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1.
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   

2.
Knowledge of solar spectral irradiance (SSI) is important in determining the impact of solar variability on climate. Observations of UV SSI have been made by the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) on the Upper Atmosphere Research Satellite (UARS), the Solar-Stellar Irradiance Comparison Experiment (SOLSTICE), and the Solar Irradiance Monitor (SIM), both on the Solar Radiation and Climate Experiment (SORCE) satellite. Measurements by SUSIM and SORCE overlapped from 2003 to 2005. SUSIM and SORCE observations represent ～?20 years of absolute UV SSI. Unfortunately, significant differences exist between these two data sets. In particular, changes in SORCE UV SSI measurements, gathered at moderate and minimum solar activity, are a factor of two greater than the changes in SUSIM observations over the entire solar cycle. In addition, SORCE UV SSI have a substantially different relationship with the Mg ii index than did earlier UV SSI observations. Acceptance of these new SORCE results impose significant changes on our understanding of UV SSI variation. Alternatively, these differences in UV SSI observations indicate that some or all of these instruments have changes in instrument responsivity that are not fully accounted for by the current calibration. In this study, we compare UV SSI changes from SUSIM with those from SIM and SOLSTICE. The primary results are that (1) long-term observations by SUSIM and SORCE generally do not agree during the overlap period (2003?–?2005), (2) SUSIM observations during this overlap period are consistent with an SSI model based on Mg ii and early SUSIM SSI, and (3) when comparing the spectral irradiance for times of similar solar activity on either side of solar minimum, SUSIM observations show slight differences while the SORCE observations show variations that increase with time between spectra. Based on this work, we conclude that the instrument responsivity for SOLSTICE and SIM need to be reevaluated before these results can be used for climate-modeling studies.  相似文献   

3.
The Total Irradiance Monitor (TIM): Science Results   总被引：2，自引：0，他引：2  
The solar observations from the Total Irradiance Monitor (TIM) are discussed since the SOlar Radiation and Climate Experiment (SORCE) launch in January 2003. The TIM measurements clearly show the background disk-integrated solar oscillations of generally less than 50 parts per million (ppm) amplitude over the ∼2 ppm instrument noise level. The total solar irradiance (TSI) from the TIM is about 1361 W/m2, or 4–5 W/m2 lower than that measured by other current TSI instruments. This difference is not considered an instrument or calibration error. Comparisons with other instruments show excellent agreement of solar variability on a relative scale. The TIM observed the Sun during the extreme activity period extending from late October to early November 2003. During this period, the instrument recorded both the largest short-term decrease in the 25-year TSI record and also the first definitive detection of a solar flare in TSI, from which an integrated energy of roughly (6± 3)×1032 ergs from the 28 October 2003 X17 flare is estimated. The TIM has also recorded two planets transiting the Sun, although only the Venus transit on 8 June 2004 was definitive.  相似文献   

4.
Aparicio  A. J. P.  Lefèvre  L.  Gallego  M. C.  Vaquero  J. M.  Clette  F.  Bravo-Paredes  N.  Galaviz  P.  Bautista  M. L. 《Solar physics》2018,293(12):1-23

The Spectral Irradiance Monitor (SIM) instrument on board the Solar Radiation and Climate Experiment (SORCE) performs daily measurements of the solar spectral irradiance (SSI) from 200 to 2400 nm. Both temporal and spectral corrections for instrument degradation have been built on physical models based on comparison of two independent channels with different solar exposure. The present study derives a novel correction for SIM degradation using the total solar irradiance (TSI) measurements from the Total Irradiance Monitor (TIM) on SORCE. The correction is applied to SIM SSI data from September 2004 to October 2012 over the wavelength range from 205 nm to 2300 nm. The change in corrected, integrated SSI agrees within \(0.1~\mbox{W}\,\mbox{m}^{-2}\) (\(1\sigma\)) with SORCE TIM TSI and independently shows agreement with the SATIRE-S and NRLSSI2 solar models within measurement uncertainties.

