Mechanisms for total and spectral solar irradiance variations

Haberreiter, M.

doi:10.1017/s1743921309992687

Cited by 3 publications

(4 citation statements)

References 43 publications

(38 reference statements)

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“…Most of the chromospheric emission lines formed at temperatures below 2 × 10 4 K are emitted by chromospheric ions (Doschek et al 1977). The main chromospheric emission lines for the 0.5 nm wavelength interval in the range 200.5 nm -300.5 nm are C II, Co II, Cr II, Fe II, Mg II h&k line, Mn II, Ni II and Ti II, and all these emission lines are a function of wavelength (Haberreiter 2010).…”

Section: Data Analysis Resultsmentioning

confidence: 96%

Solar spectral irradiance variability of some chromospheric emission lines through the solar activity cycles 21-23

2017

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A study of variations of solar spectral irradiance (SSI) in the wavelength ranges 121.5 nm-300.5 nm for the period 1981-2009 is presented. We used various data for ultraviolet (UV) spectral lines and international sunspot number (ISSN) from interactive data centers such as SME (NSSDC), UARS (GDAAC), SORCE (LISIRD) and SIDC, respectively. We reduced these data by using the MATLAB software package. In this respect, we revealed negative correlations of intensities of UV (289.5 nm-300.5 nm) spectral lines originating in the solar chromosphere with the ISSN index during the unusually prolonged minimum between the solar activity cycles (SACs) 23 and 24. We also compared our results with the variations of solar activity indices obtained by the ground-based telescopes. Therefore, we found that plage regions decrease while facular areas are increasing in SAC 23. However, the decrease in plage regions is seen in small sunspot groups (SGs), contrary to this, these regions in large SGs are comparable to previous SACs or even larger as is also seen in facular areas. Nevertheless, negative correlations between ISSN and SSI data indicate that these variations are in close connection with the classes of sunspots/SGs, faculae and plage regions. Finally, we applied the time series analysis of spectral lines corresponding to the wavelengths 121.5 nm-300.5 nm and made comparisons with the ISSN data. We found an unexpected increase in the 298.5 nm line for the Fe II ion. The variability of Fe II ion 298.5 nm line is in close connection with the facular areas and plage regions, and the sizes of these solar surface indices play an important role for the SSI variability, as well. So, we compared the connection between the sizes of faculae and plage regions, sunspots/SGs, chemical elements and SSI variability. Our future work will be the theoretical study of this connection and developing of a corresponding model.

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Section: Data Analysis Resultsmentioning

confidence: 96%

Solar spectral irradiance variability of some chromospheric emission lines through the solar activity cycles 21-23

2017

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“…A range of other spectral activity indicators have also been explored and found useful as tracers of chromospheric magnetic activity (see Figure 6), flares and plages, including Hα [4,110] and Hβ emission [111], He I D 3 (587.59 nm) and 1.08 µm absorption [112][113][114][115], the Na I D 1 and D 2 lines, the infrared Ca II triplet absorption lines (centred at 8498.062 Å, 8542.144 Å and 8662.170 Å), and extreme ultraviolet (UV; 200.5-300.5 nm) resonance lines associated with surface effective temperatures T eff < 2 × 10 4 K, including C I, C II, Co II, Cr II, Fe II, Mn II, Ni II, O I, Si II and Ti II [116], as well as Mg II h and k [117][118][119]. Of these, Fe II (298.5 nm) is the dominant contributor to solar irradiance variations in high-ionisation environments [114].…”

Section: Spectroscopic Diagnosticsmentioning

confidence: 99%

Stellar Chromospheric Variability

Grijs

Kamath

2021

Universe

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Cool stars with convective envelopes of spectral types F and later tend to exhibit magnetic activity throughout their atmospheres. The presence of strong and variable magnetic fields is evidenced by photospheric starspots, chromospheric plages and coronal flares, as well as by strong Ca ii H+K and Hα emission, combined with the presence of ultraviolet resonance lines. We review the drivers of stellar chromospheric activity and the resulting physical parameters implied by the observational diagnostics. At a basic level, we explore the importance of stellar dynamos and their activity cycles for a range of stellar types across the Hertzsprung–Russell diagram. We focus, in particular, on recent developments pertaining to stellar rotation properties, including the putative Vaughan–Preston gap. We also pay specific attention to magnetic variability associated with close binary systems, including RS Canum Venaticorum, BY Draconis, W Ursae Majoris and Algol binaries. At the present time, large-scale photometric and spectroscopic surveys are becoming generally available, thus leading to a resurgence of research into chromospheric activity. This opens up promising prospects to gain a much improved understanding of chromospheric physics and its wide-ranging impact.

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“…The second is daily sunspot area of the full Sun. Sunspot area is sometimes used to represent "the sunspots blocking" [11,37], which can be downloaded from NASA (https://solarscience.msfc.nasa.gov/greenwch.shtml). The third is Mg II core-to-wing ratio, called Mg II index in this study, which is a robust measure of chromospheric activity [38][39][40].…”

Section: The Reason For the Solar Cycle Variation Of Tsimentioning

confidence: 99%

“…The variability of the photosphere (wings) is quite small, while the chromospheric activity causes about 30% variations of the core. Because the core-to-wing ratio is not easily affected by the instruments, Mg II index which is used to represent "the intensification due to bright faculae, plages, and network elements" is very reliable [11,37,38]. The Mg II index composite can be downloaded from the website http://www .iup.uni-bremen.de/gome/gomemgii.html.…”

Section: The Reason For the Solar Cycle Variation Of Tsimentioning

confidence: 99%

Revisiting the Question: The Cause of the Solar Cycle Variation of Total Solar Irradiance

Xiang

2019

Advances in Astronomy

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The Mg II index and sunspot area are usually used to represent the intensification contribution by solar bright structures to total solar irradiance (TSI) and sunspot darkening, respectively. In order to understand the cause of the solar cycle variation of TSI, we use extension of wavelet transform, wavelet coherence (WTC), and partial wavelet coherence (PWC), to revisit this issue. The WTC of TSI with sunspot area shows that the two time series are very coherent on timescales of one solar cycle, but the PWC of TSI with sunspot area, which can find the results of WTC after eliminating the effect of the Mg II index, indicates that the solar cycle variation of TSI is not related to sunspots on the solar surface. The coherence of two time series at these timescales should be due to a particular phase relation between sunspots and TSI. The WTC and PWC of TSI with Mg II index show that the solar cycle variation of TSI is highly related to Mg II index, which reflects the relation of TSI with the long-term part of Mg II index that shows the intensification contribution by the small magnetic features to TSI. Consequently, the solar cycle variation of TSI is dominated by the small magnetic features on the solar full disk. Additionally, we also show the combined effects of the sunspot darkening and the intensification contribution represented by Mg II index to TSI on timescales of a few days to several months and indicate that the faculae increase TSI and contribute to its variation at these timescales.

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Mechanisms for total and spectral solar irradiance variations

Cited by 3 publications

References 43 publications

Solar spectral irradiance variability of some chromospheric emission lines through the solar activity cycles 21-23

Solar spectral irradiance variability of some chromospheric emission lines through the solar activity cycles 21-23

Stellar Chromospheric Variability

Revisiting the Question: The Cause of the Solar Cycle Variation of Total Solar Irradiance

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