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

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
N. B. Xiang
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Solar Irradiance ◽  
Total Solar Irradiance ◽  
Sunspot Area ◽  
Wavelet Coherence ◽  
Solar Cycle Variation ◽  
Cycle Variation ◽  
Magnetic Features

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.

scholarly journals Solar Cycle Variation in Solar Irradiance

2014 ◽  
Vol 186 (1-4) ◽  
pp. 137-167 ◽  
Author(s):  
K. L. Yeo ◽  
N. A. Krivova ◽  
S. K. Solanki
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Solar Cycle Variation ◽  
Cycle Variation

scholarly journals Modelling solar irradiance from ground-based photometric observations

2020 ◽  
Vol 10 ◽  
pp. 45 ◽  
Author(s):  
Theodosios Chatzistergos ◽  
Ilaria Ermolli ◽  
Fabrizio Giorgi ◽  
Natalie A. Krivova ◽  
Cosmin Constantin Puiu
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Total Solar Irradiance ◽  
Visible Range ◽  
Solar Cycles ◽  
Term Trend ◽  
Photometric Observations ◽  
San Fernando ◽  
Long Term Trend

Total solar irradiance (TSI) has been monitored from space since 1978, i.e. for about four solar cycles. The measurements show a prominent variability in phase with the solar cycle, as well as fluctuations on timescales shorter than a few days. However, the measurements were done by multiple and usually relatively short-lived missions. The different absolute calibrations of the individual instruments and the unaccounted for instrumental trends make estimates of the possible long-term trend in the TSI highly uncertain. Furthermore, both the variability and the uncertainty are strongly wavelength-dependent. While the variability in the UV irradiance is clearly in-phase with the solar cycle, the phase of the variability in the visible range has been debated. In this paper, we aim at getting an insight into the long-term trend of TSI since 1996 and the phase of the solar irradiance variations in the visible part of the spectrum. We use independent ground-based full-disc photometric observations in Ca II K and continuum from the Rome and San Fernando observatories to compute the TSI since 1996. We follow the empirical San Fernando approach based on the photometric sum index. We find a weak declining trend in the TSI of $ {-7.8}_{-0.8}^{+4.9}\times 1{0}^{-3}$ Wm−2 y−1 between the 1996 and 2008 activity minima, while between 2008 and 2019 the reconstructed TSI shows no trend to a marginally decreasing (but statistically insignificant) trend of $ {-0.1}_{-0.02}^{+0.25}\times 1{0}^{-3}$ Wm−2 y−1. The reference TSI series used for the reconstruction does not significantly affect the determined trend. The variation in the blue continuum (409.2 nm) is rather flat, while the variation in the red continuum (607.1 nm) is marginally in anti-phase, although this result is extremely sensitive to the accurate assessment of the quiet Sun level in the images. These results provide further insights into the long-term variation of the TSI. The amplitude of the variations in the visible is below the uncertainties of the processing, which prevents an assessment of the phase of the variations.

scholarly journals Digitized archive of the Kodaikanal images: Representative results of solar cycle variation from sunspot area determination

2013 ◽  
Vol 550 ◽  
pp. A19 ◽  
Author(s):  
B. Ravindra ◽  
T. G. Priya ◽  
K. Amareswari ◽  
M. Priyal ◽  
A. A. Nazia ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Sunspot Area ◽  
Solar Cycle Variation ◽  
Cycle Variation ◽  
Area Determination

Long-term and solar cycle variation of the ring current

1996 ◽  
Vol 101 (A11) ◽  
pp. 24727-24735 ◽  
Author(s):  
S. Vennerstrøm ◽  
E. Friis-Christensen
Keyword(s):  
Solar Cycle ◽  
Ring Current ◽  
Solar Cycle Variation ◽  
Cycle Variation
Sign in / Sign up

Export Citation Format

Share Document