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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

The Subterahertz Solar Cycle: Polar and Equatorial Radii Derived from SST and ALMA

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Author(s):
Menezes, Fabian [1] ; Selhorst, Caius L. [2] ; Gimenez de Castro, Carlos Guillermo [3, 1] ; Valio, Adriana [1]
Total Authors: 4
Affiliation:
[1] Univ Presbiteriana Mackenzie, Ctr Radio Astron & Astrofis Mackenzie CRAAM, Sao Paulo - Brazil
[2] Univ Cidade Sao Paulo, Univ Cruzeiro Sul, Nucleo Astrofis, Sao Paulo, SP - Brazil
[3] UBA, CONICET, Inst Astron & Fis Espacio, Buenos Aires, DF - Argentina
Total Affiliations: 3
Document type: Journal article
Source: ASTROPHYSICAL JOURNAL; v. 910, n. 1 MAR 2021.
Web of Science Citations: 1
Abstract

At subterahertz frequencies-i.e., millimeter and submillimeter wavelengths-there is a gap in 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 Solar Submillimeter-wave Telescope (SST) and the Atacama Large Millimeter/submillimeter Array (ALMA) at 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-versus-frequency trend present in the literature. The radii derived from ALMA maps at 230 GHz also agree with the radius-versus-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 radius time series at 212 and 405 GHz (SST). The variations of the SST-derived radii over 13 yr are correlated to the solar activity when considering equatorial regions of the solar atmosphere and anticorrelated when considering polar regions. The ALMA-derived radius time series for 100 and 230 GHz show very similar behaviors with those of SST. (AU)

FAPESP's process: 19/03301-8 - Observation and models of solar and stellar active regions at radio wavelengths (mm/sub-mm)
Grantee:Caius Lucius Selhorst
Support type: Regular Research Grants
FAPESP's process: 13/24155-3 - Solar flare diagnostic in an unprecedented frequency range from microwaves to THz frequencies: challenges for interpretation (flat)
Grantee:Carlos Guillermo Giménez de Castro
Support type: Research Projects - Thematic Grants
FAPESP's process: 13/10559-5 - Investigation of high energy and plasma astrophysics phenomena: theory, numerical simulations, observations, and instrument development for the Cherenkov Telescope Array (CTA)
Grantee:Elisabete Maria de Gouveia Dal Pino
Support type: Research Projects - Thematic Grants