Solar Cycle Indices from the Photosphere to the Corona: Measurements and Underlying Physics

Ermolli, I.; Shibasaki, Κ.; Tlatov, A. G.; Driel‐Gesztelyi, L. van

doi:10.1007/978-1-4939-2584-1_4

Cited by 4 publications

(5 citation statements)

References 138 publications

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“…They are also indispensable to reconstructions of past irradiance variations (see, e.g., Solanki et al, 2013). There are various other chromospheric data (Ermolli et al, 2015) that can provide information on plage regions, such as the series of the 10.7 cm radio flux (available since 1947; Tapping and Morton, 2013), Lyman α emission (available since 1969; Woods et al, 2000), Mg II index (available since 1978;Heath and Schlesinger, 1986;Snow et al, 2014), He I (10830Å) equivalent width (since 1977); Ca II (8542Å) central depth (since 1978), Hα central depth (since 1984), CN (3883 Å) bandhead index (since 1979;Livingston et al, 2007), and Ca II K 0.5 or 1 Å disc-integrated emission index (since 1974; White et al, 1998). However, all these measurements cover significantly shorter periods of time and are disc-integrated quantities, carrying less information than the full-disc Ca II K observations.…”

mentioning

confidence: 99%

Full-disc Ca ii K observations—A window to past solar magnetism

Chatzistergos

Krivova

Ermolli

2022

Front. Astron. Space Sci.

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Full-disc observations of the Sun in the Ca ii K line provide one of the longest collections of solar data. First such observations were made in 1892 and since then various sites around the world have carried out regular observations, with Kodaikanal, Meudon, Mt Wilson, and Coimbra being some of the most prominent ones. By now, Ca ii K observations from over 40 different sites allow an almost complete daily coverage of the last century. Ca ii K images provide direct information on plage and network regions on the Sun and, through their connection to solar surface magnetic field, offer an excellent opportunity to study solar magnetism over more than a century. This makes them also extremely important, among others, for solar irradiance reconstructions and studies of the solar influence on Earth’s climate. However, these data also suffer from numerous issues, which for a long time have hampered their analysis. Without properly addressing these issues, Ca ii K data cannot be used to their full potential. Here, we first provide an overview of the currently known Ca ii K data archives and sources of the inhomogeneities in the data, before discussing existing processing techniques, followed by a recap of the main results derived with such data so far.

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confidence: 99%

Full-disc Ca ii K observations—A window to past solar magnetism

Chatzistergos

Krivova

Ermolli

2022

Front. Astron. Space Sci.

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“…In this regard, several methods were proposed to estimate the optimal embedding dimension m (see e.g. Fredkin & Rice 1995;Rhodes & Morari 1997). In particular, Sello (2001), using the false neighbor method (see for instance Kennel et al 1992;Abarbanel et al 1993), found that the minimum embedding dimension for the sunspot number is m = 5.…”

Section: Methodsmentioning

confidence: 99%

“…Several indices have been introduced in order to represent the many different observables modulated by the solar cycle (Hathaway 2010;Ermolli et al 2014).…”

Section: Data Setmentioning

confidence: 99%

Recurrence quantification analysis of two solar cycle indices

Stangalini¹,

Ermolli²,

Consolini³

et al. 2017

J. Space Weather Space Clim.

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Solar activity affects the whole heliosphere and near-Earth space environment. It has been reported in the literature that the mechanism responsible for the solar activity modulation behaves like a low-dimensional chaotic system. Studying these kind of physical systems and, in particular, their temporal evolution requires non-linear analysis methods. To this regard, in this work we apply the recurrence quantification analysis (RQA) to the study of two of the most commonly used solar cycle indicators; i.e. the series of the sunspot number (SSN), and the radio flux 10.7 cm, with the aim of identifying possible dynamical transitions in the system; a task which is particularly suited to the RQA. The outcome of this analysis reveals the presence of large fluctuations of two RQA measures: namely the determinism and the laminarity. In addition, large differences are also seen between the evolution of the RQA measures of the SSN and the radio flux. That suggests the presence of transitions in the dynamics underlying the solar activity. Besides it also shows and quantifies the different nature of these two solar indices. Furthermore, in order to check whether our results are affected by dataartefacts, we have also applied the RQA to both the recently recalibrated SSN series and the previous one, unveiling the main differences between the two data sets. The results are discussed in light of the recent literature on the subject.

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“…However regular high-quality data exist since 1970s (Livingston et al 1976) and thus cover essentially the same period as direct TSI measurements. Besides magnetograms, there are several disc-integrated chromospheric indices (Ermolli et al 2015) that can provide information on facular regions and have been used by various models, such as the 10. Bertello et al 2017).…”

Section: An Overviewmentioning

confidence: 99%

Long-term changes in solar activity and irradiance

Chatzistergos¹,

Krivova²,

Yeo³

2023

Preprint

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The Sun is the main energy source to Earth, and understanding its variability is of direct relevance to climate studies. Measurements of total solar irradiance (TSI) exist since 1978, but this is too short compared to climate-relevant time scales. Coming from a number of different instruments, these measurements require a cross-calibration, which is not straightforward, and thus several composite records have been created. All of them suggest a marginally decreasing trend since 1996. Most composites also feature a weak decrease over the entire period of observations, which is also seen in observations of the solar surface magnetic field and is further supported by Ca ii K data. Some inconsistencies, however, remain and overall the magnitude and even the presence of the long-term trend remain uncertain. Different models have been developed, which are used to understand the irradiance variability over the satellite period and to extend the records of solar irradiance back in time. Differing in their methodologies, all models require proxies of solar magnetic activity as input. The most widely used proxies are sunspot records and cosmogenic isotope data on centennial and millennial time scale, respectively. None of this, however, offers a sufficiently good, independent description of the long-term evolution of faculae and network responsible for solar brightening. This leads to significant uncertainties in the amplitude of the long-term changes in solar irradiance. Here we review recent efforts to improve irradiance reconstructions on time scales longer than the solar cycle and to reduce the existing uncertainty in the magnitude of the long-term variability. In particular, we highlight the potential of using 3D magnetohydrodynamical simulations of the solar atmosphere as input to more physical irradiance models and of historical full-disc Ca ii K observations encrypting direct facular information back to 1892.

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Solar Cycle Indices from the Photosphere to the Corona: Measurements and Underlying Physics

Cited by 4 publications

References 138 publications

Full-disc Ca ii K observations—A window to past solar magnetism

Full-disc Ca ii K observations—A window to past solar magnetism

Recurrence quantification analysis of two solar cycle indices

Long-term changes in solar activity and irradiance

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