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Element Abundance Results from Element Abundance Results from CDSCDS

Dr Peter YoungDr Peter YoungSOHO/CDS Project ScientistSOHO/CDS Project Scientist

CCLRC Rutherford Appleton LaboratoryCCLRC Rutherford Appleton Laboratory

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Why are abundances interesting?Why are abundances interesting?

• Fractionation found to occur in corona and solar windFractionation found to occur in corona and solar wind– related to FIP of elementrelated to FIP of element– magnitude depends on type of solar featuremagnitude depends on type of solar feature

• Stellar X-ray spectra have revealed an inverse FIP effect in Stellar X-ray spectra have revealed an inverse FIP effect in active starsactive stars

• Photospheric abundances have been revised recently leading Photospheric abundances have been revised recently leading to problems for standard solar modelto problems for standard solar model

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The FIP effectThe FIP effect

• FIP - “First Ionization Potential”FIP - “First Ionization Potential”• Low-FIP (≤ 10 eV) elements enhanced relative to high-FIP Low-FIP (≤ 10 eV) elements enhanced relative to high-FIP

elements in corona and solar windelements in corona and solar wind• Factor varies relative to solar feature, e.g.,Factor varies relative to solar feature, e.g.,

– fast solar wind: 2fast solar wind: 2– slow solar wind: 4-5slow solar wind: 4-5– coronal structures: up to 10-15coronal structures: up to 10-15

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Abundances with CDSAbundances with CDS

• NIS covers two wide wavelength bands covering consecutive NIS covers two wide wavelength bands covering consecutive ion stages for several elementsion stages for several elements

ElementElement FIP/eVFIP/eV StagesStages Log Log TT range range

OxygenOxygen 13.613.6 II-VII-V 4.5-5.44.5-5.4

NeonNeon 21.621.6 IV-VIIIV-VII 5.2-5.75.2-5.7

MagnesiumMagnesium 7.67.6 V-XV-X 5.4-6.15.4-6.1

SiliconSilicon 8.28.2 VIII-XIIVIII-XII 5.9-6.35.9-6.3

IronIron 7.97.9 X-XVIX-XVI 6.0-6.46.0-6.4

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Abundance MethodsAbundance Methods

• Simple methodSimple method– find two ions formed at the same temperaturefind two ions formed at the same temperature– intensity ratio proportional to abundance ratiointensity ratio proportional to abundance ratio

• Complicated methodComplicated method– use line intensities from many ions to create DEMuse line intensities from many ions to create DEM– abundances varied to ‘improve’ fitabundances varied to ‘improve’ fit

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Mg/Ne Abundance in Quiet SunMg/Ne Abundance in Quiet Sun

• Measurements of the FIP effect in the quiet Sun were difficult Measurements of the FIP effect in the quiet Sun were difficult with previous instrumentation (with previous instrumentation (SkylabSkylab) and SUMER) and SUMER

• Isolated measurements using CDS performed by Del Zanna, Isolated measurements using CDS performed by Del Zanna, Landi, MacPherson, YoungLandi, MacPherson, Young– suggest FIP enhancement of 1 – 2suggest FIP enhancement of 1 – 2

• AIM: perform definitive measurements of Mg/Ne ratio in quiet AIM: perform definitive measurements of Mg/Ne ratio in quiet Sun regions over a 2 year periodSun regions over a 2 year period

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CDS observationsCDS observations

• Quiet Sun spectral atlas (NISAT) every week of missionQuiet Sun spectral atlas (NISAT) every week of mission• 2020” x 240” spatial area” x 240” spatial area• Only consider regions away from bright points and ARsOnly consider regions away from bright points and ARs• Data from 1996 March to 1998 JuneData from 1996 March to 1998 June

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Analysis procedureAnalysis procedure

• Complete NIS spectra for supergranule cell centre and network Complete NIS spectra for supergranule cell centre and network regions extracted based on O V imageregions extracted based on O V image

• Emission lines of Ne IV-VII and Mg V-VIII identified and fit with Emission lines of Ne IV-VII and Mg V-VIII identified and fit with Gaussian profilesGaussian profiles

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Analysis procedureAnalysis procedure

• Minimization procedure applied by specifying plasma column Minimization procedure applied by specifying plasma column depths, depths, dd, over log , over log TT = [5.0,6.1], 0.1 intervals = [5.0,6.1], 0.1 intervals

