Introduction to the EIS instrument on Hinode

Dr Peter Young, Rutherford Appleton LaboratoryDr Peter Young, Rutherford Appleton LaboratoryHin

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Hinode Data Analysis Workshop, Paris, Nov 2007Hinode Data Analysis Workshop, Paris, Nov 2007

Introduction to the EIS instrument on Introduction to the EIS instrument on HinodeHinode

Dr Peter YoungDr Peter YoungRutherford Appleton Laboratory, UKRutherford Appleton Laboratory, UK


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Basic factsBasic facts

• EIS – EUV Imaging SpectrometerEIS – EUV Imaging Spectrometer• Successor to CDS on SOHOSuccessor to CDS on SOHO• Covers two wavelength bands: 170-211 Covers two wavelength bands: 170-211 Å, 246-292 ÅÅ, 246-292 Å• Principally for coronal spectroscopyPrincipally for coronal spectroscopy

• PI institutes: MSSL (UK), NRL (USA), NAOJ (Japan)PI institutes: MSSL (UK), NRL (USA), NAOJ (Japan)• PI: Prof Louise Harra (MSSL)PI: Prof Louise Harra (MSSL)


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Instrument layoutInstrument layout

Single mirror for focussing – improves throughput of telescope

Multilayer coating – gives high reflectivity in EUV

Back-thinned CCDs – directly sensitive to EUV radiation

Aluminium filters – block out visible light


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Field of viewField of view

E

EIS (576”x512”)

XRT(2048”x2048”)

W

SOT:NFI/SP(328”x164”)SOT: BFI

(205”x102”)

N

A coarse offset can A coarse offset can also be applied to also be applied to offset EIS from the offset EIS from the other instrumentsother instruments


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CCD imageCCD image

CCD-BShort wavelength170-211 Å

CCD-ALong wavelength246-292 Å

2048 pixels

1024

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els


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Slit optionsSlit options

• Four slits available, defined by their widthFour slits available, defined by their width• 1” and 2” slits are for spectroscopy1” and 2” slits are for spectroscopy• 40” and 266” slits for imaging40” and 266” slits for imaging

1”

266”


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Using wide slits: context imagesUsing wide slits: context images

Context slot raster, Fe XII 195Duration: 3min 20s

2” slit raster, Fe XII 195Duration: 22min


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Using wide slits: moviesUsing wide slits: movies

• The most ‘clean’ emission line for the 266” slit is Fe XV 284.16 (2 The most ‘clean’ emission line for the 266” slit is Fe XV 284.16 (2 million K)million K)

EIS wide slot movieFe XV 284.2 (logT=6.3)Courtesy H. Warren (NRL)


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The EIS spectrumThe EIS spectrum

• Spectrum dominated Spectrum dominated by coronal ions (iron, by coronal ions (iron, particularly)particularly)

• Few useful transition Few useful transition region lines, but not region lines, but not strongstrong

Young et al. (2007, PASJ, in press)


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Telemetry limitationsTelemetry limitations

• The EIS data rate is limited to around 50 kbits/sThe EIS data rate is limited to around 50 kbits/s• Data are routinely compressed using DPCM (lossless) by a factor of Data are routinely compressed using DPCM (lossless) by a factor of

around 3around 3– JPEG (lossy) compression is also allowedJPEG (lossy) compression is also allowed

• Despite this, complete CCD data can not be obtained routinelyDespite this, complete CCD data can not be obtained routinely– Specific wavelengths (emission lines) must be chosenSpecific wavelengths (emission lines) must be chosen– reduced spatial coverage along slit (solar-Y)reduced spatial coverage along slit (solar-Y)


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Science capabilityScience capability

• Transition region linesTransition region lines• Coronal iron linesCoronal iron lines• Flare linesFlare lines• Density diagnosticsDensity diagnostics• Line width and velocity mapsLine width and velocity maps


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Transition region linesTransition region lines

• EIS spectra are dominated by coronal iron lines, but there are a EIS spectra are dominated by coronal iron lines, but there are a number of useful transition region linesnumber of useful transition region lines

Density in loop footpointsDensity in loop footpoints

Young et al. (2007, PASJ)Young et al. (2007, PASJ)


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Coronal iron linesCoronal iron lines


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Flaring loop (17 Dec)Flaring loop (17 Dec)


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SpectroscopySpectroscopy

• Emission line diagnostics come in two typesEmission line diagnostics come in two types

• Study of shape and position of emission linesStudy of shape and position of emission lines– yields plasma velocity, broadening parametersyields plasma velocity, broadening parameters

