Vladimir I. Garaimov

Detection of a cyclotron line in the radio spectrum of a solar active region and its interpretation

Observations of the active region AR 7962 obtained at 2–32 cm on the RATAN-600 radio telescope on May 10–12, 1996, are presented. The high-resolution measurements detected a narrow feature near 8.5 cm against the background of the smooth spectrum of the local source associated with sunspots. This narrow-band emission is identified with a bright, pointlike, high-frequency source at 1.7 cm recorded on maps made using the Nobeyama radio telescope. The characteristics of the observed line (lifetime 3 days, brightness temperature of the order of several million Kelvin, relative width of about 10%) suggest that it can be explained as thermal cyclotron radiation at the third harmonic of the electron gyrofrequency from a compact source containing a dense, hot plasma; the corresponding higher frequency emission could be due to thermal Bremsstrahlung. Analysis of the RATAN-600 and Nobeyama data can be used to probe the magnetic field, kinetic temperature, and electron density in the radiation source in the corona.

Ratan-600 observations of unusual inversion of polarization

Abstract We have made multiwavelength radio intensity and circular polarization observations of sunspot associated bipolar sources using RATAN-600 in the wave band 1.00 to 30 cm. We have found unusual inversion of the circular polarization of the microwave emission in both components of its bipolar structure at 14.5 cm. We explain the observed polarization by linear coupling, using a magnetic field parallel to the solar meridian, i.e. perpendicular to the plane connecting the spots of the group. This field may be a general magnetic field of the Sun, or some large-scale structure in the upper corona.