic electrothermal instability which limited these technological developments. Although the underlying equations governing plasmas are relatively simple, plasma behaviour is extraordinarily varied and subtle: the emergence of unexpected behaviour from a simple model is

384-441: A Penning trap and positron plasmas. A dusty plasma contains tiny charged particles of dust (typically found in space). The dust particles acquire high charges and interact with each other. A plasma that contains larger particles is called grain plasma. Under laboratory conditions, dusty plasmas are also called complex plasmas . For plasma to exist, ionization is necessary. The term "plasma density" by itself usually refers to

480-544: A charged plasma particle affects and is affected by the fields created by the other charges. In turn, this governs collective behaviour with many degrees of variation. Plasma is distinct from the other states of matter. In particular, describing a low-density plasma as merely an "ionized gas" is wrong and misleading, even though it is similar to the gas phase in that both assume no definite shape or volume. The following table summarizes some principal differences: Three factors define an ideal plasma: The strength and range of

576-537: A pitch accent . In Modern Greek, all vowels and consonants are short. Many vowels and diphthongs once pronounced distinctly are pronounced as /i/ ( iotacism ). Some of the stops and glides in diphthongs have become fricatives , and the pitch accent has changed to a stress accent . Many of the changes took place in the Koine Greek period. The writing system of Modern Greek, however, does not reflect all pronunciation changes. The examples below represent Attic Greek in

672-407: A balance between electric, magnetic and centrifugal forces: where m is particle mass, q is particle charge, r is radial distance from the trap axis and E r is the radial component of the electric field. This quadratic equation can be solved for the rotational velocity v θ {\displaystyle v_{\theta }} , leading to two solutions, a slow-rotation and

768-510: A density on the order of 10 -10  cm , somewhat less than the Brillouin limit for beryllium in the 4.5 tesla magnetic field of the experiment. Cryogenic temperatures were then required in order to obtain a Γ {\displaystyle \Gamma } value in the strongly coupled regime. The experiments measured the crystal structure by the Bragg-scattering technique, wherein

864-410: A fast-rotation solution. The rate of rotation ω = − v θ / r {\displaystyle \omega =-v_{\theta }/r} for these two solutions can be written as where Ω c = q B / m {\displaystyle \Omega _{c}=qB/m} is the cyclotron frequency . Depending on the radial electric field,

960-523: A few examples given in the following table: Plasmas are by far the most common phase of ordinary matter in the universe, both by mass and by volume. Above the Earth's surface, the ionosphere is a plasma, and the magnetosphere contains plasma. 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 . Furthermore, all

1056-412: A given sign (the sign is assumed to be positive in the figure). In the radial direction, confinement is provided by the v × B Lorentz force due to rotation of the plasma about the trap axis. Plasma rotation causes an inward directed Lorentz force that just balances the outward directed forces caused by the unneutralized plasma as well as the centrifugal force. Mathematically, radial force balance implies

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1152-472: A lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period. They have the same general outline but differ in some of the detail. The only attested dialect from this period is Mycenaean Greek , but its relationship to the historical dialects and

1248-419: A lesser degree. Pamphylian Greek , spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either a fifth major dialect group, or it is Mycenaean Greek overlaid by Doric, with a non-Greek native influence. Regarding the speech of the ancient Macedonians diverse theories have been put forward, but the epigraphic activity and the archaeological discoveries in

1344-457: A means to calculate the electric field from the density: E → = k B T e e ∇ n e n e . {\displaystyle {\vec {E}}={\frac {k_{\text{B}}T_{e}}{e}}{\frac {\nabla n_{e}}{n_{e}}}.} It is possible to produce a plasma that is not quasineutral. An electron beam, for example, has only negative charges. The density of

1440-404: A non-neutral plasma must generally be very low, or it must be very small, otherwise, it will be dissipated by the repulsive electrostatic force . The existence of charged particles causes the plasma to generate, and be affected by, magnetic fields . Plasma with a magnetic field strong enough to influence the motion of the charged particles is said to be magnetized. A common quantitative criterion

