astrophysics and solar physics
DESCRIPTION
AACIMP 2009 Summer School lecture by Elena Podladchikova.TRANSCRIPT
The Moving Sun
Our Dynamic Star
Elena Podladchikova
Royal Observatory of Belgium
The Moving Sun
The Sun
Main source of heat and light.
Stability of the Sun – stable Earth conditions at geological scales.
Only for human eye Sun seems to be stable. In reality solar weatheris strongly variable.
The Moving Sun
Why study the Sun?
The Star presenting all the details of its surface.
Physical laboratory with the conditions impossible to reproduce on theEarth.
Influence on the terrestrial environment.
Activity of this Star produced the life on its planet - unique case.
The Moving Sun
SOHO/EIT
SOHO (Solar and Heliospheric Observatory) — spacecraft toobserve the Sun. Joint ESA-NASa mission.launch – 2 december 1995start ) May 1996Has 12 instruments onboard.Information about solar atmopshere, solar inetrior, solar
wind and solar corona activity.
One of the main instruments: EIT (Extreme ultravioletImaging Telescope)
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SOHO and STEREO
Continous Extreme Ultraviolet Imaging of theSun
SOHO is in the L1 Lagrange point
in the Solar-Terrestrial System
and goes around the Sun
simultaneously with the Earth.
ORBITSSTEREO has 2 spacecrafts
The "Ahead" spacecraft is flying completelyaway from Earth, and becomes a satellite ofthe Sun.
while the "Behind" spacecraft is flying in theopposite direction.
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SOHO and STEREO
SOHO and STEREO monitor the solar corona in 4 centralwavelengths
corresponding to the different temperaturesPARAMETERS
171 A 195 A
284 A 304 A
SOHO
Temporal Cadence
171 A: 1/h - 4/day
195 A: 15 -12 min
284 A: 1/h - 4/day
304 A: 1/h - 4/day
Spatial Resolution
1024 x 1024 pxls
STEREO
Temporal Cadence
171 A: ~2.5 min
195 A: 10 min
284 A: 10 min
304 A: 10 min
Spatial Resolution
2048 x 2048 pxls
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Outline
Introduction
Presentation of 3 aspects:
The Sun and “quiet” atmosphere (permanent regime)Manifestations of the Solar Activity.Solar influence on the Earth.
The Moving Sun
Ordinary yellow dwarf , type G2
Far from the center in the galactic disk of theMilky Way.
Phase of principal sequence:Since 4,5 milliards yearsFor 5,5 milliards yearsStable structure, but luminosity evolution ~ 10 % onmany milliards years (A-B).
The Sun: basic characteristics
Some Stellar Properties:Absolute magnitude: +4,5Effective Temperature: 5780 KMasse: 2 x 1030 kgRayon: 7 x 108 mGravitational acceleration atthe surface: 273,8 m/s2
Critical Ejection velocity: 617,7 km/s
Rotation: 25.38 d
The Moving Sun
Gravitational attraction of the planets ( orbits, tides )
Environment determined by solar electromagnetic radiation absorption(from gamma ray to infrared)
Influence by corpuscular emission (electrons, protons, -particles, etc.):Solar Wind: Mass lost 2 millions tonnes per second
Solar neutrinos :No influence, but direct information about nuclear reactions in the core.
The Multiple solar roles
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The Sun: structure
The Moving Sun
IFrom the core to transition region
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Quiet Atmosphere: introduction
Quiet Sun:Structures with weak time dependences (weak magnetic fileds)Large solar structures are little variable.
Active Sun:Variable phenomena.Brutal local deviations and transitory variations with respect to the quiet Sun.
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The different Faces of the quiet Sun.
4 principal layers:PhotosphereChromosphereTransition regionCorona (heliosphere)
Complete changing of physical conditions trough the layers:
The Sun does notappear the samein the differentwavelengths.
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Quiet photosphere: the granulation
The solar surface is covered bya pattern constituted by brightgranules separated by the darknetwork.
Imprint of subphotosphericconvective movements.
Size: 500 - 1500km (1")
Contrast: 10% ( T=150 K)
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Developed turbulence:At large scales: regime ofinetrtial convection(advection of heatdominates)At small scales: regime ofinertial conduction (heatdiffusion)
Velocity fieldGranulas center: ascendingInteragranulas: descendingVelocities: 1-2 km/s
Lifetime: <4 min>
Quiet photosphere: the granulation
Verticale structure of convective cells
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Photosphère calme: Points brillants et tubes de flux
Photopspheric Bright Points:
In the intergranulasB concentration in the descending flows
Flux tubes:Diameter: <100km
Magnetic Induction: 1000 à1500 G
Canals transportingconvective energy in theform of magneto-acousticshocks (Choudhuri, 1993)
Exponential growth of theamplitude (Kalkofen 1997)
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Magnetic network evolutionMagnetic fields are in the continuous evolution. Theirinteraction produce coronal heating.
Ephemeral RegionsSmall regions, no specificmagnetic orientation.Life time <4.4h>
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Photosphere: supergranulation
Organisation of thegranulation in the largerpattern
Mesogranulation:Scales: 5000-10000 KmTrace of turbulent dynamoat small scales (Cattaneoet al. 2001).
