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

Autor(es)

Menezes, Fabian ^[1] ; Selhorst, Caius L. ^[2] ; Gimenez de Castro, Carlos Guillermo ^{[3, 1]} ; Valio, Adriana ^[1]

Afiliação do(s) autor(es)

^[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

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 910, n. 1 MAR 2021.
• Citações Web of Science: 1

Resumo

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)

• Processo FAPESP: 13/24155-3 - Diagnóstico de explosões solares em inédito intervalo espectral, de micro-ondas até frequências THz: desafios para interpretação (FLAT)
• Beneficiário: Carlos Guillermo Giménez de Castro
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 19/03301-8 - Observação e modelagem de regiões ativas solares e estelares em ondas rádio mm/sub-mm
• Beneficiário: Caius Lucius Selhorst
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 13/10559-5 - Investigação de fenômenos de altas energias e plasmas astrofísicos: teoria, simulações numéricas, observações e desenvolvimento de instrumentação para o Cherenkov Telescope Array (CTA)
• Beneficiário: Elisabete Maria de Gouveia Dal Pino
• Modalidade de apoio: Auxílio à Pesquisa - Temático