• dd11, , dd22,, dd33 values at log values at log TT = 5.0, 5.6, 6.1 = 5.0, 5.6, 6.1

• Other values obtained by linear interpolationOther values obtained by linear interpolation• CHIANTI/v4.2 used to compute line emissivitiesCHIANTI/v4.2 used to compute line emissivities

• Ab(Mg)/Ab(Ne), Ab(Mg)/Ab(Ne), dd11, , dd22,, dd33 are the 4 free parameters are the 4 free parameters

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Abundance resultsAbundance results

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Abundance resultsAbundance results

• Average enhancements over photospheric Mg/Ne value:Average enhancements over photospheric Mg/Ne value:– Network: 1.25 Network: 1.25 ± 0.10± 0.10– Cell centres: 1.66 Cell centres: 1.66 ± 0.23± 0.23

• Cell centres clearly show stronger enhancementCell centres clearly show stronger enhancement

• More details see Young (2005, A&A, 439, 361)More details see Young (2005, A&A, 439, 361)

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InterpretationInterpretation

• Results consistent with cartoon of H. Peter (2001)Results consistent with cartoon of H. Peter (2001)• Small fraction of quiet Sun connects to solar windSmall fraction of quiet Sun connects to solar wind• Closed quiet Sun loops show photospheric abundancesClosed quiet Sun loops show photospheric abundances

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Active regionsActive regions

• A striking feature of ARs are bright points with strongly A striking feature of ARs are bright points with strongly enhanced transition region linesenhanced transition region lines

• One class of such brightenings have very strong Mg linesOne class of such brightenings have very strong Mg lines

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Emerging AR, June 1996Emerging AR, June 1996

AR 7968

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Emerging AR, June 1996Emerging AR, June 1996

• Inner brightenings in region of flux emergenceInner brightenings in region of flux emergence• Outer brightenings at base of large coronal loopsOuter brightenings at base of large coronal loops

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ConclusionsConclusions

• Central brightenings show photospheric Mg/Ne ratioCentral brightenings show photospheric Mg/Ne ratio• Loop footpoints show Loop footpoints show factor 10factor 10 enhancement in Mg/Ne enhancement in Mg/Ne

• More details see Young & Mason (1997, Sol. Phys., 175, 523)More details see Young & Mason (1997, Sol. Phys., 175, 523)

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Future WorkFuture Work

• General Mg/Ne results for ARsGeneral Mg/Ne results for ARs• Ne/O abundanceNe/O abundance• Minor elements: Ar, K, CaMinor elements: Ar, K, Ca

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General Mg/Ne results for ARsGeneral Mg/Ne results for ARs

• Widing & Feldman (2001, ApJ) found magnitude of FIP effect Widing & Feldman (2001, ApJ) found magnitude of FIP effect related to age of active region using related to age of active region using SkylabSkylab data data

• With CDS it should be possible to look at variation in individual With CDS it should be possible to look at variation in individual AR structuresAR structures

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General Mg/Ne results for ARsGeneral Mg/Ne results for ARs

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Ne/O relative abundanceNe/O relative abundance

• Recent downward revisions of C, N, O & Ne abundances have Recent downward revisions of C, N, O & Ne abundances have caused problems for standard solar modelcaused problems for standard solar model

• Drake & Testa (2005, Nature) suggested solar Ne/O ratio is in Drake & Testa (2005, Nature) suggested solar Ne/O ratio is in errorerror

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Ne/O relative abundanceNe/O relative abundance

• Including oxygen in the quiet Sun Mg/Ne analysis:Including oxygen in the quiet Sun Mg/Ne analysis:

photospheric

Drake & Testa

QS network

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Minor Elements: K, Ar, CaMinor Elements: K, Ar, Ca

• PotassiumPotassium– K VIII K VIII λλ519.4, K IX 519.4, K IX λλ621.4621.4

• ArgonArgon– Ar VII Ar VII λλ585.8585.8

• CalciumCalcium– Ca VII Ca VII λλ551.4, Ca VIII 551.4, Ca VIII λλ596.9, Ca X 596.9, Ca X λλ557.7557.7

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Future MissionsFuture Missions

• Solar-B/EISSolar-B/EIS– ideal for coronal abundancesideal for coronal abundances– Fe/S, Ar/CaFe/S, Ar/Ca

• Solar OrbiterSolar Orbiter– high spatial resolution for studying individual structureshigh spatial resolution for studying individual structures– Ne/Ca?Ne/Ca?