Magnetic Reconnection: Concepts and Applications

549 Pages·2016·22.58 MB·English

by  Walter Gonzalez

Astrophysics and Space Science Library 427
Walter Gonzalez
Eugene Parker
Editors
Magnetic
Reconnection
Concepts and Applications
Magnetic Reconnection
Astrophysics and Space Science Library
EDITORIAL BOARD
Chairman
W.B.BURTON,NationalRadioAstronomyObservatory,Charlottesville,
Virginia,U.S.A.([email protected]);UniversityofLeiden,TheNetherlands
([email protected])
F.BERTOLA,UniversityofPadua,Italy
C.J.CESARSKY,CommissionforAtomicEnergy,Saclay,France
P.EHRENFREUND,LeidenUniversity,TheNetherlands
O.ENGVOLD,UniversityofOslo,Norway
A.HECK,StrasbourgAstronomicalObservatory,France
E.P.J.VANDENHEUVEL,UniversityofAmsterdam,TheNetherlands
V.M.KASPI,McGillUniversity,Montreal,Canada
J.M.E.KUIJPERS,UniversityofNijmegen,TheNetherlands
H.VANDERLAAN,UniversityofUtrecht,TheNetherlands
P.G.MURDIN,InstituteofAstronomy,Cambridge,UK
B.V.SOMOV,AstronomicalInstitute,MoscowStateUniversity,Russia
R.A.SUNYAEV,SpaceResearchInstitute,Moscow,Russia
Moreinformationaboutthisseriesathttp://www.springer.com/series/5664
Walter Gonzalez • Eugene Parker
Editors
Magnetic Reconnection
Concepts and Applications
123
Editors
WalterGonzalez EugeneParker
INPE UniversityofChicago
SaQoJosédosCampos,Brazil CHICAGO
Illinois,USA
ISSN0067-0057 ISSN2214-7985 (electronic)
AstrophysicsandSpaceScienceLibrary
ISBN978-3-319-26430-1 ISBN978-3-319-26432-5 (eBook)
DOI10.1007/978-3-319-26432-5
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Cover illustration: See Fig. 4.3 in Chapter 4 “Energy Conversion and Inventory of a Prototypical
MagneticReconnectionLayer”byMasaakiYamadaetal.inthisbook.
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Preface
MotivatedbythepresentationsanddiscussionscarriedoutattheMagneticRecon-
nection Workshop, held at the National Institute for Space Research (INPE) of
Brazil in March 2014, some of the scientists who attended it thought that it was
timely to prepare a new book on magnetic reconnection since previous books on
thistopichavebeenpublishedalreadyeightyearsbeforeormore.Thus,thisbook
dealswithareviewoffundamentalconceptsonmagneticreconnectionthatarestill
openforresearchandwithapplicationsofthisimportantcosmicplasmaprocessto
regionsgoingfromtheSun’satmosphereandtheEarth’smagnetospheretodomains
involvingheliosphericmagnetospheres,stellaratmospheres,turbulentastrophysical
plasmas,radiationdominatedastrophysicalsystems,andevenquantumsystemsin
whichannihilationofquantummagneticfluxesseemstotakeplace.
This book updates and extends the scope of previous books on magnetic
reconnection, especially of those edited by Priest and Forbes (2000) and by Birn
and Priest (2007), to which the readers are referred for reviews on fundamental
aspectsofMHDreconnectionandofcollisionlessreconnection.
Most of the chaptersof thisbookhave beenpreparedhavinggraduatestudents
andpostdocsasthemainreadersinmind,thusprovidingillustrationsandintroduc-
torydiscussionsforthe addressedtopics.However,we believethatallresearchers
in the field of magnetic reconnection will also profit from the reviews presented
in this book since several of the authors have made an effort to incorporate new
researchmaterialintheirreviews.Concerningtheunitsusedinthisbook,because
the chapters were written by different authors with some of them preferring the
MKSsystemandsometheCGSsystem,wehavenotmadetheefforttopresentall
chapterswithonlyoneoftheseunits,also becauseweassume thatthereadersare
alreadyfamiliartofindthissamesituationwhenreadingpapersinwhichtheauthors
prefertouseonesystemortheother.
InChap.1,severalofthebookauthorspresentopinionsabouttwofundamental
questions on magnetic reconnection that still remain unsettled. They refer to the
meaningofthegenerallyusedexpression“magneticfieldlinescutandreconnect”
aswellastothelocationandnatureofa“diffusion”regionofreconnectionandto
its role in defining the reconnection rate, as compared to that associated with the
v
vi Preface
global reconnecting system and the boundary conditions. Although one can read
about illuminating considerations in the discussions presented in this chapter on
suchfundamentalissues,onecanalsoseethatnoconsensusaboutthemispresently
available, thus indicating that the subject of magnetic reconnection remains open
forfurthertheoretical,computational,andobservationalstudies.