Supergranulation (Leighton1962):
Scales: 20 000 – 30 000KmLifetime: <12 h>
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Photosphere: faculaes
More hot regions
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The sunspots: proprties
Photospheric dark regions.Small spots without structure (pores):
Diameter <2500kmFor D >2500km, 2 zones:
Umbra :Diameter =10 - 15000kmIntensity = 5 - 30% IPhotosphere
Penumbra:D: 50000kmIntensity = 50 à 70 % IPhotosphere
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The sunspots: penumbra
Vertical field in the umbraHorizontal field in the penumbraRadial Filaments structureContinuous flow from the center to theborders: Evershed flow
Velocity: 1 - 2 km/s
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Sunspot Dynamics (Dutch Open Telescope)
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Sunspots: Magnetic field
Pass point of intensive magneticfield trough the thin photosphericlayer.Global dipolar structure:
N-S Polarity oriented E-WInclination with respect to equator:12°Group traversed by a neutral lineComplex topology
Intensity:Umbra: 3000 GPenombra: 1000 G
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The sunspots: properties
Lifetime: hours-monthsUmbra Temperature: 4000K
Quiet photosphere (5800K).Groupes ellongated in the E-W direction5 ° - 40° of latitude
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Sunspot Dynamics (SOHO/MDI)
Intensity
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Magnetic field and sunspots.
The sunspots are associated to intensive magnetic field (black andwhite spots on the magnetogram at right), that change continuously.
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The sunspots: Field hierarchy
Young groupes:Compact field
Old groupes:Dispersive flux
Permanent fields:Neutre diagonal line
Weak global field(10-4 T) that inversedwith the Hale cycle(22 ans)
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Sunspots and activity cycle
The number of sunspots varies with tehcycle of ~ 11 ans:
Cycle amplitude (maxima):48 in 1817 and 200 in 1958
~90 years modulationArchive Bruxelles):
30 cycles3 centuriesDaily index since 1850
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Sunspots and cycle: distribution in latitude (« Batterfly »)
Toward equator during the cycle:First spots: at 30° latitudeAt maximum: at 15°Last cycle spots: at < 5° from lthe equator (at 0°)Spots of 2 cycles coexistent during the activity minimum.
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Solar Dynamo: - effect
Ionized solar plasma:Plasma movements = large scale currents.
Magnetic field lines are frozen in the plasma under thesurface:
Poloidal (dipolar) magnetic field is elongated and coiled by thedifferential rotation -> amplification.Complete process - 8 m.Toroidal field production in the opposite direction
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Solar Dynamo: -effect
Magnetic lines torsion by the solarrotation, via the Coriolis force.Convection helicity generates aelectromotive force proportional tothis helicity and to toroidal magneticfield.
The energy of the dynamo comes fromkinetic energy of rotation and fluidmovement at small scales in theconvective zone.
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B puts pressure on the background medium:~ B2
Evacuation of plasma in the flux tube up to theequilibrium of the pressure with backgroundunmagnetized plasma:
The loop, less dense that ambient plasma go uptoward the surface:Loop formation in
During the rising - rotation by Coriolis:DIpole inclinnation (opposite sens)B helicity
During the cycle the emergent loops arereformed by the reconnection andfragmentation with global dipolar field:
Reconstitution of the initial poloidal field
Ascending and torsion of magnetic loops
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The dynamo in movement
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Looking at far side of the Sun
SOHO/MDI
Helio sesimology informs us about the far side of theSun. One can see here how the sunspot group (withintesive magnetic field) can be followed during manysolar rottaion. (Here the Sun is fixed and the observer ismoving.)
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Waves on the Sun: helioseismology
SOHO/MDI
Thousand of acoustic waves parcourentcontinuously the solar surface. One can hearthem accelerated 42000 times. Analysingthese waves one can investigate the SolarInterior and deduce for example the soundspeed.
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Looking IN the Sun
The helioseismology informs usabout Solar interior as well asabout changing structure ofsolar rotation. One can find therotation bands more fast (red)and more slow (green andbleu)
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Exterior Atmosphere
Chromosphereand
Transition Region
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The chromosphere: general structure
Much more dynamic medium,that the photosphere
Important spatio/temporalvariations of the emission.
Chromospheric network:Scales corresponds tosupergranulation: 20 – 30 000km.Enhanced emission on the granulaborders, concentration of strongmagnetic field (tubes de flux).
Brightenings around AR,correspondance with faculaes.
CaII K filtergram,Kitt Peak Obs., USA
TRACE, Ly
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Fine structure fine: the spicules
Surface covered by the vertical spouts (~100 000 on tehSun), the spicules:
At the limb: bright (spicules)Disk center: dark (mottles)
Inter-spiculaire space hot (106K) and not dense.Mass flux: 100 x the necessary flux to maintain the solatwind.
Essential role in the balance of mass flux in the solarwind.
Temperature: 4500KHeight: 5 000 – 20 000 kmSection: 500 kmEjection speed: 20 km/sLifetime: 5 à 10 min
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The chromosphere: heating source
The turbulent photopsheric convection provides energy to heat upper layers.It produces propagating acoustic waves:
Acoustic waves:In the unmagnetized interior of supergranulas.Excitation by the random vertical movement.Resonance chromopsheric cavity is on the level of cut-off frequency of p-modesaAt 5 mHz (P=3min).
