@InProceedings{SelhorstCostSilv:2006:StMaFi,
               author = "Selhorst, Caius Lucius and Costa, Joaquim Eduardo Rezende and 
                         Silva, Adriana V{\'a}lio Roque",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {CRAAM/ Mackenzie}",
                title = "Study of magnetic fields in solar active regions from radio 
                         observations",
            booktitle = "Anais...",
                 year = "2006",
         organization = "Reuni{\~a}o Anual da Sociedade Astron{\^o}mica Brasileira, 32.",
             abstract = "In this work we present the results of our 3-D atmospheric model 
                         over solar active regions. Active regions are sites of increased 
                         magnetic fields in the solar atmosphere. Our model considers the 
                         temperature and densities (electrons and ions) distributions with 
                         height, as well the local magnetic 3-D structure. To obtain the 
                         positions and intensities of magnetic field lines in the solar 
                         atmosphere, we made force-free extrapolations of the magnetic 
                         field from the intensities measured in the MDI (SOHO) 
                         magnetograms, which present the mean photospheric magnetic field 
                         intensity with a resolution of about 2 arcsec. This procedure 
                         resulted in three data cubes with magnetic field intensities, one 
                         for each vector component. Magnetic loops are simulated by filling 
                         the region around each magnetic field line with densities and 
                         temperature values distinct from those of the quiet solar 
                         atmosphere. Thus, the atmospheric region is formed by the presence 
                         of flux tubes. For each column of the cube representing the 
                         atmosphere, the equations of radiative transport were solved 
                         considering bremsstrahlung and gyro-resonance emission at 17 GHz. 
                         This procedure yields 2-D matrices of brightness temperature, that 
                         were compared with the observational results at 17 GHz taken by 
                         the Nobeyama Radioheliograph (NoRH). The results showed that in 
                         faint non-polarized active regions (TB=5´104K), the gyro-resonance 
                         emission is negligible compared to the bremsstrahlung 
                         contribution, that is independent of magnetic field intensities. 
                         On the other hand, for a polarized active region with brightness 
                         temperature TB=4´105K, the gyro-resonance became very important 
                         for the total 17 GHz emission. Nevertheless, our model showed that 
                         the gyro-resonance emission calculated from the magnetic field 
                         extrapolation obtained from the MDI magnetograms is totally 
                         absorbed by solar atmosphere. To overcome this problem we solved 
                         the transfer equations with magnetic field concentrations similar 
                         to other results present in the literature. Here, we set the fine 
                         structures of flux tubes with magnetic field intensities about 
                         twice the values showed in the magnetograms.",
  conference-location = "Atibaia, SP",
      conference-year = "30 jul - 03 ago",
                label = "self-archiving-INPE-MCTIC-GOV-BR",
             language = "pt",
         organisation = "Sociedade Astron{\^o}mica Brasileira",
           targetfile = "selhorst_study.pdf",
        urlaccessdate = "06 maio 2024"
}