Analysis and interpretation of a fast limb CME with eruptive prominence, C-flare and EUV dimming

0.58 MB·English

by  Serge Koutchmy

Astronomy&Astrophysicsmanuscriptno.aa20078311 (cid:13)c ESO2008
February2,2008
Analysis and interpretation of a fast limb CME with eruptive
prominence, C-flare and EUV dimming
S.Koutchmy1,V.Slemzin2,B.Filippov3,J.-C.Noens4,D.Romeuf5,andL.Golub6.
1 Institutd’AstrophysiquedeParis,CNRSandUniv.P.&M.Curie,98BisBoulevardArago,F-75014Paris,France
8 e-mail:[email protected]
0 2 P.N.LebedevPhysicalInstitute,Leninskypr.53,Moscow,119991,Russia
0 e-mail:[email protected]
2 3 PushkovInstituteofTerrestrialMagnetism,IonosphereandRadioWavePropagation,RussianAcademyofSciences(IZMIRAN),
TroitskMoscowRegion,142190,Russia
n
e-mail:[email protected]
a
4 OMPandPicduMidiObservatory,France
J
e-mail:[email protected]
7 5 C.R.I.ClaudeBernardLyonIUniversity,O.A.-Fiducial,France
1 e-mail:[email protected]
6 Harvard-SmithsonianCenterforAstrophysics,60GardenStreetMS58,Cambridge,MA02138USA
] e-mail:[email protected]
h
p
ReceivedJuly00,2007;accepted
-
o
r ABSTRACT
t
s
a Aims.Coronal mass ejections or CMEs are largedynamical solar-corona events. The mass balance and kinematics of afast limb
[ CME,includingitsprominenceprogenitorandtheassociatedflare,willbecomparedwithcomputedmagneticstructurestolookfor
theiroriginandeffect.

1 Methods.Multi-wavelengthground-basedandspaceborneobservationsareusedtostudyafastW-limbCMEeventofDecember2,
v 2003,takingintoaccountbothonandoffdiskobservations.ItseruptingprominenceismeasuredathighcadencewiththePicduMidi
6 full Hαline-fluximaging coronagraph. EUVimages fromSOHO/EITand CORONAS-F/SPIRITspace instruments areprocessed
4 includingdifferenceimaging.SOHO/LASCOimagesareusedtostudythemassexcessandmotions.Computedcoronalstructures
7 fromextrapolatedsurfacemagneticfieldsarecomparedtoobservations.
2 Results.Afastbrightexpandingcoronal loopisidentifiedintheregionrecordedslightlylaterbyGOESasaC7.2flare,followed
. byabrighteningandanaccelerationphaseoftheeruptingmaterialwithbothcoolandhotcomponents.Thetotalcoronalradiative
1
fluxdroppedby∼7%inthe19.5nmchannelandby4%inthe17.5nmchannel,revealingalargedimmingeffectatandabovethe
0
limbovera2hour interval.Thetypical3-partstructureobserved1hourlaterbytheLascoC2andC3coronagraphs showsacore
8
shapedsimilarlytotheeruptivefilament/prominence.ThetotalmeasuredmassoftheescapingCME(∼1.5·1016gfromC2LASCO
0
observations)definitelyexceedstheestimatedmassoftheescapingcoolprominencematerialalthoughassumptionsmadetoanalyze
:
v theHαeruptingprominence, aswellasthecorresponding EUVdarkeningofthefilamentobservedseveraldaysbefore,madethis
i evaluation uncertain byafactor of 2. Thismass budget suggests that theevent isnot confined totheeruption region alone. From
X
thecurrentfreeextrapolationwediscusstheshapeofthemagneticneutralsurfaceandapossiblescenarioleadingtoaninstability,
r includingthesmallscaledynamicsinsideandaroundthefilament.
a
Keywords.Sun:activity–Sun:filaments–Sun:prominences–Sun:coronalmassejections(CMEs)–Sun:flares
1. Introduction 2000;Cremades&Bothmer2004;Gopalswamy2006)thisques-
tion has not been systematically considered and no clear an-
CoronalMassEjections(CMEs)wereoriginallydefinedaslarge swerexists.OnepossibilityisthatthemassoftheCMEcomes
coronaldynamicalphenomena(coronaltransients)propagating fromarelatederuptingprominence(EP)anditsimmediatesur-
outwardinthefieldofviewofwhite-light(W-L)externallyoc- roundings. This assumption was seriously considered recently
cultedspace-bornecoronagraphsandoftenshowingthreeparts andpromptedanotherquestion:whatisthemassoftheEP(see
(seeWagner1984).Theirprimarypropertyisthemasstransport Gilbert et al. 2005, 2006)? However, the general consensus is
ofapresumablycoronalmassoriginallysituatedbehindtheoc- thatonlythecoreofthe3-partCMEcorrespondstothepromi-
culting device, toward the externalpart, without specifyingthe nence.
originofthismassrevealedbytheW-Leventduetothescatter-
ingonfreeelectrons.Modelershadtoaddressthefundamental
Adistinctionhasbeenmadein consideringthepresumably
question:fromwheredoesthislargeamountofcoronalplasma
more importantfast CMEs, usually related to a flare and more
originate?AlthoughmanystatisticalstudiesofCMEswerepub-
likely to be geoeffective and with space weather implications
lished in recent decades (among the latest, see Vourlidas et al.
(seee.g.Baoetal.2007).TheEPconnectionisthensometimes
omittedin favor ofa discussionof theoriginof solar energetic
Sendoffprintrequeststo:S.Koutchmy particlesthatcontributeonlyalittletothemassbudget.
2 S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence
CMEsareoftenassociatedwitheruptingfilamentsorpromi-
nencesevenwhenconsideredfarfromtheSun(seeBothmer&
Schwenn1994).Inthelastfewyearsmanyinvestigationswere
undertakentostudytherelationshipbetweenprominenceactiv-
ity and CMEs in different wavelengths. Based on Hα observa-
tionsattheMaunaLoaSolarObservatory,Gilbertetal.(2000)
proposedaclassificationofactiveanderuptiveprominencesac-
cording to their kinematical properties (radial height, velocity
and acceleration). A separation between escaping prominence
materialliftingawayfromtheSunandmaterialreturningtoward
thesolar surfacewouldoccurin theheightrangefrom1.20R
⊙
to1.35R whichcouldberelatedtotheformationofanX-type
⊙
neutrallineinthisregion.