MHD modes:Slow and fast Magnetoacoustic, Alfven.Excitation by the footpoints displacement.Transformation in shock waves.
Other sources:Macroscopic flows (Spicules)Current dissipation (reconnection magnétique locale)
Reviews: Narain & Ulmschneider (1990), Ulmschneider et al. (1991)
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Atmopsheric Model
Coronal heating problem: why is the corona so hot?
Vertical profile of temperature
and density in the Solar atmosphere
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Dissipation of magnetic energy & small scales
1. Heating by MHD waves
Dissipation of Alfvén waves (Alfvén 1947) problems: howare they excited? how are they dissipated? how are formed the smalldissipative scales?
Resonance absorption (Ionson 1978) problems: waves withsmall periods needed (5 – 300 sec) [Davila, 1987]
Phase mixing (Heyvaerts & Priest 1983)
Ion cyclotron waves (McKenzie et al. 1995)
Turbulent cascade to small scales problems: (next slide)
2 traditional approchaes AC/DC
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Turbulent cascade to small scales
The couplings between waves and turbulence areuniversal mechanism in fluid forming small scalefluctuations:
Developed turbulence. Energy cascade from large scales to small ones.(Kolmogorov 1941, Frisch 1995):
E(k) ~k -
Conducting fluid. + < B >
But nT and B2 also dissipate after cascade toward smallscales (Iroshnikov et R. Kraichnan),
E(k) ~k -3/2
Natural mechanism to form small scales
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44
Turbulent cascade to small scalesProblems :
1. Energy flux of waves transformed to particle energy:
W diss ~ ( i/ driver) -1 x W total
2. Slow processes (open regions). Distance
Lmin ~ Rsol
3. Time to form turbulent spectrum:
T~ 10 Lmin / Cs
4. Sources are not only in large scales
- Only small part of
Total Energy dissipates
- Spectra forms at very large distance from the Sun
- is too long
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Experimental Evidence of small scale sourcesKrucker & Benz , 1998 (SOHO), Parnell & Jupp, 2000, (TRACE),Koutchmy et al. , 1997(X-ray) etc… – experimental confirmation ofimportant role of nanoevents in coronal heating.
Aschwanden et al. (2000) - quasi-homogeneous spatial distribution ofnano-flares.(SOHO, TRACE)
Shriver et al. 1998, - (quasi-homogeneous spatial distribution ofsmall scale dipoles) (SOHO)
Abramenko et al. 1999 – inverse helicity cascade (Big Bear)
Berghmans et al 1999, Benz et al, intracell nanoflares.
Krasnoselskikh et al, 2002 - The characteristic scale of magnetic loopswhich provide energy deposition into the corona is of the same orderas the dissipation scale.
Observations of magnetic loops of different large scales in EUV
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Dissipation of magnetic energy & small scales
2. Heating by dissipation of DC currents dissipation
• Anomalous resistivity (Handbook of Plasma Physics, edited by M.N. Rozenbluth and R.Z.
Sagdeev, Priest et al, Voitneko et al. )
• Reconnection (Giovanelli,1946)
They both describe the coronal response to perturbation created by sub-photospheric convection(Heyvaerts,1990).
The distinction essentially depends on time scales
tA >> tphotosph AC
tphotosph>> tA DC
DC
Comment: There is no strong difference between AC and DC mechanisms:
Nowadays DC mechanisms are more compatible with coronal observations.
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Chromosphere: spicules and p-modes
Swedish 1-m Solar Telescopewith adaptative optics. Spatialresolution ~100km (0,15")
New result:The spicules are forme at the same point and in phase with oscillation ofphotopsheric p – modes, with the coherent period of 5 min. (De Pontieu et al.2004, Nature, Zhugzda et al. 1987, JETP)
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Ejection +30 km/s
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The prominences: general properties
Big light draperies suspended above thesurface suspendues:
Cold and dense masses of gaz.Mix Structures: Coronal and chromospheric.
Properties:Temperature: 10000 KDensity: 1010 à 1011 cm-3 (500 x coronaldensity)Height: 20 – 100 000 kmWidth: 10 000 kmLenght: up to 1 Rs
, BBSO
TRACE, FeX, 17,1 nm
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The chromosphere: general structure
Observations in H :Eruption phenomena
Filaments et prominences:Situated in the coronaProminences: off-limb.Filaments: on disk
Coronographe, Obs. Pic-Du-Midifiltergram, USET, ROB, Bruxelles
Localisation:Above neutral lines of the
photopsric B:Often E-W orientation.The basis of coronal jets.
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The promineces: quiescentes an eruptives
Quiescentes prominence:Stable structure during days.
Eruptive promineces:Fast ejection ~1 h.
SOHO/EIT, HeII, 30,4 nm
Two evolutionary stage:
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The prominences: eruptions
Eruptions of prominences:Associated to flares in AR, canoccur far from AR.Association to CME.Vielocity: up to 1000 km/sMagnetic energy liberation duringthe eruption.
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The Prominences: formation mechanism
Different configurations are possible with commn points:Magnetic arcade above the neutral line.Horozontal flux trapped in the arcade
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The prominences: strings of twisted fluxes
3D MHD Model:Appearence of twisted strings byapplication of convection velocityfield at the photospheric level.
