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Fröhlich, C.; Crommelynck, D.; Wehrli, Christoph; Anklin, Martin; Dewitte, Steven; Fichot, Alain; Finsterle, W.; Jiménez, Antonio; Chevalier, André; Roth, Hansjörg

doi:10.1023/a:1004929108864

Cited by 124 publications

(66 citation statements)

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“…The VIRGO data from 18 Jan. 1996 until 31 Mar. 2009 (Fröhlich et al 1997) used here are from V6.2, which has been updated from V6.1 used earlier by Fröhlich (2008). The difference between these two versions is important and related to the way corrections are applied to PM6V-B, one of the reference radiometer of VIRGO.…”

Section: Datamentioning

confidence: 99%

Evidence of a long-term trend in total solar irradiance

Fröhlich¹

2009

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Aims. During the solar minimum of 2008, the value of total solar irradiance at 1 AU (TSI) was more than 0.2 Wm −2 lower than during the last minimum in 1996, indicating for the first time a directly observed long-term change. On the other hand, chromospheric indices and hence solar UV irradiance do not exhibit a similar change. Methods. Comparison of TSI with other activity parameters indicates that only the open solar magnetic field, B R , observed from satellites at 1 AU show a similar long-term behaviour. The values at the minima correlate well and the linear fit provides a direct physical relationship between TSI and B R during the minimum times.Results. This correlation allows an unambiguous reconstruction of TSI back in time, provided the open solar magnetic field can be determined from e.g. geomagnetic indices or cosmogenic radionucleides. Since the solar UV irradiance has no long-term trend, the mechanism for the secular change of TSI must differ from the effect of surface magnetism, as manifested by sunspots, faculae, and network which indeed explain well the intra-cycle variability of both total and spectral irradiance. Conclusions. The long-term trend of TSI is most probably caused by a global temperature change of the Sun that does not influence the UV irradiance in the same way as the surface magnetic fields.

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Section: Datamentioning

confidence: 99%

Evidence of a long-term trend in total solar irradiance

Fröhlich¹

2009

A&A

205

200

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“…For the period 1996 to the present day the PMOD composite is mainly based on TSI measured with the VIRGO instrument (Fröhlich et al 1997) on-board the Solar Heliospheric Observatory (SOHO). Because VIRGO has been in space over a relative long period, the observed drop in the TSI could be due to aging of the VIRGO instrument.…”

Section: Introductionmentioning

confidence: 99%

Total solar irradiance since 1996: is there a long-term variation unrelated to solar surface magnetic phenomena?

Steinhilber

2010

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“…The "SOlar VAriability" (SOVA) experiment on board the EUropean REtrievable CArrier (EURECA, July 31, 1992 to June 1993), consisted of two different types of absolute radiometers, the "Differential Dual Absolute Radiometer" (DIARAD) and the PMO-6 type of absolute radiometer (Crommelynck et al 1994;Romero et al 1994). The "Variability of solar IRradiance and Gravity Oscillations" (VIRGO) experiment on the SOlar Heliospheric Observatory (SOHO) carried two radiometers (DIARAD and PMO6-V) and provided another important segment of the long-term total irradiance data base since January 1996 (Fröhlich et al 1997). Based on the Nimbus-7/ERB, SMM/ACRIM I, UARS/ACRIM II, and SOHO/VIRGO measurements, Fröhlich & Lean (1998) compiled a "composite" total irradiance, taking into account all possible corrections for the measurements.…”

Section: Description Of the Total Irradiance Measurementsmentioning

confidence: 99%

“…Short-term variations on time scales of days to months are directly related to the evolution of active regions via the combined effect of sunspots and faculae (Willson et al 1981;Chapman 1987;Fröhlich & Pap 1989). On time scales of minutes to hours, the effect of granulation, meso-and super-granulation is seen in the total irradiance, whereas in the 5-minute range the p-modes cause rapid irradiance fluctuations (Fröhlich et al 1997).…”

Section: Description Of the Total Irradiance Measurementsmentioning

confidence: 99%

“…It has been shown that empirical models of total irradiance, solely based on the surface manifestations of solar magnetic activity, cannot explain all the aspects of irradiance changes (Fröhlich & Pap 1989;Kuhn 1996;Fröhlich et al 1997;Wehrli 1992). Identification of the causes of the residual variability in Fig.…”

Section: Description Of the Total Irradiance Measurementsmentioning

confidence: 99%

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On the relation between total irradiance and radius variations

Pap

Rozelot²,

Godier³

et al. 2001

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Abstract. We use Singular Spectrum Analysis (SSA) to analyze total solar irradiance variations and CERGA radius measurements. Total solar irradiance has been monitored from space for more than two decades, whilst ground-based radius measurements are available as a coherent time series from 1975. We compare these indicators to try to understand the origin of energy production inside the Sun. One of the main objectives was to assess the reality of the observed variations of the Sun's radius by distinguishing the signal from the noise. Two approaches were used: one using SSA on ground-based data averaged over 90 days, in order to smooth the signal (especially over periods when no data were obtained, mainly in winter time); the second repeats the analysis on individual measurements corrected by reporting data to the zenith. As expected, the level of noise is higher in the first case and the reconstructed noise level, which is large, indicates the difficulty in ascertaining the solar origin in the apparent variability of the solar radius. It is shown from the reconstructed components that the main variation in amplitude (over 930 days) is pronounced during the first part of the measurements and seems to disappear after 1988. There is also a variation with a periodicity of 1380 days, of lower amplitude than that of the shorter component. In both cases, these variations disappear during the rising portion of cycle 23. The first reconstructed component shows that total irradiance varies in parallel with the solar cycle, being higher during maximum activity conditions. The reconstructed radius trend indicates that the solar radius was higher during the minimum of solar cycle 21, but its decrease with the rising activity of cycle 23 is less obvious. The observed value of the solar radius increased by about 0.11 arcsec from the maximum of cycle 21 to the minimum between cycles 21 and 22. Most importantly, we report a long-term radius variation which increased from the maximum of cycle 21 to minimum by about 0.015%, while a smaller decrease (around 0.01%) is seen from the minimum of cycle 21 to the maximum of cycle 22. This study indicates need for measurements of the degree of the radius changes taken from space, together with total irradiance measurements to establish the phase relation between these two quantities.

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Cited by 124 publications

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Evidence of a long-term trend in total solar irradiance

Evidence of a long-term trend in total solar irradiance

Total solar irradiance since 1996: is there a long-term variation unrelated to solar surface magnetic phenomena?

On the relation between total irradiance and radius variations

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