1536-412: A plasma. One is based on representing the smoothed distribution function on a grid in velocity and position. The other, known as the particle-in-cell (PIC) technique, includes kinetic information by following the trajectories of a large number of individual particles. Kinetic models are generally more computationally intensive than fluid models. The Vlasov equation may be used to describe the dynamics of

1632-543: A prefix /e-/, called the augment . This was probably originally a separate word, meaning something like "then", added because tenses in PIE had primarily aspectual meaning. The augment is added to the indicative of the aorist, imperfect, and pluperfect, but not to any of the other forms of the aorist (no other forms of the imperfect and pluperfect exist). The two kinds of augment in Greek are syllabic and quantitative. The syllabic augment

1728-519: A result, the system can access novel strongly coupled non-neutral states of matter, including plasma crystals consisting solely of a single charge species. These strongly coupled non-neutral plasmas are parametrized by the coupling parameter Γ, defined as where T {\displaystyle T} is the temperature and a {\displaystyle a} is the Wigner–Seitz radius (or mean inter-particle spacing), given in terms of

1824-535: A rigid body), then Eq. (1) implies that the radial electric field is proportional to radius r . Solving for E r from this equation in terms of ω {\displaystyle \omega } and substituting the result into Poisson's equation yields This equation implies that the maximum possible density occurs at the Brillouin limit, and has the value where c = 1 / μ 0 ϵ 0 {\displaystyle c=1/{\sqrt {\mu _{0}\epsilon _{0}}}}

1920-401: A rotating field error to the plasma. If the error rotates faster than the plasma, it acts to spin up the plasma (similar to how the spinning blade of a blender causes the food to spin), counteracting the effect of field errors that are stationary in the frame of the laboratory. This rotating field error is referred to as a "rotating wall", after the theory idea that one could reverse the effect of

2016-671: A separate historical stage, though its earliest form closely resembles Attic Greek , and its latest form approaches Medieval Greek , and Koine may be classified as Ancient Greek in a wider sense. There were several regional dialects of Ancient Greek; Attic Greek developed into Koine. Ancient Greek was a pluricentric language , divided into many dialects. The main dialect groups are Attic and Ionic , Aeolic , Arcadocypriot , and Doric , many of them with several subdivisions. Some dialects are found in standardized literary forms in literature , while others are attested only in inscriptions. There are also several historical forms. Homeric Greek

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2112-609: A standard subject of study in educational institutions of the Western world since the Renaissance . This article primarily contains information about the Epic and Classical periods of the language, which are the best-attested periods and considered most typical of Ancient Greek. From the Hellenistic period ( c.  300 BC ), Ancient Greek was followed by Koine Greek , which is regarded as

2208-428: A system of charged particles interacting with an electromagnetic field. In magnetized plasmas, a gyrokinetic approach can substantially reduce the computational expense of a fully kinetic simulation. Plasmas are studied by the vast academic field of plasma science or plasma physics , including several sub-disciplines such as space plasma physics . Plasmas can appear in nature in various forms and locations, with

2304-479: A trap asymmetry by simply rotating the entire trap at the plasma rotation frequency. Since this is impractical, one instead rotates the trap electric field rather than the entire trap, by applying suitably phased voltages to a set of electrodes surrounding the plasma. When a non-neutral plasma is cooled to cryogenic temperatures, it does not recombine to a neutral gas as would a neutral plasma, because there are no oppositely charged particles with which to recombine. As

2400-495: A typical feature of a complex system . Such systems lie in some sense on the boundary between ordered and disordered behaviour and cannot typically be described either by simple, smooth, mathematical functions, or by pure randomness. The spontaneous formation of interesting spatial features on a wide range of length scales is one manifestation of plasma complexity. The features are interesting, for example, because they are very sharp, spatially intermittent (the distance between features

2496-510: A vowel or /n s r/ ; final stops were lost, as in γάλα "milk", compared with γάλακτος "of milk" (genitive). Ancient Greek of the classical period also differed in both the inventory and distribution of original PIE phonemes due to numerous sound changes, notably the following: The pronunciation of Ancient Greek was very different from that of Modern Greek . Ancient Greek had long and short vowels ; many diphthongs ; double and single consonants; voiced, voiceless, and aspirated stops ; and

