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Auteurs principaux:	Reda, Raffaele, Penza, Valentina
Format:	Preprint
Publié:	2024
Sujets:	Solar and Stellar Astrophysics
Accès en ligne:	https://arxiv.org/abs/2405.17078
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author	Reda, Raffaele Penza, Valentina
author_facet	Reda, Raffaele Penza, Valentina
contents	The solar activity, which is driven by a variable magnetic field, exhibits changes along several time scales, the 11-year being the most known. In addition to the SunSpot Number, the Ca II K index and the Mg II index are indices widely employed among those proposed to quantify the solar activity, also because of their ability to trace the solar UV emission. In this work, we compare the Ca II K 0.1nm emission index to the Mg II index over the time interval 1978-2017, which covers almost four solar cycles. We show that they are strongly correlated across each solar cycle (r$\geq$0.94), providing the corresponding linear regression fit parameters. The Hilbert-Huang Transform is then used to decompose such indices into their intrinsic mode of oscillation. By studying how their components are correlated over the different time scales, it is found that the maximum correlation is observed at the 11-year scale, while the correlation is less strong going to smaller time scales.
format	Preprint
id	arxiv_https___arxiv_org_abs_2405_17078
institution	arXiv
publishDate	2024
record_format	arxiv
spellingShingle	The Ca II K index-Mg II index relation: A Hilbert-Huang Transform approach Reda, Raffaele Penza, Valentina Solar and Stellar Astrophysics The solar activity, which is driven by a variable magnetic field, exhibits changes along several time scales, the 11-year being the most known. In addition to the SunSpot Number, the Ca II K index and the Mg II index are indices widely employed among those proposed to quantify the solar activity, also because of their ability to trace the solar UV emission. In this work, we compare the Ca II K 0.1nm emission index to the Mg II index over the time interval 1978-2017, which covers almost four solar cycles. We show that they are strongly correlated across each solar cycle (r$\geq$0.94), providing the corresponding linear regression fit parameters. The Hilbert-Huang Transform is then used to decompose such indices into their intrinsic mode of oscillation. By studying how their components are correlated over the different time scales, it is found that the maximum correlation is observed at the 11-year scale, while the correlation is less strong going to smaller time scales.
title	The Ca II K index-Mg II index relation: A Hilbert-Huang Transform approach
topic	Solar and Stellar Astrophysics
url	https://arxiv.org/abs/2405.17078

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