The three-dimensional structure of the corona above active region NOAA 9591 from microwave observations |
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| Authors: | N G Peterova B V Agalakov T P Borisevich A N Korzhavin B I Ryabov |
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| Institution: | (1) St. Petersburg Branch of the Special Astrophysical Observatory, St. Petersburg, Russia;(2) Institute of Solar-Terrestrial Physics, Irkutsk, Russia;(3) Main Astronomical Observatory, Pulkovo, St. Petersburg, Russia;(4) Astronomical Institute, University of Latvia, Riga, Latvia |
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| Abstract: | We study the active region NOAA 9591 using observations at 1.92–10.17 cm obtained on two large Russian radio instruments: the RATAN-600 radio telescope and the Siberian Solar Radio Telescope. The active region was associated with an isolated spot at the photospheric level, whose magnetic field had a well-defined Delta configuration. The radio observations show that the structure of the coronal source located above the spot cannot be described in a simple (unipolar) cyclotron model. A comparison with X-ray observations indicates that the three-dimensional structure of the corona above the spot can be represented as a strongly elongated loop whose apex resembles a cusp brightening (a qualitative model for the structure is presented). Unexpectedly, radiation with a high degree of polarization (～25%) was detected far (～100 000 km) from the photosphere. The need for a quantitative model for coronal sources above the strong Delta-configuration magnetic fields, which are known to play an important role in active solar processes (flares, phenomena such as coronal-mass ejections) is outlined. Thanks to its simple morphology, which enabled the identification of a pure Delta configuration, the active region NOAA 9591 provides high-quality observational material for the creation of such a model. |
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