Study of magnetic fields in solar active regions from radio observations

Details Study of magnetic fields in solar active regions from radio observations Study of magnetic fields in solar active regions from radio observations

Publishing date

Aug 2006

URL

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...3e..24s&link_type=abstract

Journals

Solar Active Regions and 3D Magnetic Structure, 26th meeting of the IAU, Joint Discussion 3, 16-17 August, 2006, Prague, Czech R

Science

Other

Type

Scientific paper

Abstract

In this work we present the results of our 3D atmospheric model over solar active regions. Our model considers the temperature and density distributions with height, as well the local magnetic 3D structure. To obtain the positions and intensities of magnetic field lines in the solar atmosphere, we made force-free extrapolations of the magnetic field intensities measured in the MDI (SOHO) magnetograms. 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 2D 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 (T[B]=5 x 10^4K), 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 T[B]=4 x 10^5K, 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.

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