共查询到20条相似文献，搜索用时 31 毫秒
1.
Richard C. Willson 《Astrophysics and Space Science》2014,352(2):341-352
The effects of scattering and diffraction on the observations of the ACRIMSAT/ACRIM3 satellite TSI monitoring mission have been characterized by the preflight calibration approach for satellite total solar irradiance (TSI) sensors implemented at the LASP/TRF (Laboratory for Atmospheric and Space Physics/Total Solar Irradiance Radiometer Facility). The TRF also calibrates the SI (International System of units) traceability to the NIST (National Institute of Standards and Technology) cryo-radiometric scale. ACRIM3’s self-calibration agrees with NIST to within the uncertainty of the test procedure (～500 ppm). A correction of ～5000 ppm was found for scattering and diffraction that has significantly reduced the scale difference between the results of the ACRIMSAT/ACRIM3 and SORCE/TIM satellite experiments. Algorithm updates reflecting more than 10 years of mission experience have been made that further improve the ACRIM3 results by eliminating some thermally driven signal and increasing the signal to noise ratio. The result of these changes is a more precise and detailed picture of TSI variability. Comparison of the results from the ACRIM3, SORCE/TIM and SOHO/VIRGO satellite experiments demonstrate the near identical detection of TSI variability on all sub-annual temporal and amplitude scales during the TIM mission. The largest occurs at the rotational period of the primary solar activity longitudes. On the decadal timescale, while ACRIM3 and VIRGO results exhibit close agreement throughout, TIM exhibits a consistent 500 ppm upward trend relative to ACRIM3 and VIRGO. A solar magnetic activity area proxy for TSI has been used to demonstrate that the ACRIM TSI composite and its +0.037 %/decade TSI trend during solar cycles 21–23 is the most likely correct representation of the extant satellite TSI database. The occurrence of this trend during the last decades of the 20th century supports a more robust contribution of TSI variation to detected global temperature increase during this period than predicted by current climate models. 相似文献
2.
We model total solar irradiance (TSI) using photometric irradiance indices from the San Fernando Observatory (SFO), and compare our model with measurements compiled from different space-based radiometers. Space-based measurements of TSI have been obtained recently from ACRIM-3 on board the ACRIMSAT. These data have been combined with other data sets to create an ACRIM-based composite. From VIRGO on board the Solar and Heliospheric Observatory (SOHO) spacecraft two different TSI composites have been developed. The VIRGO irradiance data have been combined by the Davos group to create a composite often referred to as PMOD (Physikalisch-Meteorologisches Observatorium Davos). Also using data from VIRGO, the Royal Meteorological Institute of Belgium (RMIB) has created a separate composite TSI referred to here as the RMIB composite. We also report on comparisons with TSI data from the Total Irradiance Monitor (TIM) experiment on board the Solar Radiation and Climate Experiment (SORCE) spacecraft. The SFO model correlates well with all four experiments during the seven-year SORCE interval. For this interval, the squared correlation coefficient R 2 was 0.949 for SORCE, 0.887 for ACRIM, 0.922 for PMOD, and 0.924 for RMIB. Long-term differences between the PMOD, ACRIM, and RMIB composites become apparent when we examine a 21.5-year interval. We demonstrate that ground-based photometry, by accurately removing TSI variations caused by solar activity, is useful for understanding the differences that exist between TSI measurements from different spacecraft experiments. 相似文献
3.
Solar empirical models based on regression of two variability indices for radiation from the photosphere and chromosphere
fit total solar irradiance (TSI) observations with accuracy comparable to the precision reported for the observations themselves.