Gopalswamy et al. (2003) studied the temporal and spatial
relations between the signatures of prominence eruptions de-
tected in microwaveswith the NobeyamaRadioheliographand
white-light CMEs. It was shown that in most of the studied
eventstheprominencemovedpredominantlyintheradialdirec-
tion,withCMEsandEPsstartingatnearlythesametime.Jing
et al. (2004) presented a statistical study of filament eruptions
observed in Hα at the Big Bear Solar Observatory with other
phenomenaofsolaractivity.Theyfoundthatmosteruptions(>
50%)wereassociatedwithwhite-lightCMEs,activeregionfila-
menteruptionsbeingmoreassociatedwithflaresthanquiescent
filamenteruptions.BecauseoftheircloserelationshiptoCMEs,
EPs were regarded as one of the main sources of material in
themassbalanceofCMEs.Indeed,fromthetheoreticalmodel-
ingpointofview,themassoftheprominencecouldbeanissue
when consideringthe launchof the CME (Low et al. 2003) or,
more generally, its associated magnetic structure (see Chen et
al. 2006).Furtherout,therearestrongindicationsthatthe core
inthethree-partCMEstructureisassociatedwithaprominence
butthisrelationisnotdirect;multi-wavelengthobservationsare
needed.
EvaluationsoftheEPmassaretraditionallybasedonobser-
vations of the Hα absorption of the correspondingfilament on
the disk prior to eruption,where they are seen as dark objects.
Thedestabilizationoffilamentsappearsasasuddendisappear-
ance in Hα or a disparition brusque (DB) (Tandberg-Hanssen
1974;Soru-Escaut&Mouradian1990)whichcanbecausedby
an increase of the plasma ionization degree (thermal effect) or
which can also be a result of Doppler- Fizeau effects (dynam-
icalDB)includingadarkeningproducedbyrapidmassmotion
(Heinzel& Rompolt1987).With TRACE usuallya large,high
butfaint∼1MKloopmovesoutwardbeforeanythingelsehap-
pens.
Theapproachtoestimatingthehydrogendensityinfilaments
from Hα absorption was developed by Mein et al. (1996) and
Heinzel et al. (1999) who used the non-LTE cloud model with
optical thickness, Doppler width and velocity as input param-
eters. Because the hydrogen ionization degree in the non-LTE
modelisafreeparameter,thetotalmassofthefilamentcannot
bedeterminedunambiguously.Whentheprominenceisseenin
emission outside the disk, a more direct evaluation can be at-
tempted using both narrow passband W-L coronagraphicmea-
surementsandHαline-fluxemissionimaging(seeKoutchmy&
Nikolsky 1981). To make filtergrams, a narrow passband Lyot
filterisusuallyusedandthedataneedadditionalcalibrationsto
takeintoaccountthebroaderlineprofile.
Fig.1. TheBBSO Hαimage(a)showingthezoomboxcorre- This problem was partly overcome by combining Hα ob-
spondingtotheMDImagneticmap(b)oftheAR10508region servationswithobservationsoffilamentsincoronalEUVlines,
with superimposedcontoursof filaments (red) from the BBSO where filaments are seen as dark objects on the backgroundof
the underlying corona, on the disk or even outside the disk.
Hαimage;(c)EITimageoftheboxregionat195Å.Allimages
EUVobservationsoffilamentswerestartedwiththeSkylabmis-
aretakenonNovember26,2003.
S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence 3
HerewereportonalargeW-limbevent,whichoccurredon
December 2, 2003, 9-14h UT, in the vicinity of the old multi-
polarregionAR10508whichwaswellobservedearlierbutwas
still on thedisk at the time ofthe CME. We analyse the obser-
vationsoftheprominenceeruptiontakeninHαfull-lineimages
with the HACO coronagraph of the Pic du Midi Observatory
(Romeufetal.2007),imagesofthesurroundingcoronainEUV
withSOHO/EIT(Delaboudiniereetal.1995),andCORONAS-
F/SPIRIT telescopes (Zhitnik et al. 2002), and W-L images of
theassociatedCMEtakenwiththeLASCO(SOHO)C2andC3
coronagraphs.We discussindetailthe spatialandthetemporal
developmentofthe eruption,evaluatethekinematicsandespe-
ciallythemassbudgetoftheCME-relatedphenomenonandwe
proposeapossiblescenariooftheevent.Thisapproachisquite
similar to the early work of Plunkett et al. (2000) where a fast
limbCMEeventwithanEPwasstudied,althoughnoflarewas
reported (possibly because the region was already beyond the
limb).Herewepayspecialattentiontothemassbudget,includ-
ing the measurementof the EUV dimming effect, and we pro-
poseamodelapplicabletothisparticulareventbasedonacom-
Fig.2.PartialframefromanHαfiltergramtakenbeforetheerup- putedmagneticfieldcontexttodescribethewholeevent,instead
tionfromtheInternationalHαNetworkand,atleft,thededuced ofproposingauniversal2.5Dmodel.
setofcalibratedisophotesusedto evaluatethe massoftheoff-
diskprominence.Notethelevelsofscatteredparasiticlightout-
side the solar disc (some typicalintensities are shown near the
bottompart).
2. Observations
2.1.Thecontext
sionandthencontinuedbySOHO(EITandCDS)andTRACE.
Batchelor&Schmahl(1994)interpretedtheEUVabsorptionof Agroupofthreemassivefilamentswasobservedoneweekbe-
coolobjectsasacontinuumabsorptionofthecoronalradiation fore the eventby the Global High-ResolutionHα Network ob-
by neutral H, and by neutral and ionized He dependingon the servatories (BBSO image in Fig. 1a) in the vicinity of NOAA
wavelength. Kucera et al. (1998) and Penn (2000) used CDS AR 10508, which is one rotation after the famous AR 10486
dataforprominencediagnosticsandobtainedacolumndensity thatproducedextremelypowerfulX17flaresonOctober29and
of neutral hydrogenH of ∼ 4·1017 −1018 cm−2. Mein et al. X28 on November 4 during the preceding Carrington rotation.
