Millimeter Observations at ALMA and in the Microwave Range with RATAN-600. Comparison for Active Regions on the Sun

Abstract

The distributions of temperature and density in the sunspot atmosphere are crucial for an understanding of the process of energy transfer from the photosphere upward to the corona in strong magnetic fields. The joint analysis of millimeter observations at ALMA (Atacama Large Millimeter/Submillimeter Array) and observations performed in the microwave range (centimeter wavelengths) with the RATAN-600 radio telescope of the Russian Academy of Sciences provides new data on the temperature distribution and physical processes at different altitudes above a spot. The NOAA 12470 active region was observed and mapped at 1.3 and 3 mm (ALMA) and 2–10 cm (RATAN-600) in December 2015. These observations are analyzed, and the results are compared to models of sunspot atmospheres. The fundamental problems arising in the study of atmospheres of active regions in the millimeter and centimeter ranges are determined, and the importance of the 3–18 mm range in the physics of the generation and transfer of energy for corona heating is demonstrated.