Application of Recovering Procedures to RT-32 Radio Maps of the Sun

Abstract

The generalized maximum entropy method (GMEM) is proven to recover both positive and negative local microwave sources on the 2.7 cm maps of the Sun taken with the radiotelescope RT-32 of the Ventspils International Radio Astronomy Center (VIRAC). The maps of the Sun need to be recovered due to high intensity of the side lobes of the RT-32 diagram pattern − up to 30% at 2.7 cm. The presence of negative local sources associated with Hα filaments is inferred from the 2.7 cm maps of the Sun (RT-32) compared with the 1.76 cm maps of the Sun (Nobeyama Radio Heliograph).

Prospects of Solar Microwave Observations at the Ventspils Radio-Astronomy Center

“…• organization and support of a "raw" and processed data multilevel archive available to any investigator. The solar observations group of the VIRAC is developing some numerical techniques (CLEAN and MEM) to eliminate the telescope's aberrations [2] as well as to simulate the generation and propagation of microwaves in the solar atmosphere [3].…”

Low Brightness Temperature in Microwaves at Periphery of Some Solar Active Regions

“…An attempt to restore the low-contrast microwave structures on the maps of the Sun, which were scanned with the Ventspils International Radio-Astronomy Center RT-32 radio telescope, was undertaken in [1]. In 2012, a new multichannel spectral polarimeter was installed on the 32-meter antenna [2], and a number of observations were performed in 2013-2014.…”

“…It should be noted that the positioning of the RT-32 diagram pattern was revised ( Fig. 1a) since the results of [1]. The RT-32 with the solar spectral polarimeter makes available 16 maps in each Stokes I and V per session of scanning [13].…”