(2001)haveshownthatacombinationofHα,Ca(8542Å)and Thelargestfilament(whichwewillexaminefurther)locatedto
TRACE 171 Å data may yield a more self-consistent determi- thenorthofthecenteroftheAR,wasdividedintotwopartsby
nation of the neutral hydrogen column density, of the electron astrongnegativemagneticfieldpatchseenwithMDI(Fig.1b).
densityandoftheelectrontemperature. The filament was seen in all EUV wavelengths with EIT and
Heinzeletal. (2001)andSchmiederetal.(2003, 2004)no- with SPIRIT in the 175 Å and 304 Å bands as a dark fea-
ticed that filaments are more extended in EUV spectral lines ture.Incoronallinesthefilamentwascoveredbyoverlayinghot
loopsoftheactiveregion.Duringaweek,fromNovember25to
with wavelengths below the hydrogen Lyman-continuum edge
December2,GOESobservedmorethan20X-rayflaresinthis
(912Å)thaninHαandtheyintroducedtheterm“EUVfilament
active region and the filament was not yet destabilized by the
channel”(EFC) to describetheir observations.A spectroscopic
flares.
modeloftheEUVabsorptionoffilamentsandprominenceswas
suggested by Heinzel et al. (2003a, 2003b), Anzer & Heinzel We estimatethegeometricalparameters,intensitiesandde-
(2005), and Schwartz et al. (2006). The method takes the ab- rived physical values of two parts of the filament marked in
sorption of EUV-line radiation by the Lyman continuum self- figure 1b (top half) as f1 and f2, from its Hα image taken on
consistentlyintoaccount,aswellasthevolume-blockingeffect November 26, 2003 at 17:57:25 UT. The data are shown in
that is potentially important for coronal lines. A similar tech- Table 1 (the thickness D was not measured and was taken as
niqueforderivingprominencemassfromEUVabsorptionfea- equaltotheaveragevisiblewidth).Takingintoaccountthatthe
tures was developed by Gilbert et al. (2005, 2006). However, measuredintensityisthesumofpartlyabsorbedbackgroundand
when the EUV filament is seen as a prominence on the off- foreground,weestimatedtheopticalthicknessinHα.Assuming
diskcoronalbackground,oftenanedge-brighteningaroundthe the mean temperature of the filament body (8000 K) and fol-
prominenceisobserved,stronglysuggestingthatheatedcoronal lowingtheapproachofHeinzeletal.(2003a),weestimateτ
912
materialisconcentratedattheperipheryoftheprominence.De which gives the neutral hydrogen density n , electron (H-ion)
1
Boeretal.(1998)analyzedtheperipheryofaprominenceusing densityn andthetotalhydrogendensityn .Thisgivesthemass
e H
transitionregion(TR)lineemissionanddescribesthisenhanced ofbothpartsoftheHαfilament M = 1.3·1015 g.According
Hα
emissionwithnon-thermalbroadeningsandvelocitiesreaching toAulanier&Schmieder(2002),andHeinzeletal.(2003b),the
valuesupto45km/s,whichisconsiderablyhigherthanwhatis EFCdefinedabovecontainsanadditionalmassof50-100%of
observedusingtheprofilesofcoollinesinsidetheprominence. theHαfilamentmass,althoughwearenotsureweseetheEFC
DuringtheonsetofourEPweobserveda similarcoronaledge in our case, see Fig. 1. The total mass of the filament material
brightening. (Hα+EFC)isthenestimatedasM =(2.3±.3)·1015g.
F
4 S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence
Fig.3. Active phase of the prominence eruption seen with HACO in Hα (a)-(c) and in EIT 195 Å (d)-(f). The arrow marks the
possibleplaceofemergenceofthemagneticloop.Inthebottompanels,thetimevariationsofthetotalfluxinHαmeasuredwith
HACO(g)and,overthefulldaytimeinterval,inX-rays1-8ÅmeasuredwithGOES-12(h).
2.2.Theeruptingprominenceandtheflare inthefullHαlinewiththeHACO(H-AlphaCOronagraph)im-
ageratPic duMidiobservatory(seeRomeufetal. 2007foran
On December 1 all day and on December 2 before 09:00 UT, exhaustive description of HACO observations) with a cadence
a filament previously studied on the disk was observed on the of15 s. Abovethe limb a prominenceis seenin Hα asa lumi-
westlimbinHαandinEUVlines(withSPIRITandEIT)asa nous object because of its large opacity to UV and EUV radi-
quiescentprominencewithacenterofmasslyingataheightof ation from the corona, the TR and the chromosphere (Heinzel
∼63Mm.Lateritbecameaneruptingprominence(EP)thatwe &Rompolt1987).HACOcollectsthefullfluxproducedbythe
studiedindetail.After09:10UTtheprominencewasobserved Hαline(spontaneoustransition3-2afterlevel3isexcited),in-
S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence 5
Table1.Geometricalandphysicalparametersofthefilament.
Filamentpart D,cm S,cm2 V,cm3 τ τ n ,cm−3 n ,cm−3 n ,cm−3 M ,g
Hα 912 1 e H Hα
f1 1.1·109 2.2·1019 2.2·1028 0.48 49 7.9·109 1.2·1010 2.0·1010 1.0·1015
f2 1.1·109 3.9·1018 3.9·1027 0.85 96 1.5·1010 1.6·1010 3.1·1010 2.9·1014
wellwithinthepass-bandofthefilter,providedtheirtransverse
componentsdonotexceed70km/s.
We looked into the details of these short brightenings us-
ing a simultaneous histogram analysis of each consecutive im-
age taken at high rate (15 s cadence;not shown here),keeping
inmindallpossiblevariationsofinstrumentalandatmospheric
origin(seeing),to concludethatthe prominencewas reallyag-
itated “inside”. But the details of this analysis are beyond the
scopeofthisworkandwepresenthereonlythesummarycurves
shown in Fig. 4 with some small scale rapid variations which
couldpartlybeproducedbyseeingeffects.Wealsonotethatthe
increase ofHα flux is difficultto attribute to a suddenincrease
ofthe densityorofthe pressureinsidethe prominence:neither
themorphologynorthekinematicsoftheEPsuggeststhis.
