Status on SSI and Mg II from

GOME/SCIAMACHY/GOME-2

IUP Bremen contribution tothe SOLID project

Mark Weber, Wissam Chehade, Asher RiazUniversität Bremen

(Mark.Weber@Uni-Bremen.de)

EU SOLID Annual Meeting, Orleans, France, 14-17 Oct. 2013

Content

• SSI from SCIAMACHY/GOME/GOME-2• recent work on the Mg II index• Outlook on future work (e.g. EU SOLID)• SOLID database

SCIAMACHY/GOME/GOME-2 SSI

GOME: 1995-2011SCIAMACHY: 2002-2012GOME-2A: 2007-presentGOME-2B: 2012-present

– Daily full solar disc measurements using a diffuser

– Radiometrically calibrated before launch

– Challenges:

• instrument and platform anomalies

• UV radiation damage (deposits of comtaminants on optical surfaces)Pagaran et al., 2011a

SCIAMACHY

GOME/GOME-2

GOME/-2

Solar irradiance measurements by SCIAMACHY• Continuous coverage: 230-1700

nm (GOMEs 230-800 nm)

• Spectral resolution: – ~1.5 nm @ >1000nm– 0.2- 0.4 nm @ < 1000 nm

• Spectrometer design: double monochromator (predisperser prism and gratings in each channel)

• Reticon linear diode array detector

Pagaran et al., 2011a

GOME/GOME-2

SCIAMACHY optical throughput monitoring

• SCIA: UV optical degradation weaker than GOME/GOME-2

• Icing of NIR detectors /decontamination by detector heating

Ch. 2: 300-400 nm

Ch. 7: 1.94-2.04μm

New degradation correction for SCIAMACHY

• From measurements using various solar light and WLS paths in SCIAMACHY and an optical throughput model layer thicknesses of decontaminants on mirror/diffuser surfaces are fitted– ASM mirror– ESM mirror– ESM diffuser– WLS internal mirror

• takes into account scan angle dependence

White Light Source

Future plans on solar research (beyond SOLID)

Project SCIASOL as part of the BMBF Priority Programme ROMIC (‘Role of the Middle Atmosphere in Climate’)

• Degradation correction to SCIAMACHY SSI (improve optical throughput model accounting for natural SSI variability)

• Recalibrated SSI datasets from GOME/SCIAMACHY/GOME-2 (240-800nm)

Updated datasets for EU SOLID

• NOTE: GOME, SCIAMACHY, GOME-2 data in the SOLID database are still uncorrected data!

Some hot topics: NIR SSI

Bolsee et al., Sol. Phys., revised (under review) See talk by Bolsee

• NIR SSI lower by 8% (>1600 nm) w.r.t.

ATLAS-3/SIM

Mg II index from SCIAMACHY/GOME/GOME-2

• Mg II core-to-wing ratio near 280 nm– Indicator for chromospheric

activity– Correlates well with UV and

EUV SSI changes (Deland and Cebula 1993, Viereck et al., 2001)

– insensitive to instrumental degradation (to first order) (Heath & Schlesinger 1986)

– composites available from multiple sensors (since 1978)

– used for UV SSI reconstruction and degradation corrections

Wavelength (nm)

F [m

W/m

2 nm

]

GOME

solar max & min

GOME/SCIAMACHY/GOME-2 MgII time series

• Classical definition (H&S 1986): GOME-2

• High resolution definition (emission core resoved): GOME/SCIA

Mg II index timeseries database

• Data included in the composite

Matching of Mg II indices forcreating composites

• Scaling by linear regressions in overlapping time periods: – x vs y and y vs x (red) and then

taking averages (blue)• Scaling works best if large overlaps

exists (e.g. GOME-U/SOLSTICE)• However: GOME quite noisy towards

end of its lifetime

Corrections for inhomogeneities• SCIAMACHY(2009/01)

and GOME-2A (2009/09) affected by decontamination activities (detector heating for additional outgassing)

• Composite index:– use N16/SBUV2 as

transfer standard across solar minimum

– Treat both GOME-2 and SCIA as separate time series before and after decontamination when scaling

Updated composite Mg II index

• Unusually low activity in SC 24

• SC24 solar minimum lower than before?

• GOME/SCIA/GOME-2 Mg II indices and composite updated daily

www.iup.uni-bremen.de/gome >> Solar Activity

Comparison to the new SORCE Mg II index

• Very good agreement with N16 and SOLSTICE B• Drift in Solstice A (a solar aperture problem)• Solar minimum of SC24 well covered by current Mg II indices,

some differences after 2011 (aging problems?, needs to be looked upon again)

Snow et al., J. Space Weather Space Clim., submitted

Long-term stability of Mg II index from a single instrument

• Error calculation (very crude):

275-285 nm

Validation of error estimate (GOME-2)

• Qualitative good agreement

• Simple error model needs:– SNR near 280 nm from

preflight conditions– degradation rates

(intensity ratios with respect to mission start)

Long-term stability of GOME?

• Since we roughly average 4 irradiance values (e.g. wing values), we assume ΔW≈ΔI/√4 1/SNR=0.0007/4• Due to advanced

degradation larger uncertainties at SC24 minimum (2009)• NOTE: error only

accounts for random errors!

IUP-UBR contribution to SOLID

• main contribution to WP2 (irradiance data exploitation) – Collecting/updating SSI and proxy data SOLID database (Task 2.1)

see next slides

– Update/improve IUP data products (Task 2.1)

• Mg II index

• Ca II/Mg I/H_alpha,beta,gamma(?),…

• Recalibrated GOME/SCIAMACHY/GOME-2A/GOME-2B

– assessment of SSI & proxy data error analysis incl. long-term stability (Task 2.2)

– composite SSI & proxy data (mainly UV) merging, gap filling, and error analyis (Task 2.5) see talk by Scholl

– Recommendations on 1) exisiting SSI data and 2) future SSI missions (Task 2.6)

SOLID SSI & Proxy database

Working space database• http://www.iup.uni-bremen.de/~weber/ssi_database/– Original data: ascii, binary, …– “Password protected“– user name: ssi_database– password: EUsolid2013

Public data website:• http://projects.pmodwrc.ch/solid/index.php/main-database– common data format: netcdf w/ CF convention– additonal data, e.g. image masks– plotting capabilities

SSI database structure

Data

Proxiese.g. Mg II, Ly-α,

radio fluxes

reference SSI data e.g. ATLAS-3

SSI time series

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