(Amari, T. et al., ApJ518, 1999; Aly, J.J. & Amari, T. AAp207, 1988, )
The Moving Sun
Quiet atmosphere: Transition region
Thin layer: thickness < 100kmExtreme T gradient gradient: from 2 x104 up to 1 x106 KAbrupt transition betwen chromopshre and corona.
T profile and typical emmissionlines in TR.
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Transition region: structures
Emission in EUV ( <120nm):
Emission lines of stronglyionized atoms.
For increasing T transitiontransition fromchromsopehric structures:
Cgromospheric newtork,spicules, prominences
To coronal structures:Coronal holes, loops.
SOHO/EIT, HeII, 30,4 nmT= 8 x105 K
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Transition region: structures / temperature
SOHO/SUMER, CIV
SOHO/SUMER, SVI
SOHO/EIT, HeII, 30,4 nm, T= 8 x105 K
The Moving Sun
In the high chromosphere and transition region, a transition inthe relation bewteen magnetic pressure in the flux tubesand tehkinetic pressure of the gaz.Coefficient du plasma:
Photosphere and chromosphere: >>1Filed confined in the thin flux tubes in the intragranulas space.Filed frozen in plasma: turbulent convection disturb the filed.
Transition region and Corona: <<1Magnetic filed expands for whole avaliable volume.Plasma is entrained by its movements.
NB: In the solar atmopshere not a lot of regions has 1
Magnetic transition
02 2B
p
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Transition region: topology
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Transition region: global dynamics
"Blinkers":Localized intensity peaks in quietSunLifetime < 10 min>Surface: 100 Mm2
High densitySmall velocity.
Injection of heated chromopshericplasma (« evaporation »).
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Transition region: global dynamics
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Transition region: global dynamics
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IISolar Corona and Heliosphere
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The Corona: General Structure
New structure appearsin the coronal emissions(X-UV)
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Solar Atmopshere: the Corona
Most long part of the SolaratmosphereBefore space era, observedduring eclipcesContinous expansion avec V~400km/s: solar wind.Extension on many AU: theheliosphere with all solar planetsinside.
Very inhomogeneous layer structuredby magnetic field ( <<1)
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Couronne: structures principales
Jets coronaux (équateur, latitudesintermédiaires)Condensations coronales (base des jets,contenant parfois une cavité)Trous coronaux sombres (pôles)Plumes polaires (pôles)Protubérances (chromosphère, H )Grands écarts de densité: jets 10 x trous
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Corona: limb brightenings
SOHO/SUMER Si VI SOHO/SUMER C IV
SOHO/EIT Fe XI
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The Solar Cycle
The Solar activity strongly varies with11 years period as sunspot indexindicates already ~200 years. Thechanges are more visible in the corona.
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The Solar cycle
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The Solar Cycle: magnetic field and X-Ray.
1992 1999
Kitt Peak magnetogramsYohkoh Soft X-ray
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Active Regions dynamic
In the corona, above intensivemagnetic field one can see theActive Regions in the permanentevolution. From times to timesthey produce magnetic fieldinstabilities that lead to solarflares or eruptions.
SOHO/EIT
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The corona: bright points
Small compact structures in the quiestSun and coronal holes. Environ 300 surtoute la surface
Ephemeral AR(small loops)Lifetime: 2h – 2 days.High density
Modele: magnetic submergingdipole.
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The Corona: Coronal Holes
Less dense zones ( factor 4 -10) and less hot (1 x106K) :
No X-Ray emission – hole.Quit region of quietphotopshere.Open B. Plasma escapes.
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Coronal Loops
In the corona,magnetic field linesform loops remplishedby plasma, as one cansee on EIT images.
These loops are inpermanent movement.
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The Coronal Loops
Basic elemnts of quit andactive Corona.
Closed B.Keeping of coronal plasma.
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The Coronal Loops: Dynamics
Strong thermalconductivity thermiquealong B lines.Weak conductivity inperpendicular direction.Isolated loops withindividual evolution.PLAsma transport ispossible only along B:
Macroscopic flows along theloops (v ~ 100 km/s) =intensive currents.
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Coronal loops dynamic
TRACE
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Coronal Loops
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Coronal Loops
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Boucles coronales
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Boucles coronales
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Coronal Loops
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Conclusion: quiet atmosphere
The quiet Sun forms the context where the violent transitory events mayoccur.It affects and modulates the properties of active penomena (Corona andsolar wind).It is formed by similar phenomena by at the small scales, weak energies.Multiple of those micro phenomena create « permannet regime » from tehglobal point of view.
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Flares and CMEs
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Solar Flares: definition
Sudden and temporary heat of the certain volume of solaratmosphere, producing plasma > 107 K and associated to fastreconfiguration of magnetic field.
First observations in 19 century:White light flares – very rare phenomena.
Emissions in:From gamma rays to X – extreme temperatureRadio waves: indication of accelerated particles.
Most energetic solar explosif phenomena in solar :Energy up to 1032- 1033 ergs in ~ 10 – 103 seconds
The Sun is also a power particle accelerator:Electrons: ~100s of electrons 1 MeV:
Electrons of energies ~10-100 keV - 50% of whole energyGeneration of 1036 electrons/s and currents of 1017 Amps.
Ions: ~ 10s of particles 1 GeV :The ions of energies >~1 MeV can transport total energy.
