scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
A cross-comparison of magnetograms in spectral lines NiI 676.77 nm, FeI 63.025 nm,
FeI 617.33 nm, and calibration issue of solar magnetic field measurements on space
missions SOHO, HINODE and SDO
Demidov Mikhail
Institute of Solar-Terrestrial Physics
Reliable information about distribution of magnetic fields across the whole solar surface is
necessary for many scientific tasks. The existence of severe difficulties in this problem is
proved, for an example, by several recalibrations of the widely used SOHO/MDI data sets.
The main aim of this study is a cross-comparison of magnetic field observations made in
different spectral lines used on space missions SOHO and Hinode, which measurements are
available for several years already, and SDO, which data are expected in a nearest future.
These lines are: Ni I 676.77 nm (SOHO/MDI), FeI 630.15 nm and FeI 63.025 nm
(Hinode/SP), FeI 617.33 nm (SDO/HMI).
To do that, the full-disk high-precision Stokes-meter measurements on the STOP telescope at
Sayan observatory are used basically, as well as some data from SOHO and Hinode. Besides,
observations in other spectral lines having a great diagnostics impact, such as FeI 525.02 nm,
FeI 523. 29 nm and FeI 532.4 2 nm are analyzed. The difference between simultaneous or
quasi-simultaneous observations in different spectral lines on the STOP do not exceeds factor
by 2-3 depending on combination of spectral lines and position on solar disk. This is
significantly less then in some other studies devoted to cross-comparison of different data
sets. Importance and consequences of the obtained results are discussed.