Time‐frequency analysis of total solar irradiance variations

Willson, R. C.; Мордвинов, А. В.

doi:10.1029/1999gl010700

Cited by 22 publications

(13 citation statements)

References 14 publications

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“…associated to the active regions located opposite each other in solar longitude. The solar periodicities issued from the present analysis are in close agreement with those obtained by different authors, on the basis of different procedures for the treatment of the total solar irradiance (e.g., Willson (1997); Willson & Mordvinov (1999); Fröhlich & Lean (1998)).…”

Section: The Sunsupporting

confidence: 90%

Wavelets: a powerful tool for studying rotation, activity, and pulsation inKeplerand CoRoT stellar light curves

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Roque

Estrela

et al. 2014

A&A

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Aims. The wavelet transform has been used as a powerful tool for treating several problems in astrophysics. In this work, we show that the time-frequency analysis of stellar light curves using the wavelet transform is a practical tool for identifying rotation, magnetic activity, and pulsation signatures. We present the wavelet spectral composition and multiscale variations of the time series for four classes of stars: targets dominated by magnetic activity, stars with transiting planets, those with binary transits, and pulsating stars. Methods. We applied the Morlet wavelet (6th order), which offers high time and frequency resolution. By applying the wavelet transform to the signal, we obtain the wavelet local and global power spectra. The first is interpreted as energy distribution of the signal in time-frequency space, and the second is obtained by time integration of the local map. Results. Since the wavelet transform is a useful mathematical tool for nonstationary signals, this technique applied to Kepler and CoRoT light curves allows us to clearly identify particular signatures for different phenomena. In particular, patterns were identified for the temporal evolution of the rotation period and other periodicity due to active regions affecting these light curves. In addition, a beat-pattern signature in the local wavelet map of pulsating stars over the entire time span was also detected.

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Section: The Sunsupporting

confidence: 90%

Wavelets: a powerful tool for studying rotation, activity, and pulsation inKeplerand CoRoT stellar light curves

Bravo

Roque

Estrela

et al. 2014

A&A

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“…In the model with the overcritical α effect, we find the opposite situation. The solar observations show the increasing luminosity during the maximum of the solar cycles [87]. The variation of the photometric brightness of solar-type stars tends to inverse the sign with the increasing level of the magnetic activity [90].…”

Section: Discussionmentioning

confidence: 99%

Nonkinematic solar dynamo models with double-cell meridional circulation

Пипин

2018

Journal of Atmospheric and Solar-Terrestrial Physics

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Employing the standard solar interior model as input we construct a dynamically-consistent nonlinear dynamo model that takes into account the detailed description of the Λ-effect, turbulent pumping, magnetic helicity balance, and magnetic feedback on the differential rotation and meridional circulation. The background mean-field hydrodynamic model of the solar convection zone accounts the solar-like angular velocity profile and the double-cell meridional circulation. We investigate an impact of the nonlinear magnetic field generation effects on the long-term variability and properties of the magnetic cycle. The nonlinear dynamo solutions are studied in the wide interval of the α effect parameter from a slightly subcritical to supercritical values. It is found that the magnetic cycle period decreases with the increasing cycle's magnitude. The periodic long-term variations of the magnetic cycle are excited in case of the overcritical α effect. These variations result from the hemispheric magnetic helicity exchange. It depends on the magnetic diffusivity parameter and the magnetic helicity production rate. The large-scale magnetic activity modifies the distribution of the differential rotation and meridional circulation inside convection zone. It is found that the magnetic feedback on the global flow affects the properties of the long-term magnetic cycles. We confront our findings with solar and stellar magnetic activity observations.

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“…TSI deficits and excesses of sunspot and facular area on the solar rotational time scale cause the highest frequency variations. [ Willson et al , 1981; Willson and Mordvinov , 1999]. Broad peaks around 1980, 1991 and 2001 correspond to periods of maximum solar magnetic activity during solar cycles 21, 22 and 23.…”

Section: The Acrim Composite Tsi Time Seriesmentioning

confidence: 99%

Secular total solar irradiance trend during solar cycles 21–23

Willson

Мордвинов

2003

Geophysical Research Letters

Self Cite

311

248

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[1] A series of satellite total solar irradiance (TSI) observations can be combined in a precise solar magnetic cycle length composite TSI database by determining the relationship between two non-overlapping components: ACRIM1 and ACRIM2. [Willson and Hudson, 1991;Willson, 1994] An ACRIM composite TSI time series using the Nimbus7/ERB results [Hoyt et al., 1992] to relate ACRIM1 and ACRIM2 demonstrates a secular upward trend of 0.05 percent-per-decade between consecutive solar activity minima. [Willson, 1997] A PMOD TSI composite using ERBS [Lee et al., 1995] comparisons to relate ACRIM1 and ACRIM2 [Fröhlich and Lean, 1998] differs from the ACRIM composite in two significant respects: a negligible trend between solar minima and lower TSI at solar maxima. Our findings indicate the lower PMOD trend and lower PMOD TSI at the maxima of solar cycles 22 and 23 are artifacts of ERBS degradation. Lower PMOD TSI during the maximum of cycle 21 results from modifications of Nimbus7/ERB and ACRIM1 published results that produces better agreement with a TSI/solar proxy model [Foukal and Lean, 1988;Lean et al., 1995; Frö hlich and Lean, 1998].

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Time‐frequency analysis of total solar irradiance variations

Abstract: Abstract.Continuous

Cited by 22 publications

References 14 publications

Wavelets: a powerful tool for studying rotation, activity, and pulsation inKeplerand CoRoT stellar light curves

Wavelets: a powerful tool for studying rotation, activity, and pulsation inKeplerand CoRoT stellar light curves

Nonkinematic solar dynamo models with double-cell meridional circulation

Secular total solar irradiance trend during solar cycles 21–23

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