2592-556: Is a literary form of Archaic Greek (derived primarily from Ionic and Aeolic) used in the epic poems , the Iliad and the Odyssey , and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic and other Classical-era dialects. The origins, early form and development of the Hellenic language family are not well understood because of

2688-418: Is added to stems beginning with consonants, and simply prefixes e (stems beginning with r , however, add er ). The quantitative augment is added to stems beginning with vowels, and involves lengthening the vowel: Some verbs augment irregularly; the most common variation is e → ei . The irregularity can be explained diachronically by the loss of s between vowels, or that of the letter w , which affected

2784-406: Is applied across a dielectric gas or fluid (an electrically non-conducting material) as can be seen in the adjacent image, which shows a discharge tube as a simple example ( DC used for simplicity). 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. As

2880-644: Is called 'East Greek'. Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian Greek had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, as exemplified in the poems of the Boeotian poet Pindar who wrote in Doric with a small Aeolic admixture. Thessalian likewise had come under Northwest Greek influence, though to

2976-461: Is called a Penning trap , after the inventor F. M. Penning . The cylindrical version of the trap is also sometimes referred to as a Penning-Malmberg trap, after Prof. John Malmberg. The trap consists of several cylindrically symmetric electrodes and a uniform magnetic field applied along the axis of the trap (Fig 1). Plasmas are confined in the axial direction by biasing the end electrodes so as to create an axial potential well that will trap charges of

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3072-466: Is called the Brillouin limit; it is an equation for the maximum possible radial electric field that allows plasma confinement. This radial electric field can be related to the plasma density n through the Poisson equation , and this equation can be used to obtain a relation between the density and the plasma rotation rate. If we assume that the rotation rate is uniform in radius (i.e. the plasma rotates as

3168-416: Is close to a Maxwellian even in the presence of strong electric or 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. The opposite case

3264-448: Is considered by some linguists to have been closely related to Greek . Among Indo-European branches with living descendants, Greek is often argued to have the closest genetic ties with Armenian (see also Graeco-Armenian ) and Indo-Iranian languages (see Graeco-Aryan ). Ancient Greek differs from Proto-Indo-European (PIE) and other Indo-European languages in certain ways. In phonotactics , ancient Greek words could end only in

3360-501: Is much larger than the features themselves), or have a fractal form. Many of these features were first studied in the laboratory, and have subsequently been recognized throughout the universe. Examples of complexity and complex structures in plasmas include: Striations or string-like structures are seen in many plasmas, like the plasma ball , the aurora , lightning , electric arcs , solar flares , and supernova remnants . They are sometimes associated with larger current densities, and

3456-429: Is necessary to provide the confining radial Lorentz force for the plasma. However, if there is neutral gas in the trap, collisions between the plasma and the gas cause the plasma rotation to slow, leading to radial expansion of the plasma until it comes in contact with the surrounding electrodes and is lost. This loss process can be alleviated by operating the trap in an ultra high vacuum. However, even under such conditions

3552-520: Is no oppositely charged species with which to recombine). If the temperature is sufficiently low (typically on the order of 10 mK), the plasma can become a non-neutral liquid or a crystal . The body-centered-cubic structure of these plasma crystals has been observed by Bragg scattering in experiments on laser-cooled pure beryllium plasmas. Non-neutral plasmas with a single sign of charge can be confined for long periods of time using only static electric and magnetic fields. One such configuration

3648-630: Is not affected by Debye shielding . To completely describe the state of a plasma, all of the particle locations and velocities that describe the electromagnetic field in the plasma region would need to be written down. However, it is generally not practical or necessary to keep track of all the particles in a plasma. Therefore, plasma physicists commonly use less detailed descriptions, of which there are two main types: Fluid models describe plasmas in terms of smoothed quantities, like density and averaged velocity around each position (see Plasma parameters ). One simple fluid model, magnetohydrodynamics , treats

