The Atacama Large Millimeter-submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12 m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that utilizes the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions we derive quiet-Sun values at disk center of 7300 K at λ = 3 mm and 5900 K at λ = 1.3 mm. These values have statistical uncertainties of order 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of order 25 ′′ , the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range. Active regions and plage are amongst the hotter features while a large sunspot umbra shows up as a depression and filament channels are relatively cool. Prominences above the solar limb are a common feature of the single-dish images.

The goal of this paper is to investigate Reynolds stresses and to check if it is plausible that they are responsible for angular momentum transfer toward the solar equator. We also analysed meridional velocity, rotation velocity residuals and correlation between the velocities. We used sunspot groups position measurements from GPR (Greenwich Photographic Result) and SOON/USAF/NOAA (Solar Observing Optical Network/United States Air Force/National Oceanic and Atmospheric Administration) databases covering the period from 1878 until 2011. In order to calculate velocities we used daily motion of sunspot groups. The sample was also limited to ±58 • in Central Meridian Distance (CMD) in order to avoid solar limb effects. We mainly investigated velocity patterns depending on solar cycle phase and latitude. We found that meridional motion of sunspot groups is toward the centre of activity from all available latitudes and in all phases of the solar cycle. The range of meridional velocities is ±10 m s −1 . Horizontal Reynolds stress is negative at all available latitudes and indicates that there is a minimum value (q ≈ -3000 m 2 s −2 ) located at b ≈ ±30 • . In our convention this means that angular momentum is transported toward the solar equator in agreement with the observed rotational profile of the Sun.

Observations of the Sun at millimeter and submillimeter wavelengths offer a unique probe into the structure, dynamics, and heating of the chromosphere; the structure of sunspots; the formation and eruption of prominences and filaments; and energetic phenomena such as jets and flares. High-resolution observations of the Sun at millimeter and submillimeter wavelengths are challenging due to the intense, extended, lowcontrast, and dynamic nature of emission from the quiet Sun, and the extremely intense and variable nature of emissions associated with energetic phenomena. The Atacama Large Millimeter/submillimeter Array (ALMA) was designed with solar observations in mind. The requirements for solar observations are significantly different from observations of sidereal sources and special measures are necessary to successfully carry out this type of observations. We describe the commissioning efforts that enable the use of two frequency bands, the 3 mm band (Band 3) and the 1.25 mm band (Band 6), for continuum interferometric-imaging observations of the Sun with ALMA. Examples of high-resolution synthesized images obtained using the newly commissioned modes during the solar commissioning campaign held in December 2015 are presented. Although only 30 of the eventual 66 ALMA antennas were used for the campaign, the solar images synthesized from the ALMA commissioning data reveal new features of the solar atmosphere that demonstrate the potential power of ALMA solar observations. The ongoing expansion of ALMA and solar-commissioning efforts will continue to enable new and unique solar observing capabilities.

Context. Coronal bright points (CBP) are ubiquitous small brightenings in the solar corona associated with small magnetic bipoles. Aims. We derive the solar differential rotation profile by tracing the motions of CBPs detected by the Atmospheric Imaging Assembly (AIA) instrument aboard the Solar Dynamics Observatory (SDO). We also investigate problems related to the detection of CBPs resulting from instrument and detection algorithm limitations. Methods. To determine the positions and identification of CBPs we used a segmentation algorithm. A linear fit of their central meridian distance and latitude vs time was used to derive velocities. Results. We obtained 906 velocity measurements in a time interval of only 2 days. The differential rotation profile can be expressed as ω rot = (14.• 47 ± 0.• 10 + (0.• 6 ± 1.• 0) sin 2 (b) + (−4.• 7 ± 1.• 7) sin 4 (b)) d −1 . Our result is in agreement with other work and it comes with reasonable errors in spite of the very short time interval used. This was made possible by the higher sensitivity and resolution of the AIA instrument compared to similar equipment as well as high cadence. The segmentation algorithm also played a crucial role by detecting so many CBPs, which reduced the errors to a reasonable level. Conclusions. Data and methods presented in this paper show a great potential for obtaining very accurate velocity profiles, both for rotation and meridional motion and, consequently, Reynolds stresses. The amount of CBP data that could be obtained from this instrument should also provide a great opportunity to study changes of velocity patterns with a temporal resolution of only a few months. Other possibilities are studies of evolution of CBPs and proper motions of magnetic elements on the Sun.

Context. Various solar features can be seen in emission or absorption on maps of the Sun in the millimeter and submillimeter wavelength range. The recently installed Atacama Large Millimeter/submillimeter Array (ALMA) is capable of observing the Sun in that wavelength range with an unprecedented spatial, temporal and spectral resolution. To interpret solar observations with ALMA the first important step is to compare solar ALMA maps with simultaneous images of the Sun recorded in other spectral ranges. Aims. The first aim of the present work is to identify different structures in the solar atmosphere seen in the optical, infrared and EUV parts of the spectrum (quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points) in a full disc solar ALMA image. The second aim is to measure the intensities (brightness temperatures) of those structures and to compare them with the corresponding quiet Sun level. Methods. A full disc solar image at 1.21 mm obtained on December 18, 2015 during a CSV-EOC campaign with ALMA is calibrated and compared with full disc solar images from the same day in Hα line, in He I 1083 nm line core, and with various SDO images (AIA at 170 nm, 30.4 nm, 21.1 nm, 19.3 nm, and 17.1 nm and HMI magnetogram). The brightness temperatures of various structures are determined by averaging over corresponding regions of interest in the calibrated ALMA image. Results. Positions of the quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points are identified in the ALMA image. At the wavelength of 1.21 mm active regions appear as bright areas (but sunspots are dark), while prominences on the disc and coronal holes are not discernible from the quiet Sun background, although having slightly less intensity than surrounding quiet Sun regions. Magnetic inversion lines appear as large, elongated dark structures and coronal bright points correspond to ALMA bright points. Conclusions. These observational results are in general agreement with sparse earlier measurements at similar wavelengths. The identification of coronal bright points represents the most important new result. By comparing ALMA and other maps, it was found that the ALMA image was oriented properly and that the procedure of overlaying the ALMA image with other images is accurate at the 5 arc sec level. The potential of ALMA for physics of the solar chromosphere is emphasized.