However, the physical meaning of the fitting coefficients and their stability during different phases of the solar cycle has
not been examined in detail. We test the stability of the coefficients in regression models of the VIRGO TSI observations
over the nine years from the minimum of Cycle 23 in 1996 through the maximum to 2005. We also show how the coefficients converge
to the ‘`best fit’' using a search in the coefficient space. Analysis of TSI variability in different phases of this cycle
shows little change in regression models as long as the time periods used in the regression are long enough to show the slow
solar cycle variation in TSI. We extend our analysis to TSI observations from ERB, ACRIM2, ACRIM3, DIARAD, and TIM. The regression
models from these time series show large systematic differences in fitting coefficients for the plage and sunspot indices
that we used. These differences are significantly larger than the estimated uncertainties in the coefficients and point to
the difficulty of combining observations from different instruments to create an accurate composite TSI record over several
solar cycles. Our results clearly demonstrate the improvement in precision of TSI measurements from the Nimbus 7 ERB in Cycle
22 to the latest SORCE TIM data in Cycle 23. 相似文献
4.
The time series of total solar irradiance (TSI) satellite observations since 1978 provided by ACRIM and PMOD TSI composites are studied. We find empirical evidence for planetary-induced forcing and modulation of solar activity. Power spectra and direct data pattern analysis reveal a clear signature of the 1.09-year Earth-Jupiter conjunction cycle, in particular during solar cycle 23 maximum. This appears to suggest that the Jupiter side of the Sun is slightly brighter during solar maxima. The effect is observed when the Earth crosses the Sun-Jupiter conjunction line every 1.09 years. Multiple spectral peaks are observed in the TSI records that are coherent with known planetary harmonics such as the spring, orbital and synodic periods among Mercury, Venus, Earth and Jupiter: the Mercury-Venus spring-tidal cycle (0.20 year); the Mercury orbital cycle (0.24 year); the Venus-Jupiter spring-tidal cycle (0.32 year); the Venus-Mercury synodic cycle (0.40 year); the Venus-Jupiter synodic cycle (0.65 year); and the Venus-Earth spring tidal cycle (0.80 year). Strong evidence is also found for a 0.5-year TSI cycle that could be driven by the Earth’s crossing the solar equatorial plane twice a year and may indicate a latitudinal solar-luminosity asymmetry. Because both spring and synodic planetary cycles appear to be present and the amplitudes of their TSI signatures appear enhanced during sunspot cycle maxima, we conjecture that on annual and sub-annual scales both gravitational and electro-magnetic planet-sun interactions and internal non-linear feedbacks may be modulating solar activity. Gravitational tidal forces should mostly stress spring cycles while electro-magnetic forces could be linked to the solar wobbling dynamics, and would mostly stress the synodic cycles. The observed statistical coherence between the TSI records and the planetary harmonics is confirmed by three alternative tests. 相似文献
5.
We investigate the periodicity in the PMOD composite of the daily total solar irradiance (TSI) from 21 September 1978 to 9 June
2009. Besides the Schwabe cycle period (10.32 years), the quasi-rotation period is found to be statistically significant in
TSI, whose value is about 32 days, longer than that in sunspot activity (27 days), and it intermittently appears around the
sunspot maximum times. The quasi-rotation period in TSI is inferred to be mainly caused by sunspot activity, but to be modulated
by bright features as well. It was previously found that variations of TSI over a Schwabe solar cycle mainly come from the
combination of the sunspots’ blocking and the intensification due to bright faculae, plages, and network elements, with a
slight dominance of the bright-feature effect during the maximum of the Schwabe cycle. For the sunspot-blocking and the bright-feature
effect to contribute to TSI over a Schwabe solar cycle, the former is inferred to lead the latter by 29 days at least. 相似文献
6.
The He 1083 nm line equivalent width and the 10.7 cm radio flux are employed to model the total solar irradiance corrected for sunspot deficit. A new area dependent photometric sunspot index (APSI) based on sunspot photometry by Steinegger et al. (1990) is used to correct the irradiance data for sunspot deficits. Two periods of time are investigated: firstly, the 1980–1989 period between the maxima of solar cycles 21 and 22; this period is covered by ACRIM I irradiance data. Secondly, the 1978–92 period which includes both maxima; here, the revised Nimbus-7 ERB data are used.For both He 1083 nm and 10.7 cm radio flux irradiance models as well as ACRIM I and ERB irradiance data, the APSI yields an improved fit compared to the one obtained with the standard Photometric Sunspot Index (PSI) which uses a constant bolometric spot contrast. With APSI, the standard deviation calculated from daily values is 0.461 Wm–2 for the period 1980–89 modelling ACRIM I vs. He 1083 nm, as compared to 0.478 when PSI is used, and to 0.531 for the uncorrected ACRIM series. A similar improvement is obtained for the same period modelling ERB vs. He 1083 nm, while there is almost no improvement for the long period.As a general result the models provide a good fit with the spot-deficit.-corrected irradiance only during the period between the maxima. If both maxima are included (period 1978–92) the He 1083 nm and 10.7 cm radio flux models show appreciably larger discrepancies to the irradiances corrected for PSI or APSI. 相似文献
7.