AnincreaseoftheturbulenceinsidethebodyoftheEPgiv-
inganincreaseinHαemission,precedinganyaccelerationup-
Fig.4.Temporalvariationsinrelativeunitsofi)thefullHαline
ward(ordownward)ofthemainpartsoftheEP(seeFig.4),is
flux, ii) the effective surface area of the prominence (inside a
anovelfeaturewhichtellsussomethingabouttheheatingpro-
closed contour drawn at half intensity) and iii) the computed
cessesoftheEPbeforeitslaunch.Themeasuredbehaviorofthe
heights of the center of gravity and of the upper edge of the
variationsof the effective surface (Fig. 4) of the prominenceis
prominence;after 10:30UT the valuesare less meaningfulbe-
an additionalargumentin favor of the “turbulent”scenario be-
causetheintensitiesoftheEPdrasticallydrop.Thephaseshifts
cause of the observedphase shift between the differentcurves:
ofthetemporalvariationsofthesedifferentparametersareillus-
i) variationoffluxes,ii) variationsofthe effectivesurfacesand
trated.
iii) themotionofthe centerofgravityoftheprominence,plot-
ted in Fig. 4. One possibility to explain this increase of turbu-
lenceinside the prominenceis to considerprocessesleadingto
shortperiod(3to6min)oscillationswhichwouldputitsthreads
dependentlyof the dynamicstate of the emitting elements(see
intorapidtransversemotion.Subsequently,asignificantrateof
Fig. 3) thanksto the broad width (0.25nm) of the interference
dissipation(thermalheatingduetowavedissipation,forexam-
filterusedbythisinstrument.Thisisincontrasttomostinstru-
ple)wouldthenincreasetheionizationratioandultimately,will
ments taking Hα filtergrams(see Fig. 2) which are affected by
maketheEPdisappearinHαandmakeitthenappearinemis-
theDopplershiftsinvariablyoccurringduringtheonsetofanEP.
sionin the hotterEUV lines. Anargumentin favorofthispro-
Inadditionthelevelofscatteredparasiticlightisgreatlyreduced
cess comesfromthe examinationof the TRACE moviesof fil-
inHACO,comparedtousingafiltergram(seeFig.3a-c).
aments seen in absorption in the 171 Å coronalchannel. They
At 09:13 UT we observed a new bright small expanding
illustrate several cases of agitation phenomena occurring be-
coronalloopemerginginthecenterofAR10508(indicatedby
fore the activation (rising) leading to ionization and eruption
anarrowinFig.3d),”striking”theprominenceanddestabilizing
(see the filament movies produced by the Lockheed group; A.
it.Figure3a-fshowsthemostimportantstagesofthisprocessin
Title,2006,personalcommunication)ofafilament/prominence,
Hα (HACO) and using EIT 195 Å observations. EUV images althoughthelimitedfieldofviewdoesnotalwayspermitafull
synchronouslyshow the expanding loop and increased heating evaluation of dynamical events linked to a CME. In TRACE,
ofthe gasaroundthe prominencebody(also calledthe periph- bright emission (Fe/ and Fe) is usually seen intermixed
ery,seedeBoeretal.1998),whichpossiblycorrespondstoapart withthedarkabsorptionduringtheeruption,notalongtimebe-
oftheEUVfilamentchannel.Atthesametimethebrightnessof fore(seealsoHerantetal.1991Figs.4,5and6).
theprominencebodyincreasedinHαtoitsmaximumvalue(at
09:35UT,seeFig.4).Thisispossiblyduetothegrowthofturbu- After09:41UTthebrightnessofourprominencedecreased
lence inside, which would then producea Doppler-brightening inHαandincreasedinEUVduetoheatingandionizationpro-
effectaffectingitssmallelements(threads),asGontikakisetal. cesses and it started to rapidly move outward, with the hottest
(1997)showedusingadetailedcalculationforthecaseofanEP. partdirectedtowardstheSun.At09:48UTtheGOESX-rayin-
Followingtheseauthors,thefullfluxinHαcouldbemagnified tensityreacheditsmaximumvaluecorrespondingtoaC7.2flare.
by a factor of 2 to 3, which corresponds to what we observed Figure3e,gshowsthelightcurvesofthetotalfluxinHα,mea-
in the body of the prominence for a short time, with turbulent suredwithHACO andinX-rays(1-8Å)measuredwith GOES
velocitieswhichkeepthecorrespondingshiftedlineprofilesstill 12.
6 S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence
Fig.5.EstimationoftheCMEmassfromLASCOC2images:(left)-theintegratedregionscorrespondingtothefrontalstructure,
thecoreoftheCMEandtothestreamer;(right)-theequivalentmasscorrespondingtotheshownintegratedintensities.
UT)aweakstreamerwasseennearbyat225◦.Asaresultofthe
CME development, the streamer at the periphery of the CME
wasdeflectedtotheSouthanditsbrightnessgraduallyincreased
withtime.TheCMEhadatypicalthree-partstructure-afrontal
bright loop, a dark cavity and a bright core (see Fig. 5). The
shapeofthecoreresembledtheshapeoftheheatedEFCin195
Å (Fig. 3f). After 11:06 UT the frontal structure and, 20 min
later,thecoreoftheCMElefttheC2fieldofview.InC3thefull
CMEwasseenonlyinoneframeat12:18UT.
AccordingtotheLASCOcatalogue,theCME(frontalstruc-
ture) moved in the C2 and C3 from 4 to 25 R with a nearly
⊙
constantvelocity of 1393 km/s. At 6R the core movedwith a
⊙
velocityof942km/s.Thepointscorrespondingtothecoreinthe
height-timegraphmatchwellthesamelineasthelastpointfor
the prominence, which suggests a close relationship. The acti-
vationandthemotionoftheprominencestartedatleasthalfan
hourbeforetheCMEonsetdeterminedfromalinearinterpola-
tionoftheLASCOpoints.
3. Massloadingandkinematicsoftheeruptionand
theCME
Thefirstcomponenttoconsideristhemassdirectlyinjectedor
loaded by the EP and its surroundings. We discussed in Sect.