3744-638: Is not well defined and is a matter of interpretation and context. 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. Systematic studies of plasma began with

3840-464: Is only n B = 4.8 × 10  cm . The density predicted by Eq.(2), scaled by the Brillouin density, is shown as a function of rotation rate in Fig. (2). Two rotation rates yield the same density, corresponding to the slow and fast rotation solutions. In experiments on single species plasmas, plasma rotation rates in the tens of kHz range are not uncommon, even in the slow rotation mode. This rapid rotation

3936-491: Is predicted to be a first-order phase transition to a body-centered-cubic crystal for Γ ≃ 175 {\displaystyle \Gamma \simeq 175} . Experiments have observed this crystalline state in a pure beryllium ion plasma that was laser-cooled to the millikelvin temperature range. The mean inter-particle spacing in this pure ion crystal was on the order of 10-20  μm , much larger than in neutral crystalline matter. This spacing corresponds to

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4032-409: Is that a particle on average completes at least one gyration around the magnetic-field line before making a collision, i.e., ν c e / ν c o l l > 1 {\displaystyle \nu _{\mathrm {ce} }/\nu _{\mathrm {coll} }>1} , where ν c e {\displaystyle \nu _{\mathrm {ce} }}

4128-434: Is the z-pinch plasma where the ion temperature may exceed that of electrons. Since plasmas are very good electrical conductors , electric potentials play an important role. 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

4224-426: Is the average ion charge (in units of the elementary charge ). Plasma temperature, commonly measured in kelvin or electronvolts , is a measure of the thermal kinetic energy per particle. High temperatures are usually needed to sustain ionization, which is a defining feature of a plasma. The degree of plasma ionization is determined by the electron temperature relative to the ionization energy (and more weakly by

4320-475: Is the electron gyrofrequency and ν c o l l {\displaystyle \nu _{\mathrm {coll} }} 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

4416-606: Is the ion density and n n {\displaystyle n_{n}} the neutral density (in number of particles per unit volume). In the case of fully ionized matter, α = 1 {\displaystyle \alpha =1} . Because of the quasineutrality of plasma, the electron and ion densities are related by n e = ⟨ Z i ⟩ n i {\displaystyle n_{e}=\langle Z_{i}\rangle n_{i}} , where ⟨ Z i ⟩ {\displaystyle \langle Z_{i}\rangle }

4512-407: Is the speed of light. Thus, the rest energy density of the plasma, n·m·c , is less than or equal to the magnetic energy density B 2 / ( 2 μ 0 ) {\displaystyle B^{2}/(2\mu _{0})} of the magnetic field. This is a fairly stringent requirement on the density. For a magnetic field of 10 tesla, the Brillouin density for electrons

4608-419: Is used in many modern devices and technologies, such as plasma televisions or plasma etching . Depending on temperature and density, a certain number of neutral particles may also be present, in which case plasma is called partially ionized . Neon signs and lightning are examples of partially ionized plasmas. Unlike the phase transitions between the other three states of matter, the transition to plasma

4704-745: The Greek region of Macedonia during the last decades has brought to light documents, among which the first texts written in Macedonian , such as the Pella curse tablet , as Hatzopoulos and other scholars note. Based on the conclusions drawn by several studies and findings such as Pella curse tablet , Emilio Crespo and other scholars suggest that ancient Macedonian was a Northwest Doric dialect , which shares isoglosses with its neighboring Thessalian dialects spoken in northeastern Thessaly . Some have also suggested an Aeolic Greek classification. The Lesbian dialect

4800-563: The Sun ), but also dominating the rarefied intracluster medium and intergalactic medium . Plasma can be artificially generated, for example, by heating a neutral gas or subjecting it to a strong electromagnetic field . The presence of charged particles 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. The response of plasma to electromagnetic fields

4896-501: The present , future , and imperfect are imperfective in aspect; the aorist , present perfect , pluperfect and future perfect are perfective in aspect. Most tenses display all four moods and three voices, although there is no future subjunctive or imperative. Also, there is no imperfect subjunctive, optative or imperative. The infinitives and participles correspond to the finite combinations of tense, aspect, and voice. The indicative of past tenses adds (conceptually, at least)