• Study of emission line strengthsStudy of emission line strengths– yields temperatures, densities, abundances, emission measureyields temperatures, densities, abundances, emission measure– requires detailed atomic datarequires detailed atomic data


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Doppler shiftsDoppler shifts

• Each emission line has a standard position (the Each emission line has a standard position (the rest wavelengthrest wavelength))• Shifts from this position imply motion of the plasmaShifts from this position imply motion of the plasma

– blueshiftsblueshifts: towards the observer: towards the observer– redshiftsredshifts: away from the observer: away from the observer

Blueshift Redshift


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Line width diagnosticsLine width diagnostics

• The width of emission lines can be written in velocity units as The width of emission lines can be written in velocity units as

• The components of The components of ΔΔvv are written as are written as

• where where

– ΔΔvvII is the instrumental width is the instrumental width

– 22kT/MkT/M is the thermal width is the thermal width– ξξ is the non-thermal velocity is the non-thermal velocity

22I

2 2 M

kTvv

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Line width and velocity mapsLine width and velocity maps

• Active region mapActive region map– Fe XII 195.12 Fe XII 195.12 ÅÅ– 2006 Dec 22006 Dec 2

Intensity

Velocity

Width


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Close-up of loop: line widthClose-up of loop: line width


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Close-up of loop: velocityClose-up of loop: velocity


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Caution: non-Gaussian profilesCaution: non-Gaussian profiles

• Line profiles are not always GaussianLine profiles are not always Gaussian


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Density diagnosticsDensity diagnostics

• Certain emission lines from particular ions have ratios that are Certain emission lines from particular ions have ratios that are sensitive to the plasma densitysensitive to the plasma density

• EIS is the first solar UV instrument to EIS is the first solar UV instrument to routinelyroutinely allow high precision allow high precision density measurements density measurements – high effective areahigh effective area– access to best coronal density diagnosticsaccess to best coronal density diagnostics


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Density mapsDensity maps

• The high quality of the EIS data make density maps easy to generateThe high quality of the EIS data make density maps easy to generate• Big improvement over SOHO/CDS density mapsBig improvement over SOHO/CDS density maps

Density map from SOHO/CDS

(Tripathi et al. 2006)


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Best density diagnosticsBest density diagnostics

IonIon RatiosRatios

Fe XIIFe XII

(logT=6.1)(logT=6.1)λλ186.88 / 186.88 / λλ195.12195.12

λ196λ196.64 / .64 / λλ195.12195.12

Fe XIIIFe XIII

(logT=6.2)(logT=6.2)λ196λ196.54 / .54 / λλ202.04202.04

λ203λ203.82 / .82 / λλ202.04202.04


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Instrumental effects to be wary ofInstrumental effects to be wary of

• There is a spatial offset in both X and Y between the two EIS CCDsThere is a spatial offset in both X and Y between the two EIS CCDs– X: 2 pixels, Y: 15-20 pixelsX: 2 pixels, Y: 15-20 pixels

• The line centroids vary by around 60-70 km sThe line centroids vary by around 60-70 km s-1-1 through an orbit through an orbit• Line centroids and widths vary along the EIS slitLine centroids and widths vary along the EIS slit• The EIS slits are slightly tilted relative to CCDThe EIS slits are slightly tilted relative to CCD• There are a number of warm and hot pixels on the detectorThere are a number of warm and hot pixels on the detector• There are a few dust particles on the CCDsThere are a few dust particles on the CCDs

– affects Fe XI 188.23 and Fe XII 193.51affects Fe XI 188.23 and Fe XII 193.51• Image wobble (satellite & instrument) leads to strange effect in raster Image wobble (satellite & instrument) leads to strange effect in raster

moviesmovies


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EIS observationsEIS observations

• Basic observation units for EIS are called Basic observation units for EIS are called studiesstudies• Different studies have unique acronyms; there are over 220Different studies have unique acronyms; there are over 220

– e.g., COMSCI_AR3, PRY_footpoints_v2, SYNOP001e.g., COMSCI_AR3, PRY_footpoints_v2, SYNOP001

• Studies actually comprise one or more Studies actually comprise one or more rastersrasters• A raster can be, e.g.,A raster can be, e.g.,

– a scan of a region with the narrow slita scan of a region with the narrow slit– sit-and-stare with narrow slit or wide slitsit-and-stare with narrow slit or wide slit

Documents

Introduction to the EIS instrument on Hinode