Althoughthetopicofcollisionlessreconnectionhasbeenreviewedextensivelyin
recentyears(Yamadaetal.2010;MozerandPritchett2012;Karimabadietal.2013;
Treumann and Baumjohann 2013; Hesse et al. 2014), J. Scudder, H. Karimabadi,
and B. Daughtonpresentin Chap.2 of this booka complementaryreviewdealing
mostly with the electron physics of reconnection and more particularly with the
roleofelectrondemagnetizationincollisionlessreconnection.Fromthisstudythe
authorspresenta setofphenomenologicalparametersthatareintendedtobeused
as proxies to locate the electron diffusion region of reconnection, both in 2D and
3D.
The MHD approach to study reconnection still provides important results
especiallywhenonedealswithglobalaspects.Thus,E.PriestpresentsinChap.3a
review aboutthe different3D-MHD structuresof reconnection,where the electric
currenttendstoconcentrateleadingtoreconnection-relatednullpoints,separators,
and quasi-separators. The review also discusses the role of magnetic helicity and
of other topologicalinvariants,together with the conditionsfor flux and field line
conservationandforreconnectionitself.
In Chap.4, M. Yamada, J. Yoo, and S. Zenitani present a review on energy
conversionandpartitioningforaprototypicalmagneticreconnectionlayer,incorpo-
ratingrecentresultsfromlaboratoryexperiments,spaceobservations,andnumerical
simulations. They conclude that about half of the incident magnetic energy is
convertedintoparticleenergy,ofwhich2/3isultimatelytransferredtoionsand1/3
toelectrons.Theyalsodiscusstheseresultsinthecontextofasystematicvariability
oftheboundaryconditions.
Theimportantproblemofrapidreconnectionandassociatedchangesinfieldline
topology, which has been discussed in several recent publications, is reviewed in
Chap.5by E.N.ParkerandF. Rappazzo.Thissituationariseswhere themagnetic
stresses drive the plasma and field toward increasing field gradients, so that the
current density becomes large without bound, with the plasma dynamics and the
kineticsofthethincurrentsheetcontrollingtherateofthereconnectingfields.The
authors consider where and how the local rapid reconnection phenomenon arises
intheoveralltopologyofthesurroundingmagneticfieldandexemplifyitwiththe
commonbipolarmagneticfieldsarchingabovethesolarphotosphere.Studyingthe
final equilibrium of such a common interlaced field line topology, they conclude
thatthincurrentsheetsformasintrinsicsitesforrapidreconnection.
Magnetopausereconnectionhasbeenoneofthemoststudiedtopicsofmagnetic
reconnectionsincetheinitialworkbyDungey(1961).InChap.6,P.A.Cassakand
S.A. Fuselier present an updatedreview on this topic to give fresh answers to the
fundamentalquestionsofwherereconnectionhappensatthemagnetopauseandhow
efficient it is as a function of the solar wind driving parameters. The chapter is a
pedagogicaltreatmentofmagnetopausereconnection,althoughtheauthorsalsotry
Preface vii
toincorporateresultsofrecentstudiesincludingasymmetries,thediamagneticdrift,
andflowshear.Forthisaim,resultsfromtheoretical,observational,andnumerical
simulationsareused.
In Chap.7, A. Petrukovich, A. Artemyev, and R. Nakamura review the topic
of magnetotail reconnection, which also has a long history of theoretical, obser-
vational, and modeling efforts. The authors discuss the initiation mechanisms
for near-Earth tail reconnection concluding that it still represents one of the
major unsolved problems in space physics. They review progress in this research
topic during the last decade, especially highlighting variants of overcoming the
famous tearing stability problem and discussing with recent multipointspacecraft
observations detailed structures of pre-onset and reconnection zones down to the
ionLarmorscale.Thelatterisarguedtosupporttheimportanceofaself-consistent
formationofanunstablestatethroughinternalmagnetotailreconfiguration.
G.Lapenta,R.Wang,andE.CazzolagiveinChap.8areviewonreconnection
separatricesasstudiedinrecentyearsforbothclassicalregionsofmagnetospheric
reconnection, dayside and tail. The review primarily focuses on numerical simu-
lations but is supplemented with spacecraft observations. The natural importance
of the separatrices lies in the fact that they connect the central region of recon-
nection with the larger-scale external region that also incorporates the boundary
conditions. The authors summarize the average properties of particles and fields
in the separatrix regions, also dealing with the various types of instabilities and
accelerationprocessesthattendtooccurthere.Theyarguethatasignificantpartof
energyconversiontakesplaceintheseparatrixregionsduringreconnection.
