Photometric Observations of Solar Irradiance Variability from SFO

1. Gary Chapman, Angie Cookson and Dora Preminger San Fernando Observatory (SFO) California State University, Northridge (CSUN) Photometric Observationsof Solar Irradiance Variabilityfrom SFO

2. According to the “Master Plan” for the California State University (the CSU) there is no direct allocation of time for faculty research (unless one has a research grant) it does not allow the granting of Ph. D. degrees at any State University About CSUN

3. Data Description • CFDT=Cartesian Full-Disk Telescope • Daily observations (digital images) continue using CFDT1 (since 1986) and CFDT2 (since 1992). • Observations obtained on about 60% of days. • Fully processed images available on the Web (). • Photometric indices available on request.

4. Data Description, Cont'd. • Basic Observing Technique • Linear photodiode array is oriented N-S • Image is scanned using Earth's rotation • Sky transparency is recorded every line • Original idea from Gordon Hurford passed on by Hugh Hudson at WARTS workshop(SP-310)

8. CFDT1 Size: 512 x 512 pixels Scale: 5.12 arc-sec/pix CFDT2 Size: 1024 x 1024 pixels Scale: 2.5 arc-sec/pix Image Size & Scale

9. CFDT2 672.3 (10) nm 472.3 (10) nm 393.4 (1.0) nm 393.4 (0.3) nm 780.0 (10) nm 997.0 (10) nm Wavelengths & (BPs) • CFDT1 • 672.3 (10) nm • 472.3 (10) nm • 393.4 (1.0) nm

13. Scientific Justification • Need to understand and remove solar changes from other forms of climate forcing. • Spacecraft measurements of TSI and SSI not imaged. • Our program measures relative changes due to solar activity. • Our photometric indices correlate with TSI with R2 as high as 0.95.

14. Photometric Indices • Red Images • Photometric Sum [uses ALL pixels] • Σr = ∑i (ΔI/I) Φr(μ) [no feature identification] • Photometric Sunspot Index (model) • PSI = CS ∑AS (3 μ + 2) [≤ -8.5%, only] • K-line Images • Σk = ∑i (∆I/I) Φk(μ) [no feature identification] • PFI = Cp ∑Af (3μ + 2)(1/μ – a) [≥ 4.8%, only] Σ

16. REGRESSION RESULTS • S = S0 + A * Σr + B * ΣK • S0 = 1360.81 ± 0.004 W/m2 • A = 1.025 ± 0.008 • B = 0.1257 ± 0.001 • R2 = 0.9495 • N = 1253

17. Scientific Just. (cont'd) • Our data can be used to correct S/C upsets. • Our data can be used to connect different S/C TSI (having different scale factors). • Imaged data necessary to understand the sources of TSI and SSI variations.

20. The Bolometric Contrast, α, is the bolometric irradiance deficit of a sunspot as seen from the surface of the Sun, not from the Earth. A similar term for faculae/ network is not so easy; the facular contrast is a sensitive function of disk position. Bolometric Contrast

21. Bolometric Contrast, con't. • The bolometric contrast, αeff, of a sunspot is the irradiance deficit as seen at the surface of the sun; not from the earth. It is given by • DEF/(2 * PSI) • The bolometric contrast, when integrated over the solar sky of a sunspot, gives its luminosity deficit.

23. PSPT & SFO Deficits, μhems • DEF[PSPT(red)] = A + B * DEF[SFO(red)] + C * DEF[SFO(blue)] • A = 23 ± 28 μhem • B = 0.791 ± 0.168 • C = 0.214 ± 0.112 • R2 = 0.99 • N = 53

31. Annual Means

32. Student Involvement • Students carry out research with the help of faculty and staff. • Students are often co-authors of refereed papers. • The most recent example is Mike Wesolowski (Wesolowski et al. Solar Phys. 2008) who is in the Ph. D. program at Waterloo University.

33. Known or Potential Users • C. Fröhlich (VIRGO) • S. Dewitte (DIARAD) • J. Morrill (NRL) • J. Pap and H. Jones • T. Woods & SORCE team • J. Fontenla (LASP, Boulder) • G. DeToma (LASP) • G. Thiullier (PICARD) • R. Willson (ACRIMSAT)

34. Acknowledgements • The observations and analyses have been carried out by staff and many CSUN students, both undergraduate and graduate. • Work has been partially supported by grants over the years from both NASA and NSF.