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Solar Flares: Chronologic scenario
Many phases
Precursor:Small energy releaseRadio and soft X Ray
Impulsive phase:Explosive energy injectionMany fast jumps.-rays
Principal long phase:Energy release.Gradual evolutionMaximum and strat of teh coronal andchromospheric (continuum,H ).
Dulk et al. 1985
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Chronology: Pre-eruption phase.
External Generation :Emergence of FluxFlux cancelation.Random walk of footpoinst loops and bydifeferntial rotation.
Slow accumulation and energy storage in the twisted magneticfiled:
Instability trigger after a treshold.
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Solar Flares: classification
Reference measurment, GOES:
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Solar Flares: morphology and et dynamics
16/8/2002, USET, ORB
Mechanism: magnetic reconnectionObserved emmisons come from difeferntlayers.
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Model: Motivations
Energy release associated to solar flares. Powerlaws, flares, microflares. Power index <2 for Parker hypothesis.
System with large fluctuations (high probability)!No thermodynamic equilibrium.
flares similarity at different scales and energy?
what is the respective role of flares of different scales and their interaction in the heating?
Crosby, Aschwanden & Dennis 1993
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Motivations
Some limitations of ‘traditional’ simulations
MHD, Kinetics, PIC simulations may reproduce limited spatio-temporal scalesFor example, ideal MHD does not describe correctly suchdissipative effects as magnetic reconnection or current sheetinstabilities.
But coronal heating is a complex problem, with a lotof different temporal and spatial scales
Traditional approchaes do not work:
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Lattice model (since 1991)
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Part I
Small Scale drivers of different properties
Different mechanisms of current dissipation
Do they influence1. Large scale observable magnetic field
&2. Global Dissipated Energy?
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Magnetic field
sub-diffusive intermittentsource
super-diffusive source
random source
Small-scale sources form magnetic structures:
chaotic source (poor navier-stocks) Reconnection dissipation –
power law deviations
Anomalous Resistivity-Gaussian
Main conclusions. Small-Scale
dissipation mechanisms influence electric currents total dissipated Enregy.
B-Source influences large scale magnetic field structures.
Mechanism of Electric current
dissipations influence PDF
of energy :
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Power Law for Flares WTD
Waiting Time Distribution (WTD) betweenflares is rather robust and easy characteristic
to compare models and experiment
Problems
Experimental WTD are in power laws. WaitingTime Distribution for large set of flares (e. g.Crosby 1993,1996; Weathland 2000)
WTD from models are different. Nowadays allmodels including all known SOC, Shell and Latticemodels (including all our previous studies ) showsPoissonian or exponential laws (e.g. Carbone2000).
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Power Law for Flares WTD
Power Laws: Indicator of long-rangecorrelations Turbulence?
– effect (turbulent dynamo) explains the
origin of solar magnetic field. -effectgenerates structures of larger scales from thesmall ones.
Thus – effect can naturally provide us the“intermediate” and the large scales magneticstructures as magnetic drivers (to avoiddirect cascade problems).
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Intermediate Driving Scales of coronal heating
Inverse cascade by – effect
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Turbulent dynamo: history (1/3)Origin of solar magnetic field by turbulent dynamo (Moffat 1978, Zeldovitch 1983)
effect Parker 1966, Steenbeck et al 1966
The -effect belongs to cinematic dynamos, where the velocity V is imposed.
It is therefore a linear problem, whose goal is to show the large scale growth of an initial “seed” of magneticfield.
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Turbulent dynamo: history (2/3)
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Turbulent dynamo: history(3/3)
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Introduction of -effect in the model
Dynamo: generation of magnetic field by plasmaturbulence. Can be important near the surface. internalsource of magnetic field. Include alpha-effect in theinduction equation:
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Large and intermediate scale sources
Source is random (inital image is white noise).
Currents are dissipated by reconnection, low instability thresholds.
Spatial structure of the magnetic field, taking into account the -effect.
In this run dissipation stabilizes the development of larger structures
Stationary state
t= 100 t =700
Size ~0.3 convection cell
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Dynamics: chromosphere
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Dynamics: chromosphere
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Dynamics: chromosphere
Frequent appearance and eruptionof bright double ribbon and neutralline.
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Waves on the Sun
SOHO/MDI
A flare trigger a Sunquake
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Dynamique: chromosphère
Fast magnetsonic shockpropagation (Moreton wave)Associated to strong flares.
V ~ 1000 km/s
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Dynamics: Corona (Extreme UV)
TRACE: 19,5nm, T=1,5x106K
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Dynamics: Corona (Extreme UV)
Double flare at 15 avril 2001 (sympathetic flares)TRACE: 17,1nm, T=1x106K
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Dynamics: Corona (Extreme UV)
Flare sequence d'éruptions Octber -November 2003SOHO/EIT: 19,5nm, T= 1,5x106K
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Dynamics: Corona (X and Rays)
RHESSI: first images in X and raysPrimary source of heat during impulsive phase.
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Dynamics: Corona (X and Rays)
Thermal emisison in soft X-Ray (<10 keV) presentalong all loop.
Non-Thermal emisison (20 - 50 keV)concentrated in 3 regions :
FootpointsTop
Measurment of time lag bewteen reconnectionsource and X-Ray source.