2.1thedeterminationofthemassoftheHαfilamentwhichwas
observed well before in the active region underlying the event
(Fig. 1) and evaluated its mass, including its immediate sur-
rounding,as(2.3±.3)·1015g(thisvaluepossiblymaybedoubled
Fig.6.Height-timeprofileoftheprominence,thefrontalstruc-
duetoturbulence).
ture and the core of the CME (a); profile of the velocity and
Weusedseveralmethodstoevaluatethemorerelevantbulk
accelerationoftheCMEcore(b).Theshadedareacorresponds
massoftheprominencebecomingtheEPjustpriortoitslaunch
tothetimeintervalwheretheeruptivematerialwasoutoffields (Fig. 2 and Fig. 3a). The effective surface area of the promi-
ofviewoftheinstruments.
nence is easy to measure. Then, we compared its average in-
tensity and morphologywith those of typicalprominencesthat
were measured with the aim of determining typical masses of
2.3.TheCMEinW-L
prominenceswith the large 52 cm aperture coronagraphof the
TheCMEassociatedwiththeeruptionappearedintheLASCO high altitude station near Kislovodsk. Narrow pass-band filters
C2fieldofviewafter10:50UT.Beforethistime(e.g.at10:26 (FWHM of .5 nm) in W-L (a continuum window near 607.3
S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence 7
nm) and around Hα were used to perform a photometric anal- Theestimatedvaluesofmassescorrespondingtothetimeof
ysis(Koutchmy&Nikolsky1981).Wefoundatypicalelectron thefullCMEexpansionintheC2fieldofview(11:26UT)are:
density integrated along the l.o.s. (or “column” density) of the for the frontalstructure 8·1015 g, forthe core6.6·1015 g, for
order of 2.5· 1038 cm−2. Assuming an ionisation rate of 50% thestreamer2·1015 g;forthetotalamountincludingallCME
overthe103Mm2effectivesurfacewehaveamassof1.2·1015 parts and the streamer 1.1 · 1016 g. The values for the frontal
g.Insidetheprominencetheionisationratiocouldbelowerand structure and for the core partly include the moving streamer
the estimated mass of the prominencewill increase by a factor componentbecauseitis difficulttoclearlydistinguishbetween
of2to4. them. A more realistic estimate is obtainedafter subtractionof
thestreamermassfromeachcomponent,whichgivesamassof
The second method we used takes advantage of intensity the frontalstructureof 6·1015 g,for the core4.6·1015 g. The
measurementsdoneonthe filtergramshownin Fig.2, bycom-
sumofthesevaluesgivesafullCMEmassforC2(withoutthe
paringthe isophote intensity levels overthe prominenceimage streamer)of10.6·1015 g.ThetotalCME massvalueforC3at
with the simultaneouslyobserveddisk intensities. We then can 13:42UT(R = 25R )isestimatedas1.5·1016 g,showingthat
⊙
obtaintheintegratedl.o.s.amountofplasmawithneutralhydro-
theprocessofCMEdevelopmenteffectivelycontinued.
geninlevel2,andthenassumptionshavetobemadeconcerning
Thetotaleruption/CMEprocesscanberoughlydividedinto
thethermalequilibriumamongthelevelstodeterminetheabun-
threestages:activation,eruptionoftheprominence,andpropa-
danceofHatgroundlevel1,wheredensitiesareseveralorders
gationoftheCMEintheLASCOfieldofview.Betweenthelast
ofmagnitudehigher,etc.Atlocalthermo-dynamicalequilibrium
momentwheretheprominencewasseen inEUVor Hα(10:24
(LTE),itwilldependontheexcitationtemperature(Gouttebroze
UT)andthefirstappearanceoftheCMEintheLASCOC2field
etal.1993)whichwetaketobeoftheorderof6000K.Thede-
ofview(10:50UT)thereisa’greyzone’wherethepositionof
ducedcolumndensityfromtheaveragedvaluesofHαfluxesof
the erupting matter and the parameters of its evolution are not
Fig. 2 gives an overallmass, taking into account the extension
possibletodetermine.
shownbyisophotes,quiteclosetothemassdeducedfromW-L
Wemeasuredthepositionsofthemovingprominenceseenin
coronagraphicobservations,when a 50%ionisation ratio is as-
absorptionfromtheimagestakenwiththeEITandtheSPIRIT
sumed(seealsoKoutchmy&Nikolsky1981).Itcouldmeanthat
telescopes (from 09:00 UT to 10:24 UT) and combine it with
thisassumptionisnottoofarfromreality.However,theionisa-
the measured positions of the CME core in the LASCO C2
tion ratio is a matter of discussion: it is certainly not uniform
images. The height-time profiles of the prominence/core and
inside the prominence (and even across the section of a single
frontalstructureareshowninFig.6a,thederivedvaluesofve-
thread) and at least at the peripherywhere Hα emission disap-
locityandaccelerationofthecore-inFig.6b.Thedottedlinesin
pears,theratioiscloseto100%.Further,theassumptionofLTE
thesefigurescorrespondtotheprojectedCMEonsettimefrom
is certainlynotsatisfied, andfinally the temperatureis notuni-
the LASCO CME catalogue (http://cdaw.gsfc.nasa.gov/CME
form(seeWiehretal.2007).Inthisrespect,whattheEPregion
list) where it was derived from the height-time profile for the
lookslikeusingdifferentEITchannelsisimportant.The304Å
frontalstructureusingalinearapproximation.