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4992-530: The voltage increases, the current stresses the material (by electric polarization ) beyond its dielectric limit (termed strength) into a stage of electrical breakdown , marked by an electric spark , where the material transforms from being an insulator into a 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

5088-454: The 1920s, recall that Langmuir first used the term by analogy with the blood plasma . 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." Plasma is called the fourth state of matter after solid , liquid , and gas . It is a state of matter in which an ionized substance becomes highly electrically conductive to

5184-1031: The 5th century BC. Ancient pronunciation cannot be reconstructed with certainty, but Greek from the period is well documented, and there is little disagreement among linguists as to the general nature of the sounds that the letters represent. /oː/ raised to [uː] , probably by the 4th century BC. Greek, like all of the older Indo-European languages , is highly inflected. It is highly archaic in its preservation of Proto-Indo-European forms. In ancient Greek, nouns (including proper nouns) have five cases ( nominative , genitive , dative , accusative , and vocative ), three genders ( masculine , feminine , and neuter ), and three numbers (singular, dual , and plural ). Verbs have four moods ( indicative , imperative , subjunctive , and optative ) and three voices (active, middle, and passive ), as well as three persons (first, second, and third) and various other forms. Verbs are conjugated through seven combinations of tenses and aspect (generally simply called "tenses"):

5280-490: The Archaic period of ancient Greek (see Homeric Greek for more details): Μῆνιν ἄειδε, θεά, Πηληϊάδεω Ἀχιλῆος οὐλομένην, ἣ μυρί' Ἀχαιοῖς ἄλγε' ἔθηκε, πολλὰς δ' ἰφθίμους ψυχὰς Ἄϊδι προΐαψεν ἡρώων, αὐτοὺς δὲ ἑλώρια τεῦχε κύνεσσιν οἰωνοῖσί τε πᾶσι· Διὸς δ' ἐτελείετο βουλή· ἐξ οὗ δὴ τὰ πρῶτα διαστήτην ἐρίσαντε Ἀτρεΐδης τε ἄναξ ἀνδρῶν καὶ δῖος Ἀχιλλεύς. The beginning of Apology by Plato exemplifies Attic Greek from

5376-841: The Classical period of ancient Greek. (The second line is the IPA , the third is transliterated into the Latin alphabet using a modern version of the Erasmian scheme .) Ὅτι [hóti Hóti μὲν men mèn ὑμεῖς, hyːmêːs hūmeîs,   Non-neutral plasmas Non-neutral plasmas are used for research into basic plasma phenomena such as cross-magnetic field transport, nonlinear vortex interactions, and plasma waves and instabilities . They have also been used to create cold neutral antimatter , by carefully mixing and recombining cryogenic pure positron and pure antiproton plasmas. Positron plasmas are also used in atomic physics experiments that study

5472-550: The aorist. Following Homer 's practice, the augment is sometimes not made in poetry , especially epic poetry. The augment sometimes substitutes for reduplication; see below. Almost all forms of the perfect, pluperfect, and future perfect reduplicate the initial syllable of the verb stem. (A few irregular forms of perfect do not reduplicate, whereas a handful of irregular aorists reduplicate.) The three types of reduplication are: Irregular duplication can be understood diachronically. For example, lambanō (root lab ) has

5568-407: The application of electric and/or magnetic fields through a gas. Plasma generated in a laboratory setting and for industrial use can be generally categorized by: Just like the many uses of plasma, there are several means for its generation. However, one principle is common to all of them: there must be energy input to produce and sustain it. For this case, plasma is generated when an electric current

5664-419: The augment when it was word-initial. In verbs with a preposition as a prefix, the augment is placed not at the start of the word, but between the preposition and the original verb. For example, προσ(-)βάλλω (I attack) goes to προσ έ βαλoν in the aorist. However compound verbs consisting of a prefix that is not a preposition retain the augment at the start of the word: αὐτο(-)μολῶ goes to ηὐ τομόλησα in