Judit M. Pap Richard C. Willson Claus Fröhlich Richard F. Donnelly Larry Puga 《Solar physics》1994,152(1):13-21
For more than a decade total solar irradiance has been monitored simultaneously from space by different satellites. The detection of total solar irradiance variations by satellite-based experiments during the past decade and a half has stimulated modeling efforts to help identify their causes and to provide estimates of irradiance data, using proxy indicators of solar activity, for time intervals when no satellite observations exist. In this paper total solar irradiance observed by the Nimbus-7/ERB, SMM/ACRIM I, and UARS/ACRIM II radiometers is modeled with the Photometric Sunspot Index and the Mg II core-to-wing ratio. Since the formation of the Mg II line is very similar to that of the Ca II K line, the Mg core-to-wing ratio, derived from the irradiance observations of the Nimbus-7 and NOAA9 satellites, is used as a proxy for the bright magnetic elements. It is shown that the observed changes in total solar irradiance are underestimated by the proxy models at the time of maximum and during the beginning of the declining portion of solar cycle 22 similar to behavior just before the maximum of solar cycle 21. This disagreement between total irradiance observations and their model estimates is indicative of the fact that the underlying physical mechanism of the changes observed in the solar radiative output is not well-understood. Furthermore, the uncertainties in the proxy data used for irradiance modeling and the resulting limitation of the models should be taken into account, especially when the irradiance models are used for climatic studies. 相似文献
8.
The study of variations in total solar irradiance (TSI) and spectral irradiance is important for understanding how the Sun affects the Earth’s climate. A data-driven approach is used in this article to analyze and model the temporal variation of the TSI and Mg?ii index back to 1947. In both cases, observed data in the time interval of the satellite era, 1978?–?2013, were used for neural network (NN) model-design and testing. For this particular purpose, the evolution of the solar magnetic field is assumed to be the main driver for the day-to-day irradiance variability. First, we design a model for the Mg?ii index data from F10.7 cm solar radio-flux using the NN approach in the time span of 1978 through 2013. Results of Mg?ii index model were tested using various numbers of hidden nodes. The predicted values of the hidden layer with five nodes correspond well to the composite Mg?ii values. The model reproduces 94% of the variability in the composite Mg?ii index, including the secular decline between the 1996 and 2008 solar cycle minima. Finally, the extrapolation of the Mg?ii index was performed using the developed model from F10.7 cm back to 1947. Similarly, the NN model was designed for TSI variability study over the time span of the satellite era using data from the Physikalisch-Meteorologisches Observatorium Davos (PMOD) as a target, and solar activity indices as model inputs. This model was able to reproduce the daily irradiance variations with a correlation coefficient of 0.937 from sunspot and facular measurements in the time span of 1978?–?2013. Finally, the temporal variation of the TSI was analyzed using the designed NN model back to 1947 from the Photometric Sunspot Index (PSI) and the extrapolated Mg?ii index. The extrapolated TSI result indicates that the amplitudes of Solar Cycles 19 and 21 are closely comparable to each other, and Solar Cycle 20 appears to be of lower irradiance during its maximum. 相似文献
9.
Judit Pap 《Solar physics》1987,112(1):181-193
Measurements of the Nimbus-7/ERB and SMM/ACRIM radiometers indicated several dips in the total solar irradiance in 1983 and in the first part of 1984. The dips in 1983, which should have a real solar origin, were selected according to the peaks of the projected areas of the active sunspot groups above the 2 error limit of their data set. In the first part of 1984 the sunspot activity was strong and few irradiance dips with relatively large amplitudes were observed. In the second part of 1984 the sunspot activity disappeared and at that time the solar constant only fluctuated around its mean. 相似文献
10.
