Ballooning instability

The ballooning instability (a.k.a. ballooning mode instability) is a type of internal pressure-driven plasma instability usually seen in tokamak fusion power reactors{{Cite journal |last1=Dobrott |first1=D. |last2=Nelson |first2=D. B. |last3=Greene |first3=J. M. |last4=Glasser |first4=A. H.|author4-link=Alan Herbert Glasser |last5=Chance |first5=M. S. |last6=Frieman |first6=E. A. |date=1977-10-10 |title=Theory of Ballooning Modes in Tokamaks with Finite Shear |journal=Physical Review Letters |volume=39 |issue=15 |pages=943–946 |doi=10.2172/5115796 |osti=5115796}} or in space plasmas.{{Cite journal|last1=Hameiri|first1=E.|last2=Laurence|first2=P.|last3=Mond|first3=M.|date=1991-02-01|title=The ballooning instability in space plasmas|journal=Journal of Geophysical Research: Space Physics|language=en|volume=96|issue=A2|pages=1513–1526|doi=10.1029/90ja02100|issn=0148-0227|bibcode=1991JGR....96.1513H}} It is important in fusion research as it determines a set of criteria for the maximum achievable plasma beta.{{Cite book|title=Ideal magnetohydrodynamics|last=P.|first=Freidberg, Jeffrey|date=1987|publisher=Plenum Press|isbn=0306425122|location=New York|oclc=15428479}} The name refers to the shape and action of the instability, which acts like the elongations formed in a long balloon when it is squeezed. In literature, the structure of these elongations are commonly referred to as 'fingers'.{{Cite journal|last1=Kleva|first1=Robert G.|last2=Guzdar|first2=Parvez N.|date=2001|title=Fast disruptions by ballooning mode ridges and fingers in high temperature, low resistivity toroidal plasmas|journal=Physics of Plasmas|language=en|volume=8|issue=1|pages=103–109|doi=10.1063/1.1331098|issn=1070-664X|bibcode=2001PhPl....8..103K}}{{Cite journal|last1=Cowley|first1=Steven C.|last2=Wilson|first2=Howard|last3=Hurricane|first3=Omar|last4=Fong|first4=Bryan|date=2003|title=Explosive instabilities: from solar flares to edge localized modes in tokamaks|journal=Plasma Physics and Controlled Fusion|language=en|volume=45|issue=12A|pages=A31|doi=10.1088/0741-3335/45/12A/003|issn=0741-3335|bibcode=2003PPCF...45A..31C|s2cid=250824453 }}{{Cite journal|last1=Panov|first1=E. V.|last2=Sergeev|first2=V. A.|last3=Pritchett|first3=P. L.|last4=Coroniti|first4=F. V.|last5=Nakamura|first5=R.|last6=Baumjohann|first6=W.|last7=Angelopoulos|first7=V.|last8=Auster|first8=H. U.|last9=McFadden|first9=J. P.|date=2012|title=Observations of kinetic ballooning/interchange instability signatures in the magnetotail|journal=Geophysical Research Letters|language=en|volume=39|issue=8|pages=n/a|doi=10.1029/2012gl051668|issn=0094-8276|bibcode=2012GeoRL..39.8110P|doi-access=free}}

The narrow fingers of plasma produced by the instability are capable of accelerating and pushing aside the surrounding magnetic field in order to cause a sudden, explosive release of energy. Thus, the instability is also known as the explosive instability.{{Cite journal|last=Hamasaki|first=Seishi|date=1971|title=Self-Consistent Calculation of an Explosive Instability|journal=Physics of Fluids|language=en|volume=14|issue=7|pages=1441–1451|doi=10.1063/1.1693626|issn=0031-9171|bibcode=1971PhFl...14.1441H}}{{Cite journal|last1=Jones|first1=Michael E.|last2=Fukai|first2=J.|date=1979|title=Evolution of the explosive instability in a simulated beam plasma|journal=Physics of Fluids|language=en|volume=22|issue=1|pages=132|doi=10.1063/1.862440|issn=0031-9171|bibcode=1979PhFl...22..132J}}{{Cite journal|last1=Cowley|first1=S. C.|last2=Cowley|first2=B.|last3=Henneberg|first3=S. A.|last4=Wilson|first4=H. R.|date=2015-08-08|title=Explosive instability and erupting flux tubes in a magnetized plasma|journal= Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=471|issue=2180|pages=20140913|doi=10.1098/rspa.2014.0913|issn=1364-5021|pmc=4550006|pmid=26339193|bibcode=2015RSPSA.47140913C|arxiv=1411.7797}}