LESIA - Observatoire de Paris

Inversion of spectropolarimetric data for vector magnetic field maps, taking into account unresolved magnetic structures

jeudi 21 janvier 2016, par Véronique Bommier (LESIA)

Mercredi 10 février 2016 à 11h00 , Lieu : Salle de réunion du bâtiment 14

This method has been developed at LESIA and is based on the UNNOFIT inversion code (Landolfi, Landi Degl’Innocenti, Arena, 1984, Sol. Phys., 93, 269). This code applies the Levenberg-Marquardt algorithm to make coincide the observed Stokes profiles with the theoretical ones stemmed from the Unno-Rachkovsky integration of the transfer equation through a Milne-Eddington atmosphere model. The work developed at LESIA has consisted in taking into account unresolved magnetic structures, by introducing an additional parameter to determine, a lower than unity magnetic filling factor. We will show that, in sunspot center, the results coincide with those obtained without this feature, because in sunspot umbra the magnetic filling factor is unity. But the farther from the sunspot center, the more different is the retrieved field inclination, and other observation results confirm the UNNOFIT ones. HMI onboard SDO records spectropolarimetric data of the full disk every 12 mn, and the data are available for downloading. It is then possible to select an active region of interest, and to prepare UNNOFIT field vectors of it. Examples of such work done on request by some LESIA solar team members, will be cited. This seminar is devoted to advertise about this possibility available at LESIA. The online HMI/SDO field vectors are obtained without assuming any magnetic filling factor. The farther from the sunspot center, the more different they are from the UNNOFIT results.


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