engleski

A COMPARISON OF SOLAR ALMA OBSERVATIONS AND MODEL BASED PREDICTIONS OF THE BRIGHTNESS TEMPERATURE

The new fa ility Ata ama Large Millimeter/submillimeter Array (ALMA) is apable of observing the Sun in the wavelength range from 0.3 mm to 10 mm with an unpre edented spatial, temporal and spe tral resolution. The rst aim of the present work is to identify dierent stru tures in the solar atmosphere (quiet Sun, a tive regions, laments on the dis , and oronal holes) in a full dis solar ALMA image at 1.21 mm obtained on De ember 18, 2015 during a CSV-EOC ampaign. It is ompared with full dis solar images from the same day in the H line (Cerro Tololo Observatory, NISP), and at three EUV wavelengths (30.4 nm, 21.1 nm, 17.1 nm ; a omposite SDO image). Positions of the quiet Sun areas, a tive regions, laments on the dis , and oronal holes are identied in the ALMA image. To interpret solar observations with ALMA it is important to ompare the measured and al ulated intensities of various solar stru tures. So, the se ond aim of this work is to al ulate the intensity (brightness temperature) for those stru tures (quiet Sun, a tive regions, laments on the dis , and oronal holes) for a broad wavelength range (from 0.3 mm to 10 mm), losely related to that of the ALMA, and to ompare the results with available ALMA observations. Thermal bremsstrahlung is the dominant radiation me hanism for explanation of the observed phenomena. A pro edure for al ulating the brightness temperature for a given wavelength and model atmosphere, whi h integrates the radiative transfer equation for thermal bremsstrahlung, is used. At the wavelength of 1.21 mm a tive regions appear as bright areas, while laments on the dis and oronal holes are not dis ernible from the quiet Sun ba kground. The models generally agree with the observed results: A tive regions are bright primarily due to higher densities, laments an appear bright, dark or not at all and oronal holes annot be easily identied.

Sun: radio radiation - Sun: hromosphere - Sun: transition region - Sun: orona 1.

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