Dictionary Definition
instability
Noun
1 an unstable order [ant: stability]
2 unreliability attributable to being
unstable
3 a state of disequilibrium (as may occur in
cases of inner ear disease) [syn: imbalance, unbalance] [ant: balance]
4 the quality or attribute of being unstable and
irresolute [syn: unstableness] [ant:
stability, stability]
User Contributed Dictionary
English
Noun
 The quality of being unstable
 In the context of "physicscountable": A state that is not in equilibrium, or in which a small change has a large irreversible effect
Synonyms
Extensive Definition
Instability in systems is generally characterized
by some of the outputs
or internal states
growing without bounds.
Not all systems that are not stable are unstable; systems
can also be marginally
stable or exhibit limit cycle
behavior.
In control
theory, a system is unstable if any of the roots
of its characteristic
equation has real part
greater than zero. This is equivalent to any of the eigenvalues of the state
matrix having real part greater than zero.
In structural
engineering, a structure can become unstable when excessive
load is applied. Beyond a certain threshold, structural deflections magnify stresses,
which in turn increases deflections. This can take the form of
buckling or crippling.
The general field of study is called structural
stability.
Fluid instabilities
Fluid instabilities
occur in liquids,
gases and plasmas,
and are often characterized by the shape that form; they are
studied in fluid
dynamics and magnetohydrodynamics.
Fluid instabilities include:
 Ballooning mode instability (some analogy to the Rayleigh–Taylor instability); found in the magnetosphere
 Atmospheric instability
 Bénard instability
 Drift mirror instability
 Kelvin–Helmholtz instability (similar, but different from the diocotron instability in plasmas)
 Rayleigh–Taylor instability
 PlateauRayleigh instability (similar to the Rayleigh–Taylor instability)
 RichtmyerMeshkov instability (similar to the Rayleigh–Taylor instability)
Plasma instabilities
Plasma instabilities can be divided into two general groups (1) hydrodynamic instabilities (2) kinetic instabilities. Plasma instabilities are also categorised into different modes:Mode(azimuthal wave number)NoteDescriptionRadial
modesDescription m=0Sausage instability:displays harmonic
variations of beam radius with distance along the beam axisn=0Axial
hollowing n=1Standard sausaging n=2Axial bunching m=1Sinuous, kink
or hose instability:represents transverse displacements of the beam
crosssection without change in the form or in a beam
characteristics other than the position of its center of mass
m=2Filamentation modes:growth leads towards the breakup of the beam
into separate filaments.Gives an elliptic crosssection m=3Gives a
pyriform (pearshaped) crosssection
Source: Andre Gsponer, "Physics of highintensity
highenergy particle beam propagation in open air and outerspace
plasmas" (2004)
List of plasma instabilities
 Bennett pinch instability (also called the zpinch instability )
 Beam acoustic instability
 Bumpintail instability
 Buneman instability, (same as FarleyBuneman instability?)
 Cherenkov instability,
 Chute instability
 Coalescence instability,
 Collapse instability
 Counterstreaming instability
 Cyclotron instabilities, including:

 Alfven cyclotron instability
 Electron cyclotron instability
 Electrostatic ion cyclotron Instability
 Ion cyclotron instability
 Magnetoacoustic cyclotron instability
 Proton cyclotron instability
 Nonresonant BeamType cyclotron instability
 Relativistic ion cyclotron instability
 Whistler cyclotron instability
 Diocotron instability, (similar to the KelvinHelmholtz fluid instability).
 Disruptive instability (in tokamaks)
 Double emission instability
 Drift wave instability
 Edgelocalised modes http://news.bbc.co.uk/1/hi/sci/tech/3260985.stm
 FarleyBuneman instability
 Fan instability
 Filamentation instability
 Firehose instability (also called Hose instability)
 Flute instability
 Free electron maser instability
 Gyrotron instability
 Helical instability (helix instability)
 Helical kink instability
 Hose instability (also called Firehose instability)
 Interchange instability
 Ion beam instability
 Kink instability
 Lower hybrid (drift) instability (in the Critical ionization velocity mechanism)
 Magnetic drift instability
 Magnetic buoyancy instability (Parker instability)
 Modulation instability
 NonAbelian instability (see also ChromoWeibel Instability)
 ChromoWeibel Instability
 Nonlinear coalescence instability
 Oscillating two stream instability, see two stream instability
 Pair instability
 Parker instability (magnetic buoyancy instability)
 Peratt instability (stacked toroids)
 Pinch instability
 Sausage instability
 Slow Drift Instability
 Tearing mode instability
 Two stream instability
 Weak beam instability
 Weibel instability
 zpinch instability, also called Bennett pinch instability
Notes
External links
instability in German: Instabilität
instability in Spanish: Inestabilidad
instability in French: Instabilité
(homonymie)
instability in Russian: Нестабильность
instability in Slovenian: Nestabilnost
instability in Ukrainian:
Нестійкість
Synonyms, Antonyms and Related Words
ambitendency, ambivalence, caducity, capriciousness, chanciness, change of mind,
changeability,
changeableness,
choppiness, corruptibility, criticalness, danger, dappleness, death, decrepitude, delicacy, desultoriness, deviability, deviation, difference, differentiation,
disorder, divarication, divergence, diversification,
doublemindedness, doubtfulness, dubiety, dubiousness, eccentricity, ephemerality, ephemeralness, erraticism, evanescence, fencesitting,
fencestraddling, fickleness, finitude, fleetingness, flightiness, freakishness, fugacity, hazard, hazardousness, impermanence, impermanency, impulsiveness, incapacity, inconsistency, inconstancy, indecision, indecisiveness, inequality, infirmity, infirmity of
purpose, insecurity,
insipidity, insolidity, insubstantiality,
invalidism, irregularity, irresolution, jerkiness, mercuriality, momentariness, moodiness, mortality, motleyness, mugwumpery, mugwumpism, mutability, nonconformism, nonconformity, nonstandardization,
nonuniformity,
peril, perilousness, perishability, pluralism, precariousness, raggedness, restlessness, ricketiness, risk, riskiness, second thoughts,
senility, shakiness, shiftiness, shiftingness, slipperiness, speculativeness, sword
of Damocles, tergiversation, ticklish
business, ticklishness, totteriness, touchiness, transience, transiency, transientness, transitoriness, treacherousness,
treachery, unauthenticity, unauthoritativeness,
uncertainty,
unconformism,
unconformity,
undecidedness,
undependability,
undeterminedness,
unevenness, unfaithworthiness,
unfirmness, unfixedness, unhealthiness, unorthodoxy, unpredictability,
unreliability,
unsafeness, unsettledness, unsettlement, unsolidity, unsoundness, unstableness, unsteadfastness,
unsteadiness,
unsturdiness,
unsubstantiality,
unsureness, untrustworthiness,
vapidity, variability, variation, variegation, variety, variousness, versatility, volatility, wantonness, wateriness, wavering, waywardness, whimsicality,
wishywashiness