First high-resolution look at the quiet Sun with ALMA

Alexander Nindos, University of Ioannina

We present an overview of two sets of high resolution quiet Sun observations obtained with the Atacama Large mm and sub-mm Array (ALMA). The first set consisted of observations of seven regions from disk center to the limb at 3 mm, while the second set consisted of observations of a region close to disk center obtained sequentially at 1 mm and 3 mm. We produced both average and snapshot images by self-calibrating the ALMA visibilities and combining the interferometric images with full disk solar images. The spatial resolution of the images was better than 2.5'' by 4.5'' while their cadence was 1-2 s. The images show well the chromospheric network with a slight decrease of network/intranetwork contrast toward the limb. We detected spicular structures, rising up to 15'' above the limb with a width down to the image resolution and brightness temperature of ~1800 K above the local background. No trace of spicules, either in emission or absorption, was found on the disk. Several transient features were detected during the observations. We also observed p-mode oscillations with a peak frequency of 3.6 mHz. Our results highlight ALMA’s potential for the study of the quiet chromosphere.