Improved reconstruction of total solar irradiance using broad- band facular contrast measurements from the Solar Bolometric Imager (SBI)

1
Improved reconstruction of total solar irradiance
using broad- band facular contrast measurements
from the Solar Bolometric Imager (SBI)

• The SBI images the solar photosphere with non-
  selective spectral response over the range 0.2
  2.6 micron i.e. 94 of the total solar irradiance
  (TSI).
• The first broad-band measurements of facular
  contrast were obtained during the first SBI
  flight on Sept 1 2003 ( Foukal et al., Ap.J.
  Letts, 611,57,2004).
• SBI is scheduled for re-flight from Antarctica in
  late 2006.

2
SBI facular contrast (left panel) used to
reconstruct TSI with no free parameters (right
panel) for the first time (Foukal et
al.,Ap.J.,submitted,Dec 2005). Note agreement in
TSI variation amplitude between reconstruction
and VIRGO radiometry, to better than /-10 rms.
This agreement indicates little contribution to
TSI variation from Teff variations outside spots
and faculae (e.g. magnetic stirring). It also
supports the thermal impedance model of TSI
variation over other mechanisms such as magnetic
storage or downdrafts.