Long-Term Periodicity Variations of the Solar Radius

Qu, Zhining; Xie, J. L.

doi:10.1088/0004-637x/762/1/23

Cited by 23 publications

(15 citation statements)

References 39 publications

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“…Earlier work by Laclare et al (1996) showed the opposite behavior; the solar radius was smaller when more spots were present, at least for more than 1.5 solar cycles between 1978 and 1994. Using the same dataset as Laclare et al (1996), but extended to the year 2000, Qu & Xie (2013) came to the same conclusion; the Sun shrinks when the activity is high, probably due to cyclic variation of the magnetic pressure in the solar convection zone. On the basis of the magnetic virial theorem, Stothers (2006) suggests that the solar radius changes by about 0.02% with the 11 yr cycle, and decreases around the maximum activity.…”

Section: Summary and Discussionmentioning

confidence: 64%

Magnitude-range brightness variations of overactive K giants

Oláh

Moór

Kővári

et al. 2014

A&A

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Context. Decades-long, phase-resolved photometry of overactive spotted cool stars has revealed that their long-term peak-to-peak light variations can be as large as one magnitude. Such brightness variations are too large to be solely explained by rotational modulation and/or a cyclic, or pseudo-cyclic, waxing and waning of surface spots and faculae as we see in the Sun. Aims. We study three representative, overactive spotted K giants (IL Hya, XX Tri, and DM UMa) known to exhibit V-band light variations between 0. m 65-1. m 05. Our aim is to find the origin of their large brightness variation. Methods. We employ long-term phase-resolved multicolor photometry, mostly from automatic telescopes, covering 42 yr for IL Hya, 28 yr for XX Tri, and 34 yr for DM UMa. For one target, IL Hya, we present a new Doppler image from NSO data taken in late 1996. Effective temperatures for our targets are determined from all well-sampled observing epochs and are based on a V − I C color-index calibration.Results. The effective temperature change between the extrema of the rotational modulation for IL Hya and XX Tri is in the range 50-200 K. The bolometric flux during maximum of the rotational modulation, i.e., the least spotted states, varied by up to 39% in IL Hya and up to 54% in XX Tri over the course of our observations. We emphasize that for IL Hya it is just about half of the total luminosity variation that can be explained by the photospheric temperature (spots/faculae) changes, while for XX Tri it is even about one third. The long-term, 0. m 6 V-band variation of DM UMa is more difficult to explain because little or no B − V color index change is observed on the same timescale. Placing the three stars with their light and color variations into H-R diagrams, we find that their overall luminosities are generally too low compared to predictions from current evolutionary tracks. Conclusions. A change in the stellar radius due to strong and variable magnetic fields during activity cycles likely plays a role in explaining the anomalous brightness and luminosity of our three targets. At least for IL Hya, a radius change of about 9% is suggested from m bol and T eff , and is supported by independent v sin i measurements.

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Section: Summary and Discussionmentioning

confidence: 64%

Magnitude-range brightness variations of overactive K giants

Oláh

Moór

Kővári

et al. 2014

A&A

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“…Visual inspection suggests that the time series for temperature and aggregate forcing embody cyclical behavior. To remove these cyclical components, we use equation (1) to fit a periodic sinusoid function that accounts for three prominent solar cycles: the eleven year Schwabe cycle (see for example Qu and Xie, 2013), the twenty-two year Hale cycle (see for example Mursula et al, 2001) and the century-long Gleissberg cycle (see for example Ogurtsov et al, 2002):…”

Section: Preliminary Analysis and Unit Root Testingmentioning

confidence: 99%

Long-Run Changes in Radiative Forcing and Surface Temperature: The Effect of Human Activity over the Last Five Centuries

2015

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We test two hypotheses that are derived from the anthropogenic theory of climate change. The first postulates that a growing population and increasing economic activity increase anthropogenic emissions of radiatively active gases relative to natural sources and sinks, and this alters global biogeochemical cycles in a way that increases the persistence of radiative forcing and temperature. The second postulates that the increase in the persistence of radiative forcing transmits a stochastic trend to the time series for temperature. Results indicate that the persistence of radiative forcing and temperature changes from I(0) to I(1) during the last 500 years and that the I(1) fingerprint in radiative forcing can be detected in a statistically measureable fashion in surface temperature. As such, our results are consistent with the physical mechanisms that underlie the theory of anthropogenic climate change.

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“…The key to these findings is that the solar radius has been demonstrated to vary within rotation cycles (Moussaoui et al 2001;Penna et al 2002;Kiliç & Golbasi 2011) and an 11-year period (Laclare et al 1996;Moussaoui et al 2001;Qu & Xie 2013). Laclare et al (1996), Moussaoui et al (2001), Reis Neto et al (2003), Kiliç et al (2009) and Qu & Xie (2013) found that the solar radius displays some mid-term periods (0.3-6 years). However, regarding the phase relation between long-term variation of the solar radius and solar activity, evidence is inconclusive.…”

Section: Introductionmentioning

confidence: 94%

Periodicity of the solar radius revisited by using empirical mode decomposition and the Lomb–Scargle method

Wen

2015

Res. Astron. Astrophys.

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Using the Hilbert-Huang transform and the Lomb-Scargle method, we investigate periodicities in the daily solar radius data during the time interval from February 1978 to October 1999 derived from Calern Observatory. The following prominent periods are found: (1) the rotation cycle signal; (2) several mid-term periods including 122, 162.9 and 225 days, annual-variation periodicities (319 and 359 days), quasi-triennial oscillations (3.46 and 3.94 years); (3) the 11-year Schwabe cycle, which is in anti-phase with solar activity. This result indicates that the strong magnetic field associated with the Sun has a greater inhibitive effect on the radius variation.

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Long-Term Periodicity Variations of the Solar Radius

Cited by 23 publications

References 39 publications

Magnitude-range brightness variations of overactive K giants

Magnitude-range brightness variations of overactive K giants

Long-Run Changes in Radiative Forcing and Surface Temperature: The Effect of Human Activity over the Last Five Centuries

Periodicity of the solar radius revisited by using empirical mode decomposition and the Lomb–Scargle method

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