Since reconnection is expected to take place also at other planetary magne-
tospheres, Chap.9 is devoted to reviewing some reconnection properties for the
magnetospheres of Jupiter and Saturn and comparing them with those for the
Earth’s magnetosphere. Thus, in this chapter, R. Walker and X. Jia present a
reviewespeciallydealingwithplasmatransportassociatedwithreconnectioninthe
magnetospheresoftheseplanets.Sinceobservationsattheouterplanetsaresparse,
theauthorsuse numericalsimulationsto giveanoverallview ofplasma transport.
TheauthorsclaimthatsolarwinddynamicpressurecontrolsreconnectionatSaturn,
whilebothdynamicpressureandtheIMFareimportantatJupiter.Theyalsopresent
evidenceabouttheimportanceofKelvin-Helmholtzwavesduringtransportforthe
magnetosphereofSaturn.
WhenstudyingreconnectionattheSunandatotherstellarenvironments,recent
resultsshowanimportantfractalreconnectionscenariothatseemstoexplainseveral
apparently unrelated observations. Thus in Chap.10, K. Shibata and S. Takasao
presentareviewonthistopicusingtheoryandobservations.Theauthorsassociate
afractalcurrentsheetstructureasasourceforbothsmall-scalereconnectionatthe
Sun,leadingtonano-flares,andtolarge-scaleones,leadingtolong-durationflaresor
giantarcades.Theymentionthatoftensuchreconnectioneventsarecloselyrelated
withmultipleplasmoidejectionsfromafractalcurrentsheet.Theyclaimthatbursty
radio and hard X-ray emissions from flares also suggest fractal reconnection and
associated particle acceleration. The authors also discuss about recent findings of
manysuperflaresonsolar-typestars, whichseemtoextendtheapplicabilityofthe
viii Preface
fractalreconnectionmodelofsolarflarestoamuchwiderparameterspaceinvolving
stellarflares.
Thetopicofturbulentreconnectionhasreceivedespecialattentionduringrecent
yearswithapplicationsmainlyinastrophysicalsystems.InChap.11,A.Lazarian,
G.Kowal,M.Tamamoto,E.M.DeGouveaDalPino,andJ.Cho,presentareview
onthistopicusingtheoreticalstudiesandnumericalsimulations.Theauthorsclaim
that magnetic reconnection occurs frequently due to the common and ubiquitous
presence of turbulence in cosmic plasmas. They even associate the efficiency
and rate of reconnection to the level of turbulence present in the plasma during
reconnection.Thetheorypresentedinthisreviewisalsoextendedtotherelativistic
domain.
Sincereconnectioninastrophysicalsystemsfrequentlyinvolvesradiationsthere
has been increasing efforts trying to incorporate radiation in the reconnection
dynamicsandenergeticsinsuchscenarios.Thus,inChap.12,D.Uzdenskyreviews
this subject, presenting an overview of recent theoretical progress and key high-
energyastrophysicalapplicationsofradiativereconnectiontopulsarwindnebulae,
pulsarmagnetospheres,blackholeaccretion-diskcoronae,andhotaccretionflows
in X-ray binaries and active galactic nuclei, with important consequences for the
studyofrelativisticjets,magnetospheresofmagnetars,andgamma-raybursts.
Finally,inChap.13,W.D.Gonzalezreviewstheveryrecenttopicofannihilation
of quantum magnetic fluxes (QMFs) which, although observed to occur until
now only in laboratory superconducting systems, is argued to also occur at the
superconducting outer core of neutron stars with a probable role in the observed
variabledynamicsof some neutronstars. The authorpresentsa synthesisof some
fundamentalaspects associated with QMFs, including the Aharonov-Bohmeffect
forthephasechangeofelectronspassingintheneighborhoodoflocalizedmagnetic
flux tubes, the Ginzburg-Landau phenomenological theory explaining the origin
ofQMFs,some laboratoryobservationsofQMFsinsuperconductingsystems,the
Treumannetal. (2012)quantummechanicalstudyofthe interactionofoppositely
directedQMFs,a quantumfieldtheoryapproachforthestudyoftheenergeticsof
the annihilationof QMFs and of the emitted radiation,and a discussion aboutthe
possiblescenarioofQMF-annihilationatthesuperconductingcoresofsomeneutron
stars.
The editors would like to thank the efforts done by the contributingauthors to
thisbookandexpectthatitscontentbeusefulespeciallytonewresearchersinthe
fieldofmagneticreconnection.
SãoJosédosCampos,Brazil WalterD.Gonzalez
Chicago,IL,USA EugeneN.Parker
September2015
Preface ix
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