Info: Zenodo’s user support line is staffed on regular business days between Dec 23 and Jan 5. Response times may be slightly longer than normal.

Published February 26, 2021 | Version v1
Poster Open

The subterahertz solar cycle: Polar and equatorial radii derived from SST and ALMA

  • 1. Universidade Presbiteriana Mackenzie

Description

At subterahertz frequencies – i.e., millimeter and submillimeter wavelengths – there is a gap of measurements of the solar radius as well as other parameters of the solar atmosphere. As the observational wavelength changes, the radius varies because the altitude of the dominant electromagnetic radiation is produced at different heights in the solar atmosphere. Moreover, radius variations throughout long time series are indicative of changes in the solar atmosphere that may be related to the solar cycle. Therefore, the solar radius is an important parameter for the calibration of solar atmospheric models enabling a better understanding of the atmospheric structure. In this work we use data from the So- lar Submillimeter-wave Telescope (SST) and from the Atacama Large Millimeter/submillimeter Array (ALMA), at the frequencies of 100, 212, 230, and 405 GHz, to measure the equatorial and polar radii of the Sun. The radii measured with extensive data from the SST agree with the radius-vs-frequency trend present in the literature. The radii derived from ALMA maps at 230 GHz also agree with the radius-vs-frequency trend, whereas the 100-GHz radii are slightly above the values reported by other authors. In addition, we analyze the equatorial and polar radius behavior over the years, by determining the correlation coefficient between solar activity and subterahertz radii time series at 212 and 405 GHz (SST). The variation of the SST-derived radii over 13 years are correlated to the solar activity when considering equatorial regions of the solar atmosphere, and anticorrelated when considering polar regions. The ALMA derived radii time series for 100 and 230 GHz show very similar behaviors with those of SST.

Files

Cool_Stars_20.5_poster2.pdf

Files (1.5 MB)

Name Size Download all
md5:ff78afd7104d7b1801e903653fd1eec2
626.4 kB Preview Download
md5:4f4f9a8d1f0f86e47e8bcf67c44140c1
860.8 kB Preview Download