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Solar Radius at Sub-Terahertz Frequencies

Published online by Cambridge University Press:  12 September 2017

Fabian Menezes  and
Adriana Valio
Fabian Menezes
Affiliation:
Center for Radio Astronomy and Astrophysics (CRAAM)Mackenzie Presbyterian University, São Paulo, Brazil email: fabianme17@gmail.com, avalio@craam.mackenzie.br
Adriana Valio
Affiliation:
Center for Radio Astronomy and Astrophysics (CRAAM)Mackenzie Presbyterian University, São Paulo, Brazil email: fabianme17@gmail.com, avalio@craam.mackenzie.br
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Abstract

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The visible surface of the Sun, or photosphere, is defined as the solar radius in the optical spectrum range located at 696,000 km (Cox et al. (Ed. 2015)). However, as the altitude increases, the dominant electromagnetic radiation is emitted at other frequencies. Our aim is to measure the solar radius at frequencies of 212 GHz and 405 GHz through out a solar cycle and, therefore, the altitude where these emissions are generated and that variation along the years. Also we tried to verify the the radius dependence on the solar activity cycle, which can be a good indicator of the changes that occur in the atmosphere structure. For this, we used data obtained by the Submillimetric Solar Telescope (SST) created from daily scans made by SST from 1990 to 2015. From these scans a 2D map of the solar disk was constructed. The solar radius is then determined by adjusting a circumference to the points where the brightness is half of the quiet Sun level, which is set as the most common temperature value in the solar map, i.e., the mode of the temperature distribution. Thus, we determined the solar radius at 212 and 405 GHz and the altitude of the emissions respectively. For 212 GHz, we obtained a radius of 976.5”±8” (707±4 Mm), whereas for 405 GHz, we obtained 975.0”±8” (707±5 Mm). optical spectrum range

Keywords

Sun: activitySun: chromosphereSun: fundamental parametersSun: radio radiation
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S328: Living Around Active Stars , October 2016 , pp. 113 - 116
Copyright
Copyright © International Astronomical Union 2017 

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