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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20101216T000000
DTEND;TZID=Atlantic/Canary:20101216T010000
UID:iactalks-232
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/232
CREATED:2010-12-16T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:(1) The effect of magnetic fields on solar abundance determinations
  (2) The solar photosphere in 3D. This time from observations
DESCRIPTION:(1) The effect of magnetic fields on solar abundance determinat
 ions (2) The solar photosphere in 3D. This time from observations\nDr. Dam
 ian Fabbian, Dr. Héctor Socas-Navarro\n\n(1) In a recently published diff
 erential analysis (see  Fabbian et al) we have derived abundance correctio
 ns for iron lines, using synthetic spectra from solar magneto-convection s
 imulations that were performed via running the Copenhagen stagger-code on 
 massively-parallel clusters. The series of 3D snapshots used for the spect
 ral synthesis covers 2.5 solar hours in the statistically stationary regim
 e of the convection.  Crucially, we show that the effect of magnetic field
 s on solar abundance determinations cannot be neglected. This is equally v
 alid for all three different Fe abundance indicators which we have studied
 , though the sign of the abundance correction changes depending on the int
 erplay of the magnetic-sensitivity of the spectral line under consideratio
 n and of temperature structure variations.   Interestingly, for two of the
  abundance indicators (respectively, at 608.27nm and 624.07 nm) that were 
 used in  Asplund et al's  analysis and that we also included in our invest
 igation, the presence of a magnetic field has a predominantly indirect (i.
 e., due to temperature changes between MHD and HD models) effect, leading 
 to positive abundance corrections (since the final equivalent width of tho
 se Fe I lines is found to decrease with increasing magnetic flux). The dir
 ect magnetic effect due to Zeeman broadening dominates instead for the 156
 4.85 nm absorption line, causing for it increasingly negative abundance co
 rrections when making the initially implanted magnetic flux larger.    (2)
  A new three-dimensional model of the solar photosphere is presented in th
 is paper and made publicly available to the community. This model has the 
 peculiarity that it has been obtained by inverting spectro-polarimetric ob
 servations, rather than from numerical radiation hydrodynamical simulation
 s. The data used here are from the spectro-polarimeter on-board the Hinode
  satellite, which routinely delivers Stokes I, Q, U and V profiles in the 
 6302 Å spectral region with excellent quality, stability and spatial
  resolution (approximately 0.3''). With such spatial resolution, the major
  granular components are well resolved, which implies that the derived mod
 el needs no micro- or macro-turbulence to properly fit the widths of the o
 bserved spectral lines. Not only this model fits the observed data used fo
 r its construction, but it can also fit previous solar atlas observations 
 satisfactorily.
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