Analyses based on irradiance observations from space within the last one and a half decades have discovered variations in the entire solar spectrum and at UV wavelengths on time scales of minutes to decades. In this paper we analyze the distribution of the measuring uncertainties and daily fluctuations in total solar irradiance measured by the Nimbus-7/ERB and SMM/ACRIM I radiometers as a function of solar cycle. Changes in solar total irradiance and its surrogates shorter than the solar rotation have also been considered as noise and have been removed from the data. Our results show that the noise (both instrumental and solar noise) changes as a function of the solar cycle, being higher during high solar activity conditions. The analysis of the scatter plot diagrams between the data and their standard deviation, the so-called dispersion diagrams, provides a useful tool to estimate and predict the time of solar maximum and minimum activity conditions.Deceased on October 13, 1994. 相似文献
11.
Jun Nishikawa 《Solar physics》1994,152(1):125-130
Spatially-resolved precise photometric observations of the whole Sun at wavelengths of 545nm (FWHM 40nm) were carried out by using the CCD solar surface photometer. Bright parts of photospheric network have contrast of several tenths of percent, and their contribution to the total irradiance is approximately half that of active region faculae. The solar irradiance variations estimated from sunspots, faculae and active network (contrast>0.3%) agreed with the ACRIM data. The quiet Sun irradiance used in the present results was different from the total irradiance at the solar minimum observed by the ACRIM, which indicates unmeasured components (contrast>0.1%) cause the 11-year cycle irradiance variation. 相似文献
12.
A numerical technique of time-longitude analysis has been developed by studying the fine structure of temporal variations in total solar irradiance (TSI). This analysis produces maps of large-scale thermal inhomogeneities on the Sun and reveals corresponding patterns of radiative excess and deficit relative to the unperturbed solar photosphere. These patterns are organized in two-and four-sector structures and exhibit the effects of both activity complexes and the active longitudes. Large-scale patterns with radiative excess show a facular macrostructure caused by the relaxation of large-scale thermo-magnetic perturbations and/or energy output due to very large-scale solar convection. These thermal patterns are related to long-lived magnetic fields that are characterized by rigid rotation. The patterns with radiative excess tend to concentrate around the active longitudes and are centered at 103° and 277° in the Carrington system when averaged over the time-longitude distribution of thermal inhomogeneities during activity cycles 21–23. 相似文献
13.
George L. Withbroe 《Solar physics》2009,257(1):71-81
The daily images and magnetograms acquired by MDI are a rich source of information about the contributions of different types
of solar regions to variations in the total solar irradiance (TSI). These data have been used to determine the temporal variation
of the MDI irradiance, the mean intensity of the solar disk in the continuum at 676.8 nm. The short-term (days to weeks) variations
of the MDI irradiance and TSI are in excellent agreement with rms differences of 0.011%. This indicates that MDI irradiance
is an excellent proxy for short-term variations of TSI from the competing irradiance contributions of regions causing irradiance
increases, such as plages and bright network, and regions causing irradiance decreases, such as sunspots. However, the long-term
or solar cycle variation of the MDI proxy and TSI differ over the 11-year period studied. The results indicate that the primary
sources of the long-term (several months or more) variations in TSI are regions with magnetic fields between about 80 and
600 G. The results also suggest that the difference in the long-term variations of the MDI proxy and TSI is due to a component
of TSI associated with sectors of the solar spectrum where the contrast in intensity between plages and the quiet Sun is enhanced
(e.g., the UV) compared to the MDI proxy. This is evidence that the long-term variation of TSI is due primarily to solar cycle
variations of the irradiance from these portions of solar spectrum, a finding consistent with modeling calculations indicating
that approximately 60% of the change in TSI between solar minimum and maximum is produced by the UV part of the spectrum shortward
of 400 nm (Solanki and Krivova, Space Sci. Rev. 125, 53, 2006). 相似文献
14.