image of He+, taken several hours before the eruption, shows
the prominence in absorption but surrounded by rather strong
emission;itissimilarbutweakerinthe171Å(Fe/)channel. 4. EUVdimmings
In the 284 Å channel where the coronal temperature is much
higher(Fe),itisnotlikethis:althoughtheprominenceisalso In general, dimmings (areas of temporarily reduced emission
seeninabsorption,noenhancementisseenattheperipheryand measure) in EUV or soft X-ray images appear at the places of
thecoronalemissionismoreextended.Thistellsusthattheex- thecoronalplasmaoutflowduringaneruptionleadingtoaCME
tendedsurroundingofthe EPisanimportantpartofthewhole (e.g. Zhukov & Auchere 2007). It is interpreted as a density
eruptionandthatthe massof a largepartofthis areahasto be depletionassociated with theCME initiation(Hudson& Webb
takenintoaccount(seethediscussionofthedimmingeffectbe- 1997;Zarroetal.1999andothers).Theprocedureofimagepre-
low). processingandofselectionofthedimmingregionsweusedhere
wasdescribedindetailelsewhere(Chertoketal.2004;Chertok
In view of the large dispersion foundwhen trying to deter- &Grechnev2005;Slemzinetal.2005,2006).A detailedanal-
minethemassoftheprominencefromtheobservedHαflux(we ysis of dimmings and their relationship with CMEs have been
donotdiscusserrorsproducedbyusingaveragedvalueswithout carriedoutinmanypapers(e.g.Harra&Sterling2001;Harrison
goingintothedetailsoftheopticalthicknessvariationsandvari- etal.2003;Grechnevetal.2006andsoon).Mapsofdimming
ationsofthe profileofthe line),werefrainfromgivingformu-
regionswe obtained in 195 Å and 175 Å are shown in Fig. 7a
laeandnumericalresults,asidefromtheroughestimatesgiven
and Fig. 7b. Graphs in Fig. 7c display the light curves of the
above.Our conclusionis thatmorecoronagraphicobservations
total dimming intensities relative to the total intensities in the
of prominences are needed, such as observing simultaneously original(notdifferenced)nominalimages. The lightcurvesfor
theHαfluxandtheKCafluxtodeduceaparametersensitive bothcasesaresimilar:theyreachedamaximumat∼09:30UT-
to theionisationratio of H. Themethodpromotedin EUVby
10:00UTbeforetheCMEonset,thendecreasedtoaminimumat
Gilbertetal.(2005,2006)shouldalsobedeveloped(uptonow,
11:30UT-12:00UT.Thedropofintensityinthedimmingarea
theirsampleofprominencesgavemassesnotexceeding1015g).
relative to the total solar intensity before the eruption is large:
We also evaluated the mass of the CME using the LASCO in195Åitisabout7%,in175Åitisabout4.5%.Thespectral
imagesandthestandardSolarSoftprocedures,whichincludethe responsefunctionsofbothbandsarequitesimilarexceptthata
allocationof regionsof interestoverwhich intensitiesare inte- small,pronouncedhotcomponent(10-15MK)existsinthe195
grated.Ineachimageweseparatelytreatedthreeregions,which Åcase.
correspond to the frontal structure, the core and the streamer Wenotethatthebeginningofthegradualdimmingintensity
(Fig. 5a). The plots of the calculated masses are presented in decrease in 195 Å (Fig. 7c) corresponds to the moment of the
Fig.5b. launchoftheprominence(dash-dotlineinFig.7c)andthemax-
8 S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence
Fig.7. Left and center panels - EUV dimmings in the SPIRIT 175 Å and EIT 195 Å difference images. Right panel - the total
intensityinthedimmingarearelativetothetotalintensityofthenominalimages.DashedlinecorrespondstotheprojectedLASCO
CMEonset(10:15:50UT).
imumofintensityoftheX-rayflare.IfweassumethattheEUV where B is the normalmagnetic-fieldcomponenton the plane
n
dimmingisassociatedwiththeformationofthefrontalstructure, S and r is the radius vector from some pointon the surface to
onecanconcludethatboththefrontalstructureandthecoreof agivenpointinthecorona.Zagnetkoetal. (2005) showedthat
theCMEwereinitiatedverycloseintime(within5-10min). the prominence material is mainly concentrated at the surface
that passes through the apex of the field line arches which is
a magnetic neutral surface. Recall that the systematic inclina-
5. Interpretation:themagneticfieldstructureand tion of the bodies of large quiescent prominences at moderate
thefilamentequilibrium latitudestoward the west, which had beenwidely describedby
d’Azambuja&d’Azambuja(1948),wasexplainedbythepecu-
Thereisnodoubtthatthefilamentdestabilizationanditserup-
liarities of the structure of the large-scale magnetic fields. We
tionwere relatedto the propertiesandthe changesof the mag-
calculated the coordinates of the neutral surface in AR 10508.
neticfieldintheactiveregion.WefirstnotethattheCMEmor-
Figure 8 shows the projection of the magnetic neutral surface,
phology (see Fig. 5) seems to fit one of those identified by
asitshouldlooknearthelimb,calculatedabovetheneutralline
Cremades& Bothmer (2004), where the observedmorphology
relatedto thestudiedfilamentuptothe heightof150Mm.We
seemstobeconsistentwithwhatisexpectedfortheneutralline
cancomparetheshapeofanearlysemicircularlooplyinginthe
locationandthepositionoftheeruptionnearthelimb.However,
neutralsurface(Fig.8, right)withthe shapeoftheprominence
thecoronalmagneticfieldisnotmeasurednorevenqualitatively
attheearlystageoftheeruption(Fig.3b-c)whentheloopofthe
observed.Accordingly,thispartoftheworkismainlybasedon
eruptiveprominenceroughlyconservesitsinitialform.Atequi-
extrapolationsmadefromthesurfaceoftheSunandonguesses
librium,theprominenceloopshouldbelocatedneartheneutral
of the role of the magnetic field. The position of the active re-
surface,hencethefrontlegoftheprominenceshouldbecurved
gion,close to the limbon December2, wasfavorableformea-
andinthemiddlepartnearlyparalleltothesolarsurface,while
suringtheplasmadensitydistributionandthevelocityofcoronal
thebacklegshouldbemorestraightandtiltedfromthevertical
structuresbutmadeitalmostimpossibletoseethechangesinthe directionatanangleofabout30◦.Thisisqualitativelythesame
photosphericmagneticfield.Inordertoguessthemagneticcon-
aswhatweseeinFig.3b-c.
figurationintheeruptingregionwestartedfromthetimewhen
Then we found the limiting height of the filament equilib-
theregionwasnotfarfromthecenterofthedisconNovember
riumh bysolvingtheequation(Filippov&Den2000,2001)
25. c
We calculatedthe current-freecoronalmagneticfield1 B in dB B(h )
thevicinityofthefilamentusingthephotosphericmagneticfield =− c . (2)
dh(cid:12) h
measurementsfrom SOHO/MDI. As the regionof interest was (cid:12)(cid:12)hc c
(cid:12)
notlargecomparedwiththewholesurfaceofthehemisphere,we (cid:12)
This parameter is derived from the vertical stability condition
consideredtheboundaryasaflatsurfacerestrictedbythesizeof
in the inverse polarity filament model (Van Tend & Kuperus
the active region containing the main magnetic concentrations.
