Status on SSI and Mg II from GOME/SCIAMACHY/GOME-2 IUP Bremen contribution to the SOLID project Mark Weber, Wissam Chehade, Asher Riaz Universität Bremen EU SOLID Annual Meeting, Orleans, France, Oct. 2013

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

SCIAMACHY/GOME/GOME-2 SSI GOME: SCIAMACHY: GOME-2A: 2007-present GOME-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: nm (GOMEs nm) Spectral resolution: – ~1.5 >1000nm – < 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: nm Ch. 7: μm

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 ( nm)  Updated datasets for EU SOLID

Some controversy: 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

Some controversy: NIR SSI Models (COSI, SRPM) are between ATLAS-3/SIM and SCIA/SOLAR Solar1/WHI adjusted to ATLAS-3 SCIAMACHY spectrum from the beginning of the mission (2002)/ WLS corrected Thuillier et al., Sol. Phys., accepted  see talk by Thuillier

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 [mW/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 for creating 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 >> 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): 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 talk by Chehade – Update/improve IUP data products (Task 2.1) Mg II index Ca II/Mg I index 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)

Appendix

SSI database (discussion) Structure of database – data storage which data to store – ‚reference‘ SSI data (‚single spectra‘, e.g. Hall & Anderson, Kurucz, Nickel & Labs, Shuttle-Atlas‘, rocket data, Wehrli composite) – SSI timeseries (SBUVs, UARS, ENVISAT, SOHO,…) – proxy timeseries (F10.7, Lya, MgII, CaII, PSI, sunpsots,….) – New datasets from/during this project – primary literature to the data (pdf‘s) Wavelength range of SSI, e.g. > 115 nm, EUV: nm – Split responsibility: EUV: ROB, UV/VIS/NIR: UBre common file format web interface to data/visualisation? digitalisation of data? – Web page (how to present the database/documentation/quality assessment) – Links to other databases (e.g. LASP LISIRD) – Property rights? restricted to the consortium initially – Updates (‚living database‘) – public outreach

UV wavelength definitions ISO standard (ISO-21348): ISO standard

27 day signature in SCIAMACHY stratospheric ozone – different frequency analyses of ozone CWT, FFT, cross-correlation – max. cross-correlation during SC is 0.38, weaker than in prior solar cycles (see also Fioletov, 2009) – 27d signal in ozone is varying and vanishes for selected 3-month periods (max correlation r=0.7) about a factor 2 smaller than observed in other studies and earlier solar cycles (e.g. Gruzdev et al., 2009) blue: ozone black: Mg II index Dikty et al. 2010b

SCIA Proxy Model SCIAMACHY proxy model – allows reconstruction of solar cycle change in SSI – assume that magnetic surface activity are responsible for irradiance variations (Fligge et al., 2000) – assume that solar rotation changes scale up to solar cycle scale – Parameterization of SCIAMACHY SSI changes in terms of scaled solar proxies, here Mg II index (faculae brightening) and photometric sunspot index PSI (sunspot darlening) – similar approach: Lean et al., 1997, 2000 SCIAMACHY SSI at a reference date Mg II indexPSI index piecewise polynomials (degradation, anomaly corrections) Scaling parameters derived from several solar rotations Mg II index PSI index Pagaran et al., 2009

SSI solar cycle changes – Comparisons of SSI changes during descending phases of SC SCIA proxy model (Pagaran et al., 2009,2011b) NRLSSI model (Lean 2000) SATIRE model (Krivova et al. 2009) Deland & Cebula UV composite SIM/SORCE and SUSIM observations – SIM changes during SC 23 four times larger than the models and doubled the changes of SUSIM and UV composite during SC 22 challenges the validity of models assuming solar surface magnetic activity as a primary source of SSI changes large impact on atmospheric heating rates (Calahan et al. 2010, Haigh et al. 2010) and mesospheric ozone (Merkel et al., 2011) Pagaran et al., 2011b 2004/01 minus 2007/01 (not a full solar cycle) Ermolli et al., 2012

Mg II and Ca II emission x – Ca II emission core not spectrally resolved – Does Ca II provide additional information (not already contained in MgII)?

SSI timeseries from space Request for SOLID partners: Provide a list of SSI and/or proxy data he/she has access to by contacting useful information: link to data or size of data file(s), data format, primary reference to data (PDF) Will send out questionnaire for data and provide ftp server for data dumping Ermolli et al., 2012

List of SSI missions (>115 nm) European missions