Time-integrated energy budget of a solar activity complex

Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.

doi:10.1038/319654a0

Cited by 29 publications

(6 citation statements)

References 9 publications

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“…the energetic flux emitted by the Sun, integrated over the whole wavelength range as observed from space, and measured at 1 AU) varies about 0.10% in phase with magnetic activity (Fröhlich 1994). Superposed on this 11-year trend there are variations on shorter times scales (hours and days) that are found to be wholly due to the presence of active regions (ARs) (Sofia et al 1982;Chapman et al 1986). Spots, faculae and enhanced network are the cause of a large part of the observed variations over magnetic cycle time-scales (Willson & Hudson 1991;Krivova et al 2003), but the existence of a variation in the quiet photosphere component is still debated (Lydon et al 1996;.…”

Section: Introductionmentioning

confidence: 99%

Modeling the cyclic modulation of photospheric lines

Penza

Pietropaolo

Livingston

2006

A&A

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We have studied the behavior of three photospheric lines (Fe I 537.9, C I 538.0 and Ti II 538.1 nm), which have been monitored on the Sun for more than twenty years, either as full-disk or as center-disk measurements (Gray & Livingston 1997;Livingston & Wallace 2003). The aim is to detect a possible photospheric variation with the cycle. We try to reconstruct the cyclic variations of full-disk line depths as due to active region (AR) modulation through a spectral synthesis with FAL semi-empirical models (Fontenla et al. 1999) weighted by AR coverage factors. The sensitivity of these lines to thermodynamic variations and to AR presence is analyzed. We show that the AR modulation alone cannot explain all the observational results, either in amplitude or in phase. The "residual", i.e. the difference between observed behavior of these three lines at full-disk and that predicted by models for the AR modulation, results in a signal that is correlated with the measured center-disk line variations, and should be free from magnetic effects. Both the full-disk and the center-disk data show several periodicities; furthermore there are two periodicities shared by the three lines, one close to the 11 yr magnetic cycle and the other of 2.8 yr.

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Section: Introductionmentioning

confidence: 99%

Modeling the cyclic modulation of photospheric lines

Penza

Pietropaolo

Livingston

2006

A&A

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“…This spectral dependence can be exploited in order to distinguish the different mechanisms contributing to the TSI variation. In fact, while there is no doubt that the largest part of the TSI variations on the shorter time-scales are associated with the spatial and temporal distribution of the active regions (Willson et al 1981;Sofia et al 1982;Foukal & Lean 1986;Chapman et al 1986), the origin of the irradiance variations over magnetic cycle time-scales is still an open topic.…”

Section: Introductionmentioning

confidence: 99%

The sensitivity of the C I 538.0 nm Fe I 537.9 nm and Ti II 538.1 nm lines to solar active regions

Penza¹,

Caccin²,

Moro³

2004

A&A

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Abstract. Using spectroscopy to probe stellar global parameters, such as effective temperature, is much exploited in the literature. In the solar case it can be used as an indicator of magnetic cycle variations. In this work we study the sensitivity to bright active regions of three photospheric lines (Fe I 537.9 nm, C I 538.0 nm and Ti II 538.1 nm), which have been monitored on the sun for more than twenty years. In our analysis we compare our experimental results, from observations with the THEMIS telescope, with theoretical results, obtained by spectral synthesis with FAL semi empirical models (Fontenla et al. 1999, ApJ, 518, 480). We demonstrate the inappropriateness of using these lines (full disk integrated) as indicators of quiet sun irradiance modifications without considering their intrinsic variations due to active regions. Instead, their different sensitivity to the presence of active regions can be exploited in order to discriminate the background quiet sun variations from the magnetic region contributions.

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“…Seykora (1985) uses low amplitude, high frequency chopping to detect tiny intensity variations. Rosch and Yerle (1984), Hirayama et al (1985a), Dicke et al (1986) and Herzog et al (1986) scan parallel to the solar limb to measure facular contrast and image geometry. Limb-to-limb scanning is employed by .…”

Section: B Spectro-and Differential Photometrymentioning

confidence: 99%

VI. The Sun as a Star

Cram¹

1988

Trans. Int. Astron. Union

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Studies of the global (spatially unresolved) output from the sun are important for two main reasons: (1) the global solar output directed towards the earth plays a central role in solar-terrestrial relations, and (2) global solar observations form a link between (neccessarily) global observations of stars and the more refined spatially resolved observations which are available for the sun. This report covers both aspects (insofar as they concern the sun), using the time-scales of various phenomena as a basic distinguishing characteristic. Note that certain studies of spatially unresolved solar output have not been discussed, since they are actually directed toward the investigation of phenomena of strictly limited spatial extent [e.g. radiospectrograph observations (e.g. Wiehl et al. 1985) and studies of X-ray bursts (e.g. Thomas et al. 1985)]. Collections of relevant papers may be found in De Jager and Svestka (1985) and Labonte et al. (1984), while a review of germane stellar work is available in Baliunas and Vaughan (1985) and solar-terrestrial work in Donnelly and Heath (1985). A comprehensive summary of the subject by Hudson will appear soon in Review of Geophysics and Planetary Physics.

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Time-integrated energy budget of a solar activity complex

Cited by 29 publications

References 9 publications

Modeling the cyclic modulation of photospheric lines

Modeling the cyclic modulation of photospheric lines

The sensitivity of the C I 538.0 nm Fe I 537.9 nm and Ti II 538.1 nm lines to solar active regions

VI. The Sun as a Star

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