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Dynamics: post-eruption arcade
Progressive seperation of arcadefootpoints :
V : ~10 km/sIndication of reconnection propagatingmore and more high from the neutral line.
After hs – reformation of filament intoarcade.
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Solar Flares: magnetic reconnection
All models reproducing the topology of flare energy release implyVery small scale of disispationStrong increase of local resisitivity
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Solar Flares: magnetic reconnection
Simplest topology (Sweet 1958, Parker 1963): neutral sheetTypical X- configuration topology :
Elongated: combined effect of Archimede force and solr wind.2D analytical Model.
Strong but unsufficient dissipation.Generation of double plasma flux with Alfven velocity.
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Solar Flares: magnetic reconnection
Petschek Model(1964):Slow shock waves production fromreconenction site.Particle acecleration.Energy converted into heat andacceleration half by half.
Recent Models :+ Turbulence Inclusion de laturbulence+ 3D Topologies(Brown & Priest 2001)
References:Reconenction and shocks models: Kopp &Pneumann 1976, Parker 1979, Priest &Forbes 1986, Priest & Lee 1990.Magnetic energy conversion in thermalandkinetic energy: Syrovatskii 1966, Somov1994
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Solar Flares: unated model.
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EIT waves: definition
Bright front visible in theEUV. It propagates in thesolar corona with thevelocity of 100 km/s fromARs after flare:
Discovered in 1997 bySOHO/EITCan travel trough the wholehemisphere during 1h.
(SOHO/EIT, 12 mai 1997)
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EIT waves: example du 12 mai 1997
SOHO/EITFe XII, 19,5 nm
T ~1.5 MK
Éruption C1.3 flare withfilament eruption andhalo CME.
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Ondes EIT: exemple du 12 mai 1997
Différences entre imagessuccessivesVitesse de propagation:
250 km/s
SOHO/EITBande Fe XII, 19,5 nm
T ~1.5 MK
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EIT waves: dimmings
Double dimmings(tranient coronal holes)
Arcade post-éruptionPlasma evacuationMagnetic lines opening
Association to CME.
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Ondes EIT: déflection (TRACE)
19,5 nm (FeXII) 17,1 nm (FeX) H Ly (121,6 nm)
Images
Différences
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EIT and Moreton waves
Images par différences successives en HaObservatoire solaire de Kanzelhöhe(Pohjolainen et al. 2001)
Moreton waves associated to flaresare observed in the chromopshereLes ondes de MoretonInital velocities: 750 - 1300 km/s>> vc dans la chromosphère.
No possible chromospheric origineDecceléerationPropagation up to 5 x 105km fromeruptive site.
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EIT and Moreton waves
Cospatiality is stilluncertain:
Coincidence only neareruption cite. (Thompson etal. 2000).No correspondence (Eto etal. 2002).
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Trigger by wave front
Coronal shocks (Thompson, 1998)
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Solar Influence Data analysis Center
Flares Catalog
NOAA
Active Region
for each flare
Manual
SEC/NOAA
Flare list, SXI
o Since 01/01/2004 unique spatial information provided bySoft X-ray Imager of GOES satellite. Firstly 84 % of allobserved flares are listed with their coordinates. 11% comesfrom other sources.
EIT Flare
positions
H Flare
positionsOther
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SIDC Flare Catalog
o Since 01/01/2004 SIDC provide correlation between eachflare and NOAA Active Region. This allows statistically valuablestudy of time-distance correlation between distant flares.
o 01/01/2004 – 01/09/2005: 3447 flares(B-X classes), 95 %with coordinates
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Velocity of Perturbation
t1
t1
t2
D1
t3
D2
o We compute the distance alongthe Sun's surface between all pairsof flares separated in time shorterthan tmax=1h,2h, … 20h,assuming that flares separated intime larger than tmax, areuncorrelated.
o We introduce the velocity of the
propagating perturbation as follows:
• This quantity would be meaningful only for flares which are
physically connected, if any.
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129
The first consideration of global inter-flaring spatialproperties.
Velocity [km/s]
PDF of the speed flare-to-flareintercommunication signal
PD
F
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Time-distance coronal seismology ?
4.817 flares measured with their time and position - complete statistical ensemble
Inte
r-fl
are
dist
ance
Inter-flare time
JOINT PDF
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EIT waves: modeles
vEIT ~ 0.34vfast
Formation of 2 wavestructures:
Big wave with floucontour is EITwave(250 km/s)Shock driven by theeffect of « piston »has velocity 770 km/s
Moreton wave
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dimmings
EC
front
dimmings
EC
front
EIT wave front rotation
Podladchkova and Berghmans2005
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ACW rotation
12th May 1997 ACW event
CW rotation
7th April 1997 CW event
Reverse “S” sigmoid
Negative Helicity
Forward “S” Sigmoid
Positive Helicity
Attrill et al 2007
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Amari et al. 2003
CME flux rope eruption
Evolution in two phases:
First a twisted flux rope is created,slow and almost quasi-static;
second a disruption, which isconfined for a small initial helicityand global for a large initial helicity.
Following the evolution of flux ropeAND waves in such geometries iscomputationally difficult.
Kink in itself tendentiallyslow/alfvenic
Extended unfolding wave source,might conceivably explain rotation ofwave front
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C
• The highest point of wavefront (point E) ispercived by both spacecrafts.
