On the saturation of acoustic mode frequencies at high solar activity

Acoustic mode frequencies obtained by applying spherical harmonic decomposition to HMI, MDI and GONG observations were analysed throughout the solar cycle. Evidence of a deviation from a linear relation with solar radio flux was found indicating a saturation effect at high solar activity. The Gomper...

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Bibliographic Details
Published inarXiv.org
Main Author Rabello Soares, M Cristina
Format Paper Journal Article
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 06.04.2019
Subjects
Frequency shift
Physics - Solar and Stellar Astrophysics
Saturation
Solar activity
Solar cycle
Spherical harmonics
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Summary:Acoustic mode frequencies obtained by applying spherical harmonic decomposition to HMI, MDI and GONG observations were analysed throughout the solar cycle. Evidence of a deviation from a linear relation with solar radio flux was found indicating a saturation effect at high solar activity. The Gompertz model, which is one of the most frequently used sigmoid functions to fit growth data, is used. It is shown that its fitting to MDI and GONG data are statistically significant and a median saturation of four-hundred sfu is estimated. This saturation level is 50% larger than any obtained in the last century, hence the small effect observed in the minimum-to-maximum frequency shift. However, as shown here, it should not be disregarded.
ISSN:2331-8422
DOI:10.48550/arxiv.1904.03452