Our study deals with the correlations between the solar activity on the one hand and the solar irradiance above the Earth’s
atmosphere and at ground level on the other. We analyzed the combined ACRIM I+II time series of the total solar irradiance
(TSI), the Mauna Loa time series of terrestrial insolation data, and data of terrestrial cosmic ray fluxes. We find that the
correlation between the TSI and the sunspot number is strongly non-linear. We interpret this as the net balance between brightening
by faculae and darkening by sunspots where faculae dominate at low activity and sunspots dominate at high activity. Such a
behavior is hitherto known from stellar analogs of the Sun in a statistical manner. We perform the same analysis for the Mauna
Loa data of terrestrial insolation. Here we find that the linear relation between sunspot number and insolation shows more
than 1% rise in insolation by sunspot number variations which is much stronger than for the TSI. Our conclusion is that the
Earth atmosphere acts as an amplifier between space and ground, and that the amplification is probably controlled by solar
activity. We suspect the cosmic rays intensity as the link between solar activity and atmospheric transparency. A Fourier
analysis of the time series of insolation shows three dominant peaks: 10.5, 20.4, and 14.0 years. As a matter of fact, the
cosmic rays data show the same pattern of significant peaks: 10.7, 22.4, and 14.9 years. This analogy supports our idea that
the cosmic rays variation has influence on the transparency of the Earth atmosphere. 相似文献
15.
A. T. Mecherikunnel 《Solar physics》1994,155(2):211-221
This paper presents a statistical comparison of the solar total irradiance measured from the Nimbus-7, the Solar Maximum Mission (SMM), the Earth Radiation Budget Satellite (ERBS), and the Upper Atmosphere Research Satellite (UARS) spacecraft platforms, for the period 1985 –1992. The mean irradiance, standard deviation, and the correlation among the daily irradiance remained high during periods of high solar activity. Linear regression models are established to estimate the irradiance measurements from one platform by the others. The results are consistent with the observations. However, the Nimbus-7 ERB responses show a drift during 1989–1992. The absolute irradiance observed by each instrument varies within the uncertainty associated with the corresponding radiometer. 相似文献
16.
太阳总辐照是指在地球大气层顶接收到的太阳总辐射照度,也叫"太阳常数",但它实际上并非常数。太阳总辐照随波长的分布即为太阳分光辐照。太阳辐照变化的研究,对理解太阳表面及内部活动的物理过程、机制,研究地球大气、日地关系,解决人类面临的全球气候变暖的挑战等,都具有重要意义。首先简单介绍了太阳辐照,回顾了太阳辐照的空间观测;接着介绍了观测数据的并合,以及对合成数据的一些研究;然后讨论了太阳辐照变化的原因,简述了太阳总辐照的重构及其在气候研究上的一些应用,并进行必要的评论;最后对未来的研究方向提出了一些看法。 相似文献
17.
The solar spectral irradiance (SSI) dataset is a key record for studying and understanding the energetics and radiation balance in Earth’s environment. Understanding the long-term variations of the SSI over timescales of the 11-year solar activity cycle and longer is critical for many Sun–Earth research topics. Satellite measurements of the SSI have been made since the 1970s, most of them in the ultraviolet, but recently also in the visible and near-infrared. A limiting factor for the accuracy of previous solar variability results is the uncertainties for the instrument degradation corrections, which need fairly large corrections relative to the amount of solar cycle variability at some wavelengths. The primary objective of this investigation has been to separate out solar cycle variability and any residual uncorrected instrumental trends in the SSI measurements from the Solar Radiation and Climate Experiment (SORCE) mission and the Thermosphere, Mesosphere, Ionosphere, Energetic, and Dynamics (TIMED) mission. A new technique called the Multiple Same-Irradiance-Level (MuSIL) analysis has been developed, which examines an SSI time series at different levels of solar activity to provide long-term trends in an SSI record, and the most common result is a downward trend that most likely stems from uncorrected instrument degradation. This technique has been applied to each wavelength in the SSI records from SORCE (2003?–?present) and TIMED (2002?–?present) to provide new solar cycle variability results between 27 nm and 1600 nm with a resolution of about 1 nm at most wavelengths. This technique, which was validated with the highly accurate total solar irradiance (TSI) record, has an estimated relative uncertainty of about 5% of the measured solar cycle variability. The MuSIL results are further validated with the comparison of the new solar cycle variability results from different solar cycles. 相似文献
18.