5760-438: The center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation. One standard formulation for the dialects is: West vs. non-West Greek is the strongest-marked and earliest division, with non-West in subsets of Ionic-Attic (or Attic-Ionic) and Aeolic vs. Arcadocypriot, or Aeolic and Arcado-Cypriot vs. Ionic-Attic. Often non-West

5856-631: The characteristics of plasma were claimed to be difficult to obtain due to the high pressure, the passive effect of plasma on 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 . Ancient Greek language Ancient Greek ( Ἑλληνῐκή , Hellēnikḗ ; [hellɛːnikɛ́ː] ) includes

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5952-393: The density n {\displaystyle n} by the expression 4 π a 3 n / 3 = 1 {\displaystyle 4\pi a^{3}n/3=1} . The coupling parameter can be thought of as the ratio of the mean interaction energy between nearest-neighbor pairs, q 2 / ( 4 π ϵ 0

6048-445: The density). In thermal equilibrium , the relationship is given by the Saha equation . At low temperatures, ions and electrons tend to recombine into bound states—atoms—and the plasma will eventually become a gas. 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

6144-611: The dialect of Sparta ), and Northern Peloponnesus Doric (including Corinthian ). All the groups were represented by colonies beyond Greece proper as well, and these colonies generally developed local characteristics, often under the influence of settlers or neighbors speaking different Greek dialects. After the conquests of Alexander the Great in the late 4th century BC, a new international dialect known as Koine or Common Greek developed, largely based on Attic Greek , but with influence from other dialects. This dialect slowly replaced most of

6240-451: The discharge forms a luminous arc, where the inter-electrode material (usually, a gas) undergoes various stages — saturation, breakdown, glow, transition, and thermal arc. The voltage rises to its maximum in the saturation stage, and thereafter it undergoes fluctuations of the various stages, while the current progressively increases throughout. Electrical resistance along the arc creates heat , which dissociates more gas molecules and ionizes

6336-574: The distant stars , and much of interstellar space or intergalactic space is also filled with plasma, albeit at very low densities. Astrophysical plasmas 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 accreting black holes or in active galaxies like M87's jet that possibly extends out to 5,000 light-years. Most artificial plasmas are generated by

6432-438: The electric force and the good conductivity of plasmas usually ensure that the densities of positive and negative charges in any sizeable region are equal ("quasineutrality"). A plasma with a significant excess of charge density, or, in the extreme case, is composed of a single species, is called a non-neutral plasma . In such a plasma, electric fields play a dominant role. Examples are charged particle beams , an electron cloud in

6528-537: The electron density n e {\displaystyle n_{e}} , that is, the number of charge-contributing electrons per unit volume. The degree of ionization α {\displaystyle \alpha } is defined as fraction of neutral particles that are ionized: α = n i n i + n n , {\displaystyle \alpha ={\frac {n_{i}}{n_{i}+n_{n}}},} where n i {\displaystyle n_{i}}

6624-452: 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", mainly due to a small mean free path (average distance travelled between collisions). Electric arc is a continuous electric discharge between two electrodes, similar to lightning . With ample current density,

6720-489: The filamentation generated plasma is the relatively low ion density due to defocusing effects of the ionized electrons. (See also Filament propagation ) 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 fusion plasma from

6816-663: The forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek ( c.  1400–1200 BC ), Dark Ages ( c.  1200–800 BC ), the Archaic or Epic period ( c.  800–500 BC ), and the Classical period ( c.  500–300 BC ). Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers . It has contributed many words to English vocabulary and has been

6912-556: The historical Dorians . The invasion is known to have displaced population to the later Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with the Dorians. The Greeks of this period believed there were three major divisions of all Greek people – Dorians, Aeolians, and Ionians (including Athenians), each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, and Cypriot, far from

7008-472: The historical circumstances of the times imply that the overall groups already existed in some form. Scholars assume that major Ancient Greek period dialect groups developed not later than 1120 BC, at the time of the Dorian invasions —and that their first appearances as precise alphabetic writing began in the 8th century BC. The invasion would not be "Dorian" unless the invaders had some cultural relationship to