1978; Molodensky & Filippov 1987; Forbes & Isenberg 1991)
We used the well-known solution for half-space with a plane
andreflectsthescaleheightofthemagneticfieldofphotospheric
boundary:
sources.WecalculatedthelimitingheightusingtheSOHO/MDI
magnetogramsofNovember25,27,and29.Theresultsforthe
1 B (x′,y′,0)r
B= n dx′dy′, (1) twoformerdaysareverysimilar.Figure9showsthecalculated
2πZ Z r3 neutralline attheheightof6Mm,wherethe fieldis smoothed
S enough, overlaid on the photospheric magnetogram. The fila-
1 Generallyspeaking, thepresence ofanon-potential fluxropeisa ment that erupts on December 2 is also shown as a white con-
necessarypartofthemodel.Aquitesimilarapproachwasrecentlyat- tour.Inthe middlepartofthe filamentlength,whereitsaxisis
temptedinthecontextofanactiveregion(vanBallegooijen&Mackay ratherstraight,thelimitingheightishigherthantheverticalsize
2007). of our calculation domain (150 Mm). Near the filament ends,
S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence 9
Fig.8. Projection of the magnetic neutral surface in the AR
10508 on November 25, as it should look near the limb, cal-
culatedabovetheneutrallinerelatedtotheeruptiveprominence Fig.9. The neutral line calculated at a level of 6 Mm above
(left),andthesideviewofalooplyingintheneutralsurfacethat thephotosphere(yellowcontours)overlaidonthephotospheric
modelstheeruptiveprominence(right). MDImagnetogramobtainedon25November2003at19:12UT
withintheareausedastheboundaryconditionforcoronalmag-
netic field calculations. The filament position taken from the
the curvature of the neutral line increases. This means that the BBSOHαfiltergramfor16:45UT25November2003isshown
local scale of the photospheric magnetic field is smaller there. asaredcontour.
Inaccordancewiththereducedfieldscale,thelimitingheightis
lowerand reaches∼ 60Mm. However,nearthe filamentends
fieldlinesareanchoredinthephotosphereandthemagneticten- dance with the shape of the neutralsurface, the fore leg of the
sionplaysanimportantrole,whereasEquation2 doesnottake archismorecurved.Thearchapexwasslowlyascendingduring
intoaccounttheanchoringofthefilamentlegs. severaldaysbeforetheeruptionandreachedaveryhighaltitude
On November29 the AR 10508 was close to the limb and byDecember2.Wenotethataquitesimilarschemahasbeenre-
the magnetic field measurements became unreliable. We then centlyproposedbyAlexanderetal.(2006)todescribewhathe
usedaspecialproceduretoobtainthecomponentnormaltothe calleda“failed”filamenteruptionwithaflareandRHESSIhard
solar surface from the line-of-sightmeasurements (Den 2002). X-rayemissionsbutnoCME,sothatweshouldstillbecautious
Calculationsshowasmallloweringofthelimitingheightatthe withtheassociationofanEPandaCME.Ontheotherhand,this
filamentendsandasignificantloweringinthemiddleofthefil- scenarioagreesratherwellwiththerecentmodelofChenetal.
amentdownto40Mm.Thisvaluepossiblyreflectsthetendency (2006),proposedtodescribetheCME-EPphenomenon.
ofaloweringofthelimitingheight;however,ashasbeenmen- Thedarkfeaturevisiblebefore09UTinEUVimages,which
tioned,the initialphotosphericmagneticfield measurementsin coincides in space with the Hα prominence, overlaps the mid-
thisregionarenotreliable. dle part and the far leg of the filament arch along the line of
Observationsofthefilament(andthecorrespondingpromi- sight.Buttheactivationandtheascentoftheprominencebegan
nence)nearthelimbonNovember30andDecember1demon- near its fore leg. The rising part becomes bright in EUV as is
stratethatthefilamentwasstableuptoarathergreatheight.On observedinmanyeruptiveprominences(Filippov&Koutchmy
November30theheightofthefilamenttopcanbeestimatedas 2002),whilethefarpartofthearchisstillatrest.Thatiswhywe
35Mm,whileonDecember1-as50Mm.Thegreatestheight see risingbrightfeaturesonthebackgroundoftheratherstatic
on December 2, before the filament begins to ascend, was 120 darkformation.Thisfrontalpartofthefilamentbecomesclearly
Mm. This value is smaller than the limiting height on 25-27 visibleintheEITimagesinemissionat09:48UTandlater.Itis
November (more than 150 Mm) but greater than the limiting alsoclearlyseenintheHαimagesoftheeruptiveprominenceas
height on November 29 (40 Mm, possibly underestimated). It acurvedfeature(Fig.3b-c).
is not unlikely that the height of the filament reaches a limit- Theappearanceofmovingbrightfeatureswithinthebodyof
ing value not long before the eruption, as has been shown for anEPisconsistentwiththemechanismofheatingofthepromi-
severaltensoffilamentsbyFilippov&Zagnetko(2007).Webe- nencematerialproposedbyFilippov& Koutchmy(2002). The
lieve that the rising of the filament, possibly due to the growth sourceofenergyinthismechanismisthemagneticenergyofthe
ofanelectriccurrent(thatwedonotdiscusshere),withinaflux pre-eruptivemagneticconfigurationstoredinthefluxropeelec-
rope containingthe filament, up to the threshold of stability, is tric current and its interaction with the surrounding fields and
the main cause of the eruption. On the other hand, changes in plasma. The magnetic energy transforms into the macroscopic
the active regionmagneticfield can lower the threshold.When kineticenergyofthefilamentmotion,includingitsthreads.Part
the heightof thefilamentreachesthe limitingheightanysmall of this energy turns into heat throughcollisions inside the flux
disturbanceisabletoinitiatethebeginningoftheeruption. tubeafteranincreaseoftheturbulenceinside.Arathercomplex
The sequence of events observed on the west limb on structureofthefluxtubeisnecessaryforthispurpose.Someseg-
December 2 between 07:30 UT and 11 UT can then be inter- mentsof thetubeshouldhaveanupwardconcaveformto pro-
pretedintheframeworkofamodelofaneruptingfilamentloop. videthecounterflowacceleration.Wenotethatatypicaltwist-
Weassumethatthefilamentistheinternalpartofatwistedflux ing flux rope easily meets this requirementand that such twist
rope,whichhastheshapeofahalftorus,withbothendsstaying wasindeedobservedinseveralinstances(seee.g.Plunkettetal.
