First high-resolution look at the quiet Sun with ALMA at 3 mm

TL;DR

This paper presents high-resolution ALMA 3 mm observations of the quiet Sun, revealing detailed chromospheric structures, including the first detection of spicular features rising above the limb, demonstrating ALMA's potential for solar studies.

Contribution

First high-resolution ALMA 3 mm observations of the quiet Sun, including the detection of spicules and detailed chromospheric network analysis.

Findings

Chromospheric network is brighter than intranetwork by ~305 K.

Detected spicular structures up to 15" with brightness temperature ~1800 K.

ALMA images resemble 1600 Å images but with larger size.

Abstract

We present an overview of high resolution quiet Sun observations, from disk center to the limb, obtained with the Atacama Large mm and sub-mm Array (ALMA) at 3 mm. Seven quiet Sun regions were observed with resolution of up to 2.5" by 4.5". We produced both average and snapshot images by self-calibrating the ALMA visibilities and combining the interferometric images with full disk solar images. The images show well the chromospheric network, which, based on the unique segregation method we used, is brighter than the average over the fields of view of the observed regions by $\sim 305$ K while the intranetwork is less bright by $\sim 280$ K, with a slight decrease of the network/intranetwork contrast toward the limb. At 3 mm the network is very similar to the 1600 \AA\ images, with somewhat larger size. We detected for the first time spicular structures, rising up to 15" above the limb with a width down to the image resolution and brightness temperature of $\sim$ 1800 K above the local background. No trace of spicules, either in emission or absorption, was found on the disk. Our results highlight ALMA's potential for the study of the quiet chromosphere.