• EF: wavefront height
A (STEREO-A)
D
Schematic View of Coronal Wave
B (STEREO-B)E
F
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Cup of Coffee Analogy
High cup borders close from our view the correspondent bottomparts
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CMEs 3D Studies
STEREO - A STEREO - B
Simultanious View
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Improving Resolutionexist at Micro-Scales
EUV Micro-Erptions Extracted Micro Dimmings
Area & Intensity 103 smaller!
comparing to
previously
known events
Micro-Eruptions explain Solar Wind Formation near the Sun
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WHI STEREOWHI STEREO--A DETECTIONSA DETECTIONS30 March Event
of dimming intensity
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WHI STEREOWHI STEREO--B DETECTIONS (3/4)B DETECTIONS (3/4)Event March 30
Violent eventscan be observedin EUV coronaeven during the«quiet» WHIperiod
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WHI STEREOWHI STEREO--B DETECTIONSB DETECTIONSEvent March 25
Event beginsEvent beginsat Eastren limb,at Eastren limb,globallyglobally
propagatespropagatestrough thetrough the
easterneasternHemisphere,Hemisphere,and dissipateand dissipate(or disappear)(or disappear)
near solarnear solarcentercenter
Global events can be observed in EUV corona even during « quiet» WHI period
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Flares
TRACEBig Bear Solar Observatory
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Flares
TRACE
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Radiation storms
SOHO/EIT
A Flare in “suitable place” can émettrein the Earth direction charged particles,that lead in radiation storms. Suchstorms are the danger for satellites andastronauts. On the animation one cansee “the snow” after the flare.
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Coronal Mass ejection
SOHO/EIT
During Flares, big plasma clouds areoften ejected from the Sun,producing Coronal Mass Ejection.
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SOHO/LASCO
Coronal Mass-Ejection (CME)
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Eruptive Prominences
Mauna Loa
SOHO/EIT
The prominences that are big clouds ofplasma cooler than coronal environmentcan also become instable and explode.
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SOHO/EIT
Halo CME after Prominence Eruption
When CME is directed toward theEarth we can see it as the HaloCME. First o all we see theprominence eruption.
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SOHO/LASCO
Halo CME
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SOHO/LASCO
Halo CME
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Solar Activity: CME
Bright structure of plasma ball that propagatesfrom low corona toward heliosphere and caninteract with planet magnetopsheres.Discovered in 1970 by SKYLAB
Most importnat manifestation of solaractivity(together with flares)Principal source of geomagnetic storms.2 aspects of magnetic energy release:
Flares: thermal energy production(heat).CME: production of global macroscopic fluxes(kinetic energy), observed by white light.
02BcH 02BcH
SMM, 14 avril 1980, W. Wagner
Syntheses: Kahler (1987, 1992),Hundhausen (1999), Forbes (2000),Klimchuck (2001), Cargill (2001),Low (2001)
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CMEs: structure in 3 parts
3 composantes imbriquées :Bright front supposing expanding magnetic loop.Dark CavityInterior core: fragments of dense filemanents.
In situ measurments show oftehn 4th invisiblecomposante shock wave before the bright front.
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ICMEs: Sursauts radio
Type II burst (hectometric and kilometric band,20 - 1000 kHz)
Measured only out of terrestrial atmopshere
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CMEs: structure
Some structures(jets) can be destructed by CMEpassage but CMEE keeps its form during whoelpropagation.Strong magnetic conenction to the Sun.Connexion magnétique au Soleil persistante:
Desattached plasmoid never clearly observed.
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ICMEs: magnetic clouds
Ejected Magnetic cloudtransports magnetci field.Caracterised by:
Important and progressiverotation of magnetic field.Proton temperature is low withrespect to ambient plasma.
Dimension at 1UA: ~0,25 AUTransit to the Earth: 1 - 2 days.
Produce negative Bz:Strong tererstrial magnetopshericperturbations.Principales structures thatinfluence Solar-Tererstrialrelations.
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ICME in CIR: corotation interaction regions
Density, T and B increaseCrusial 180° inversion of thedirection of the azimutal filedImportant deviations ofBz(oscillations)Direct and invers shockswaves.
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Heliosphere: CIR
Quand un courant de vent rapide suitun secteur de vent lent, le vent rapiderepousse le vent lent et interagit aveclui.Compression: renforcement de ladensité.Apparition d'une couche d'interfaceturbulente.Formation de chocs:
Zone d'accélération de particules: une dessources des particules solairesénergétiques (SEP: solar energeticparticles).
Régions d'interaction en corotation,RIC (CIR: corotating interactionregion).
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Heliosphere: propagation of ICMEs and CIR
Simulation ofsubsequent CMEs ofOcober 2003).Animation ofinterplanitary magneticfield.
Red: outoming(positive)Bleu: incoming(negative)
Geophysical Institute,University of Alaska,2004
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CMEs: propagation
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CMEs: structure
Different morphologies:Interaction with solar windand B.
Internal complexstructure:
Multiple of loopsObsrevations in tehoptically thin corona –ambiguity.
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CMEs: 18 October - 7 november 2003
Periode of very strong activity in 2 active regions (EIT: Fe XII, 19,5 nm)
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CMEs: 18 october - 7 november 2003
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CMEs: sources and precursors
Eruptive filamentevolution on solar diskEIT (FeXII)6 h later CMEdetected.
