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Aims. The main aim of the present analysis is to decipher (i) the small-scalebright features in solar images of the quiet Sun and active regions obtainedwith the Atacama Large Millimeter/submillimeter Array (ALMA) and (ii) the ALMAcorrespondence of various known chromospheric structures visible in the H-alphaimages of the Sun. Methods. Small-scale ALMA bright features in the quiet Sunregion were analyzed using single-dish ALMA observations (1.21 mm, 248 GHz) andin an active region using interferometric ALMA measurements (3 mm, 100 GHz).With the single-dish observations, a full-disk solar image is produced, whileinterferometric measurements enable the high-resolution reconstruction of partof the solar disk, including the active region. The selected quiet Sun andactive regions are compared with the H-alpha (core and wing sum), EUV, and softX-ray images and with the magnetograms. Results. In the quiet Sun region,enhanced emission seen in the ALMA is almost always associated with a strongline-of-sight (LOS) magnetic field. Four coronal bright points were identified,while other small-scale ALMA bright features are most likely associated withmagnetic network elements and plages. In the active region, in 14 small-scaleALMA bright features randomly selected and compared with other images, we foundfive good candidates for coronal bright points, two for plages, and five forfibrils. Two unclear cases remain: a fibril or a jet, and a coronal brightpoint or a plage. A comparison of the H-alpha core image and the 3 mm ALMAimage of the analyzed active region showed that the sunspot appears dark inboth images (with a local ALMA radiation enhancement in sunspot umbra), thefour plage areas are bright in both images and dark small H-alpha filaments areclearly recognized as dark structures of the same shape also in ALMA.

ALMA small-scale features in the quiet Sun and active regions