7104-466: The interaction of antimatter with neutral atoms and molecules. Cryogenic pure ion plasmas have been used in studies of strongly coupled plasmas and quantum entanglement . More prosaically, pure electron plasmas are used to produce the microwaves in microwave ovens, via the magnetron instability . Neutral plasmas in contact with a solid surface (that is, most laboratory plasmas) are typically non-neutral in their edge regions. Due to unequal loss rates to

7200-415: The interaction with the magnetic field can form a magnetic rope structure. (See also Plasma pinch ) Filamentation also refers to the self-focusing of a high power laser pulse. At high powers, the nonlinear part of the index of refraction becomes important and causes a higher index of refraction in the center of the laser beam, where the laser is brighter than at the edges, causing a feedback that focuses

7296-409: The laser even more. The tighter focused laser has a higher peak brightness (irradiance) that forms a plasma. The plasma has an index of refraction lower than one, and causes a defocusing of the laser beam. The interplay of the focusing index of refraction, and the defocusing plasma makes the formation of a long filament of plasma that can be micrometers to kilometers in length. One interesting aspect of

7392-499: The older dialects, although the Doric dialect has survived in the Tsakonian language , which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek . By about the 6th century AD, the Koine had slowly metamorphosed into Medieval Greek . Phrygian is an extinct Indo-European language of West and Central Anatolia , which

7488-487: The perfect stem eilēpha (not * lelēpha ) because it was originally slambanō , with perfect seslēpha , becoming eilēpha through compensatory lengthening. Reduplication is also visible in the present tense stems of certain verbs. These stems add a syllable consisting of the root's initial consonant followed by i . A nasal stop appears after the reduplication in some verbs. The earliest extant examples of ancient Greek writing ( c.  1450 BC ) are in

7584-473: The plasma as a single fluid governed by a combination of Maxwell's equations and the Navier–Stokes equations . A more general description is the two-fluid plasma, where the ions and electrons are described separately. Fluid models are often accurate when collisionality is sufficiently high to keep the plasma velocity distribution close to a Maxwell–Boltzmann distribution . Because fluid models usually describe

7680-433: The plasma behaves more like a liquid, or even a crystal if Γ {\displaystyle \Gamma } is sufficiently large. In fact, computer simulations and theory have predicted that for an infinite homogeneous plasma the system exhibits a gradual onset of short-range order consistent with a liquid-like state for Γ ≈ 2 {\displaystyle \Gamma \approx 2} , and there

7776-426: The plasma high conductivity, the electric field associated with a plasma moving with velocity v {\displaystyle \mathbf {v} } in the magnetic field B {\displaystyle \mathbf {B} } is given by the usual Lorentz formula E = − v × B {\displaystyle \mathbf {E} =-\mathbf {v} \times \mathbf {B} } , and

7872-500: The plasma in terms of a single flow at a certain temperature at each spatial location, they can neither capture velocity space structures like beams or double layers , nor resolve wave-particle effects. Kinetic models describe the particle velocity distribution function at each point in the plasma and therefore do not need to assume a Maxwell–Boltzmann distribution . A kinetic description is often necessary for collisionless plasmas. There are two common approaches to kinetic description of

7968-488: 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 ( n e = ⟨ Z ⟩ n i {\displaystyle n_{e}=\langle Z\rangle n_{i}} ), but on

8064-424: The plasma rotation can still be slowed through the interaction of the plasma with "errors" in the external confinement fields. If these fields are not perfectly cylindrically symmetric, the asymmetries can torque on the plasma, reducing the rotation rate. Such field errors are unavoidable in any actual experiment, and limit the plasma confinement time. It is possible to overcome this plasma loss mechanism by applying

8160-413: The point that long-range electric and magnetic fields dominate its behaviour. Plasma is typically an electrically quasineutral medium of unbound positive and negative particles (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 electric currents , and any movement of

8256-452: The reactor walls. However, later it was found that the external magnetic fields in this configuration could induce kink instabilities in the plasma and subsequently lead to an unexpectedly high heat loss to the walls. 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

