Recent results of multiwavelength observations with the radio telescope RATAN-600
Tatiana Kaltman, Special Astrophysical observatory
We present the latest results obtained from the analysis of the RATAN-600 (Radio Astronomical Telescope of the Russian Academy of Sciences) observations in a wide range of wavelengths (3-18 GHz, in Stokes parameters I and V). The technical characteristics of the instrument make it possible to study solar radio emission of a variety of objects of different physical nature: from the chromosphere to the lower corona, from low-contrast supergranulation network and coronal holes to powerful bursts; the entire magnetosphere of active regions including spot sources, peculiar sources, halo, floccules and coronal loops. RATAN observations are also capable of providing data on fast events such as CME and jets.
It is particularly important to carry out these studies, combining radio observations with data from optical, ultraviolet and X-ray instruments; extending magnetic field measurements with its modeling extrapolations into the corona, and taking into consideration various modeling methods to diagnose physical parameters of the emitting plasma. In this contribution we present recent examples of such studies. We used simulations and combined observations with RATAN-600 and ALMA to study solar atmosphere above sunspots. The simulations of spot radiation at short wavelengths allowed to reveal its lesser known properties such as the contribution of the 4-th harmonic of the gyro-radiation in extraordinary mode and the depression of the free-free radiation in ordinary mode.
We also present an example of a fast-changing event. Based on the data from RATAN-600, RHESSI, and SDO spacecrafts, the analysis of the fine temporal structure of radiation in the solar B-class microflare was carried out. The quasi-periodic pulsations of radio emission with periods of 1.4 and 0.7 c were found. The registered temporal behavior of the parameter V in the RATAN-600 data showed the presence of the misbalance of the left- and right-hand polarized signals. This misbalance was interpreted as some asymmetry of nonthermal electron jets propagating downwards along the opposite legs of a flare loop. The properties of radio emission modulated by the pulsations, the geometry of the flaring region and associated spectrum of X-ray radiation allowed to interpret this event as a manifestation of the fast magnetoacoustic sausage oscillations of flaring loops.
This work is supported by Grant 18-29-21016 and by Grant 18-02-00045 of the Russian Foundation for Basic Research.