anchored in the chromosphere. The loop does not belong to a 2000;Koutchmyetal.2004;Sterling&Moore2004;Anderson
flatplanebutliesinthecurvedneutralsurface(Fig.8).Inaccor- etal. ?). Itis also the requirementdeducedfromthe latest the-
10 S.Koutchmyetal.:FastlimbCMEwitheruptiveprominence
oreticalanalysis ofthe flux ropemodelproposedfor CMEsby sightintegrationreachesa2-foldincreasedvaluerightabove
Chenetal.(2006). the limb with a correspondingincrease of the dimming ef-
fect. The dimming is in phase with the onset of the CME.
Approximately 5% or more of the corona is depleted, ne-
6. Conclusions
glectingthedepletionofthemassofthecoronaatverylow
(TR)and/orveryhighcoronaltemperatures.Thecoronaseen
We documenteda largeand fast coronallimb event,which oc-
curred on December 2, 2003, in the interval 9-14h UT, in the in the EIT 195 Å channel should indeed correspond to the
bulkofthemassbecauseitcorrespondstothemostprobable
vicinity of an old multi-polar region. Using observations ob-
temperatureofthecorona,sothatourestimateshouldnotbe
tainedonthegroundandinspacewithtwoEUVtelescopes,an
farfromthetruth.
HαcoronagraphandtheLASCO white-lightcoronagraphs,we
analysedaspectaculardynamicalphenomenonpassingthrough
Wealsofoundthattheeruptionledtoaspatialdeflectionand
differentstages:aquiescentfilamentinitially,thenaprominence
a brightening of the neighboring South-West streamer, which
withEUVbrighteningatitsperiphery,itsdynamicalandthermal
maygiveriseto anoverestimateofthe CME massby∼ 20%.
activation,a coronaleruptionwith a small flare and the launch
Further out toward both polar regions the deflections of struc-
of the eruptive prominence(EP) and finally the formation of a
turessuchasextendedplumesareclearlyvisibleasabackand
classicalthree-partfastCME.ThisCMEfitsratherwellwithin
forthquasi-coherenttransversemotion.Thisphenomenonwould
the frameworkof the so-called “standard model”, (see e.g. Lin
needspecialstudywhichisbeyondthescopeofthispaper.
2004).Herewehaveaddedseveralfeaturesthatwebelievecould
Finally our results suggest that greater attention should be
shed some light on the whole process, emphasizing the mass
paidtoregionsaroundtheEP,bringingaddedjustificationtothe
transport processes related to the EP and its coronal surround-
theoretical studies trying to describe the behavior of the coro-
ings.
nalmagneticfieldleadingtoCMEs.Howeveronlythefieldin-
From what we saw, the eruption process apparently started
sideprominencescanbeeasilymeasuredwithcoollinesandthe
withtheemergenceofanewmagneticloopstrikingthepromi-
Hanleeffect;animprovedprecisionHαcoronagraphcouldrou-
nenceanddestabilizingit.Thisledtoarapidheatingofthegas
tinelybeusedtoperformsuchmeasurementsathighspeed.
around the prominence body, which spatially corresponds to a
part of the EUV filament channel. The brightness of the body
oftheprominenceinHαatfirstincreasedtoamaximumvalue Acknowledgements. TheauthorsaregratefultoO.G.Denforcoronalmagnetic
fieldcalculations,toJ.-C.VialforclarificationsconcerningtheDopplerbright-
(at 09:35 UT) possibly due to the growth of turbulence inside
eningeffect,toG.Stellmacherforin-depthdiscussionsonthedeterminationof
whichproducesalargeDopplerbrighteningeffectand,accord- theprominencemassandtheinterpretation ofprominenceobservations, toC.
ingly, magnifies the Hα flux without the need to increase the Delanne´e,G.LawrencefordiscussionsonCMEsandtoA.Zhukovforcarefully
densities.Thisbrighteningevenprecedestheliftingofthecool looking atthe 1stdraft ofthe paper. This work was supported inpart bythe
RussianFoundationforBasicResearch(grants06-02-16424and05-02-17415)
prominence,whichseemstobe animportantnew featureto be
andinpartbytheNATOCRG940291.SOHOisaspaceprojectofinternational
takenintoaccountinfutureworkonCMEs.Wenotethatthisob- cooperationbetweenESAandNASAandwespeciallythanktheteamssupport-
servationwasmadepossiblebytheuseofacoronagraphhaving ingtheEITandtheLASCOobservationsforexcellentworkandprovidingtheir
a broad band filter and not a narrow band Hα filter as is usu- datatothecommunity.S.K.alsobenefitedfromCNESincollaboratingwiththe
LASCOteaminMarseille.TheHACOground-basedcoronalHαobservations
allydonewithasolartelescopetorejecttheparasiticlight.After
aresupportedbythe“ObservateursAssocie´s”teamsponsoredbyFiducialLTD
09:41UTthebrightnessdecreasedinHαandincreasedinEUV,
andbythe“ObservatoireMidi-Pyre´ne´es”.WearegratefultoM.Audejeanand
duetotheenhancedionizationprocessandpossiblyadissipation J.Guignardforcollectingthesequenceusedinthispaper.Wearealsoindebted
of the mechanicalenergyfromwaves or counter-flowmotions. totheinternationalHαNetworkforprovidingfiltergramstocoverthechromo-
Theprominencebegantomoveoutwardat09:48UT,whichco- sphericactivityin2003.
incides with the X-ray flare peak and would precede the CME
extrapolatedonsettime.
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