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CMEs: dimmings EIT
Dark regions after EIT wavestriggered by flares: :
Eruption mode: opening of magneticfield lines.
Assymetry in preexicted magneticstructre.
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CMEs: EIT dimmings
Diffeernce with initial imageShows dimmings
Progressive difference:Show EIT wave
Flows, 30 km/s (SOHO/CDS, Harra & Sterling 2001)
Disispation during expansion.NEMO
SOHO/EIT:12/5/1997,
19,5nm
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Waves on the Sun
SOHO/EIT
In these images obtained bysubstraction of the previousone, one can better follow thegigantesque shock wave aftera flare.
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CMEs: velocitis and acceleration
2 classes of CMEs (Sheeley et al. 1999):Gradual CME :
Formed by the prominence and their cavities.Progressive Acceleration below 30 Rs
Impulsive CME:Triggerred by the Flares.Associated to EIT waves.High velocity, constante or with deceleration.
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CMEs: latitude distribution
Minimum (1996) Maximum (1999)
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CMEs HALO
The most importnat class for solartererstrial relation.
Shocks source, SEP and geomagneticperturbations.
Frequency (sur base des fréquences globales et desdistribution en latitude et en largeur):
~ 15% of all CMEs
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CMEs halo
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CMEs halo
Progressive differences
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CMEs: modeles
Basic elements to reproduce: the observations imply the shearing/torsionof magnetic field applyed along the neutral line on the photopsheric level,« carrying wrapping instability » (kink instability).2 types of models:
Analytical models:Quantittaive information about physical mechanisms.Difficult to reproduce observed morphology.
Numerical Modles :Better reproduction of observations.Initial conditions must be known with high pression.Models in 2 parts:
Fine grid for for the Corona (trigger)The Grid less dense for reproduction of propagation in the heliosphere.
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CMEs: sources and precursors
Ejected filament is often twisted – helicityEnergy storage in teh helicity.Unrolling of magnetic line during the propagation. (magnetic energy release).
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CMEs: precursors and helicity
LASCO C2, 2/6/1998, 13h31
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CMEs: precursors and helicity
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CMEs: modeles
5 categories of modeles:1. Thermal deflagration2. Dynamo3. Mass loading4. Rupture of connections ("tether release")5. To put under the tension of connections ("
tether straining")Syntheses of modellng: Low (2001), Wu et al.(2001).
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CMEs: modèles
Lin et al.2004
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LASCO as the Comet hunter
SOHO/LASCO
With the help of LASCO athousand of new cometsare discovered nowadays.
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Solar Wind: the first indiexes
First observations suggested the expandingmedium in the solar system 19th century:
Carrington (1879): correlation between whit elightflare and magnetic field measuremnt 2 days later..Comet observation: gaz and dust tails always in outSun direction (Biermann 1951).
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Solar wind: Velocity Profile
Asymptotique velocity at longdistance as the function of tehtemperatur ein teh low corona :
200km/s at T= 0,5 x106 K400 km/s at T= 1 x106 K650 km/s at T= 2 x106 K
It strats at 3 Rs (LASCO) Sheeley et al. 1998
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Solar wind: acceleration
Different for slow wind (plasma confined in the closed field):Continous emergence continue of magnetic flux and opening byreconenction on teh top of the large scale loops.
Heating and acceleration of tehfast solar wind by MHD wavesby the mechanism of the ion-cyclotron resonance.
The Moving Sun
Solar wind: the source localization
SOHO/SUMER: observation –doppler shift in NeVIII (77,0 nm,T= 650 000K) (cf. Hassler et al.1997, 1999)
Flux up l'extérieur (décalage versla bleu shift ) dominating in thecoronal holes.
Maximum flux – on the trace ofthe border of the chromosphericnetwork
Correspondance with theunderlying magnetic fieldstructure.
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SECCHI suite
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HI-1 CME
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HI-1 CME-Venus
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ICME at the Earth
When CME achieve theEarth, it perturbs theterrestrial magneticfield.
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Polar Aurora
The CME impact on the Earthtrigger very often a geomagneticstorm, that can cause the polaraurora.
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Aurores
Au passage d'un CME, injection renforcée d'énergie et de particulesdans la magnétoqueue.
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Impacts sur l’environnement terrestre
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ENDENDThat was only a flyover of the Sun,That was only a flyover of the Sun,
an exciting star in direct contact with ouran exciting star in direct contact with ourenvironmentenvironment
andand
One of the central research objective for the comingOne of the central research objective for the comingyearsyears
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Solar Space projects in near future
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SDO: AIA
Central satellite of NASa program"Living with a Star"Launch: 2008-95 - 10 ansOrbite: geosynchronous
(TB/day)
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SDO: AIA
3 instrumentsHMI: helioseismology, vector magnetographEVE: spectro-photometre UV-EUVAIA: telescope EUV 7 wavelength
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Solar Orbiter / EUI: Extreme UV Imager
Mission:Launch: 20135 - 7 ans
Orbit:Distance to Sun: 0,21 AU (32 millions km, 45Rs)Partially heliosynchronousInclinaison: 30°
Spatial resolution : 200 km