8352-534: The research of Irving Langmuir and his colleagues in the 1920s. Langmuir also introduced the term "plasma" as a description of ionized gas in 1928: Except near the electrodes, where there are sheaths containing very few electrons, the ionized gas contains ions and electrons in about equal numbers so that the resultant space charge is very small. We shall use the name plasma to describe this region containing balanced charges of ions and electrons. Lewi Tonks and Harold Mott-Smith, both of whom worked with Langmuir in

8448-658: The resulting atoms. Therefore, the electrical energy is given to electrons, which, due to their great mobility and large numbers, are able to disperse it rapidly by elastic collisions to the heavy particles. Plasmas find applications in many fields of research, technology and industry, for example, in industrial and extractive metallurgy , surface treatments such as plasma spraying (coating), etching in microelectronics, metal cutting and welding ; as well as in everyday vehicle exhaust cleanup and fluorescent / luminescent lamps, fuel ignition, and even in supersonic combustion engines for aerospace engineering . A world effort

8544-565: The same sign of charge have exceptional confinement properties compared to neutral plasmas. They can be confined in a thermal equilibrium state using only static electric and magnetic fields, in a Penning trap configuration (see Fig. 1). Confinement times of up to several hours have been achieved. Using the "rotating wall" method , the plasma confinement time can be increased arbitrarily. Such non-neutral plasmas can also access novel states of matter. For instance, they can be cooled to cryogenic temperatures without recombination (since there

8640-747: The scale of the Debye length , there can be charge imbalance. In the special case that double layers are formed, the charge separation can extend some tens of Debye lengths. The magnitude of the potentials and electric fields must be determined by means other than simply finding the net charge density . A common example is to assume that the electrons satisfy the Boltzmann relation : n e ∝ exp ⁡ ( e Φ / k B T e ) . {\displaystyle n_{e}\propto \exp(e\Phi /k_{\text{B}}T_{e}).} Differentiating this relation provides

8736-403: The sense that only a tiny fraction of the gas molecules are ionized. 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 resistive magnetohydrodynamics with low magnetic Reynolds number , a challenging field of plasma physics where calculations require dyadic tensors in

8832-469: The solutions for the rotation rate fall in the range 0 ≤ ω / Ω c ≤ 1 {\displaystyle 0\leq \omega /\Omega _{c}\leq 1} . The slow and fast rotation modes meet when the electric field is such that q E r / m r = Ω c 2 / 4 {\displaystyle qE_{r}/{mr}={\Omega _{c}}^{2}/4} . This

8928-399: The surface for electrons and ions, an electric field (the "ambipolar field" ) builds up, acting to hold back the more mobile species until the loss rates are the same. The electrostatic potential (as measured in electron-volts) required to produce this electric field depends on many variables but is often on the order of the electron temperature. Non-neutral plasmas for which all species have

9024-517: The syllabic script Linear B . Beginning in the 8th century BC, however, the Greek alphabet became standard, albeit with some variation among dialects. Early texts are written in boustrophedon style, but left-to-right became standard during the classic period. Modern editions of ancient Greek texts are usually written with accents and breathing marks , interword spacing , modern punctuation , and sometimes mixed case , but these were all introduced later. The beginning of Homer 's Iliad exemplifies

9120-475: Was Aeolic. For example, fragments of the works of the poet Sappho from the island of Lesbos are in Aeolian. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, or to an island. Doric notably had several intermediate divisions as well, into Island Doric (including Cretan Doric ), Southern Peloponnesus Doric (including Laconian ,

9216-730: Was triggered in the 1960s to study magnetohydrodynamic converters in order to bring MHD power conversion to market with commercial power plants of a new kind, converting the kinetic energy of a high velocity plasma into electricity with no moving parts at a high efficiency . Research was also conducted in the field of supersonic and hypersonic aerodynamics to study plasma interaction with magnetic fields to eventually achieve passive and even active flow control around vehicles or projectiles, in order to soften and mitigate shock waves , lower thermal transfer and reduce drag . Such ionized gases used in "plasma technology" ("technological" or "engineered" plasmas) are usually weakly ionized gases in

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