Peter Foukal 《Solar physics》2012,279(2):365-381
We compare total solar irradiance (TSI) and ultraviolet (F uv) irradiance variation reconstructed using Ca?K facular areas since 1915, with previous values based on less direct proxies. Our annual means for 1925??C?1945 reach values 30??C?50?% higher than those presently used in IPCC climate studies. A high facula/sunspot area ratio in spot cycles 16 and 17 seems to be responsible. New evidence from solar photometry increases the likelihood of greater seventeenth century solar dimming than expected from the disappearance of magnetic active regions alone. But the large additional brightening in the early twentieth century claimed from some recent models requires complete disappearance of the magnetic network. The network is clearly visible in Ca K spectroheliograms obtained since the 1890s, so these models cannot be correct. Changes in photospheric effective temperature invoked in other models would be powerfully damped by the thermal inertia of the convection zone. Thus, there is presently no support for twentieth century irradiance variation besides that arising from active regions. The mid-twentieth century irradiance peak arising from these active regions extends 20 years beyond the early 1940s peak in global temperature. This failure of correlation, together with the low amplitude of TSI variation and the relatively weak effect of Fuv driving on tropospheric temperature, limits the role of solar irradiance variation in twentieth century global warming. 相似文献
19.
Hirokazu Yoshimura 《Astronomische Nachrichten》1995,316(3):175-186
We found an evidence that the solar cycle luminosity modulation of the Sun deduced from the total irradiance modulation which was measured by the Earth Radiation Budget (ERB) experiment on board of Nimbus 7 from November 16, 1978 to December 13, 1993 was not in phase with the solar cycle magnetic oscillation when we used the sunspot relative number as its index. The modulation was delayed in time behind the solar cycle magnetic oscillation by an amount of about 10.3 years on the order of length of one solar cycle. In order to quantitatively evaluate the correlation between the two quantities, we devised a method to extract characteristics which were proper to a particular solar cycle by defining a new index of the correlation called multiplied correlation index (MCI). We found that the characteristics of the ERB data time profile between solar cycles 21 and 22 were more similar to those of the solar cycle magnetic oscillation between solar cycles 20 and 21 than those between solar cycles 21 and 22 and thus the time profile of the luminosity modulation from the maximum phase of solar cycle 21 to the declining phase of the solar cycle 22 corresponded to the solar cycle magnetic oscillation from the maximum phase of solar cycle 20 to the declining phase of solar cycle 21. We interpret this phenomenon as an evidence that main features of the modulation is not caused by dark sunspots and bright faculae and plages on the surface of the Sun that should instantaneously affect the luminosity modulation but is caused by time-delayed modulation of global convection by the Lorentz force of the magnetic field of the solar cycle. The delay time of about 10.3 years is the time needed for the force to modify the flows of the convection and to modulate heat flow. Thus the delay time is a function of the strength of the magnetic field oscillation of the solar cycle which is represented by amplitude of the solar cycle. Accordingly, the delay time for other time intervals of the solar cycle magnetic oscillation with different amplitudes can be different from 10.3 years for the interval of the present analysis. 相似文献
20.
The growing interest in the Medieval Climate Anomaly (MCA) and its possible link to anomalous solar activity has prompted new reconstructions of solar activity based on cosmogenic radionuclides. However, these proxies do not sufficiently constrain the total solar irradiance (TSI) range and are often defined at low temporal resolution, inadequate to infer the solar-cycle length (SCL). We have reconstructed the SCL (average duration of 10.72±0.20 years) during the MCA using observations of naked-eye sunspot and aurora sightings. The solar activity was probably not exceptionally intense, supporting the view that internal variability of the coupled ocean–atmosphere system was the main driver of the MCA. 相似文献