Determination of the Structure of the Coronal Magnetic Field Using Microwave Polarization Measurements

An analysis of the oscillatory motions and wave processes in active regions requires knowledge of the structure of the magnetic fields in the chromosphere and corona. We study the magnetic field structure of active regions at coronal heights, as they are determined by means of multiwave observations of polarized radio emission of active regions in the microwave range. Two methods, a stereoscopic method and the analysis of the radio spectrum are used. The method of stereoscopy rotation allows estimating the height of radio sources in a stable active region relative to the photosphere, based on its apparent motion in the image plane recorded over several days of observation. At various times one-dimensional scans at multiple frequencies spanning the 5.98 – 15.95 GHz frequency range from the RATAN-600 instrument are used. The gyroresonance emission mechanism, which is sensitive to the coronal magnetic field strength, is applied to convert the radio source estimated heights at various frequencies, h ( f ) , to information as regards magnetic field vs. height, B ( h ) . Diagrams of longitude – height of some polarized radio sources revealed multiple reversals, suggestive of a spiral magnetic structure. In all cases, the magnetic field strength maintains high values (800 – 1000 G) at the highest altitudes analysed, which reflects a relatively weak divergence in the field of magnetic flux tubes (in the height range 8 – 14 Mm) responsible for the main part of the radio emission of active regions.