  相似文献   

5.
The Picard spacecraft was successfully launched on 15 June 2010, into a Sun-synchronous orbit. The mission represents one of the European contributions to solar observations and Essential Climate Variables (ECVs) measurements. The payload is composed of a Solar Diameter Imager and Surface Mapper (SODISM) and two radiometers: SOlar VAriability Picard (SOVAP) and PREcision MOnitor Sensor (PREMOS). SOVAP, a dual side-by-side cavity radiometer, measures the total solar irradiance (TSI). It is the sixth of a series of differential absolute-radiometer-type instruments developed and operated in space by the Royal Meteorological Institute of Belgium. The measurements of SOVAP in the summer of 2010 yielded a TSI value of 1362.1 W?m?2 with an uncertainty of ±?2.4 W?m?2 (k=1). During the periods of November 2010 and January 2013, the amplitude of the changes in TSI has been on the order of 0.18 %, corresponding to a range of about 2.4 W?m?2.  相似文献   

6.
The NASA Earth Observing System (EOS) is an advanced study of Earth's long-term global changes of solid Earth, its atmosphere, and oceans and includes a coordinated collection of satellites, data systems, and modeling. The EOS program was conceived in the 1980s as part of NASA's Earth System Enterprise (ESE). The Solar Radiation and Climate Experiment (SORCE) is one of about 20 missions planned for the EOS program, and the SORCE measurement objectives include the total solar irradiance (TSI) and solar spectral irradiance (SSI) that are two of the 24 key measurement parameters defined for the EOS program. The SORCE satellite was launched in January 2003, and its observations are improving the understanding and generating new inquiry regarding how and why solar variability occurs and how it affects Earth's energy balance, atmosphere, and long-term climate changes.  相似文献   

7.
We present a model for the reconstruction of spectral solar irradiance between 200 and 400?nm. This model is an extension of the total solar irradiance (TSI) model of Crouch et al. (Astrophys.?J. 677, 723, 2008) which is based on a data-driven Monte Carlo simulation of sunspot emergence, fragmentation, and erosion. The resulting time-evolving daily area distribution of magnetic structures of all sizes is used as input to a four-component irradiance model including contributions from the quiet Sun, sunspots, faculae, and network. In extending the model to spectral irradiance in the near- and mid-ultraviolet, the quiet Sun and sunspot emissivities are calculated from synthetic spectra at T eff=5750?K and 5250?K, respectively. Facular emissivities are calculated using a simple synthesis procedure proposed by Solanki and Unruh (Astron. Astrophys. 329, 747, 1998). The resulting time series of ultraviolet flux is calibrated against the data from the SOLSTICE instrument on the Upper Atmospheric Research Satellite (UARS). Using a genetic algorithm, we invert quiet Sun corrections, profile of facular temperature variations with height, and network model parameters which yield the best fit to these data. The resulting best-fit time series reproduces quite well the solar-cycle timescale variations of UARS ultraviolet observations, as well as the short-timescale fluctuations about the 81 day running mean. We synthesize full spectra between 200 and 400?nm, and validate these against the spectra obtained by the ATLAS-1 and ATLAS-3 missions, finding good agreement, to better than 3?% at most wavelengths. We also compare the UV variability predicted by our reconstructions in the descending phase of sunspot cycle 23 to SORCE/SIM data as well as to other reconstructions. Finally, we use the model to reconstruct the time series of spectral irradiance starting in 1874, and investigate temporal correlations between pairs of wavelengths in the bands of interest for stratospheric chemistry and dynamics.  相似文献   

8.
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   

9.
The SORCE Science Data System produces total solar irradiance (TSI) and spectral solar irradiance (SSI) data products on a daily basis, which are formulated using measurements from the four primary instruments onboard the SORCE spacecraft. The Science Data System utilizes raw spacecraft and instrument telemetry, calibration data, and other ancillary information to produce and distribute a variety of data products that have been corrected for all known instrumental and operational effects. SORCE benefits from a highly optimized object-oriented data processing system in which all data are stored in a commercial relational database system, and the software itself determines the versions of data products at run-time. This unique capability facilitates optimized data storage and CPU utilization during reprocessing activities by requiring only new data versions to be generated and stored. This paper provides an overview of the SORCE data processing system, details its design, implementation, and operation, and provides details on how to access SORCE science data products.  相似文献   

10.
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   

11.
We analyze the variability of the spectral solar irradiance during the period from 7 January 2010 until 20 January 2010 as measured by the Herzberg channel (190?–?222 nm) of the Large Yield RAdiometer (LYRA) onboard PROBA2. In this period of time, observations by the LYRA nominal unit experienced degradation and the signal produced by the Herzberg channel frequently jumped from one level to another. Both factors significantly complicate the analysis. We present the algorithm that allowed us to extract the solar variability from the LYRA data and compare the results with SORCE/SOLSTICE measurements and with modeling based on the Code for the Solar Irradiance (COSI).  相似文献   

12.
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   

13.
Relations between basic indices of the Sun and the cosmogenic isotope 14C and 10Be records were derived using the Artificial Neural Network (ANN) technique. A reconstruction of the sunspot indices and changes in Total Solar Irradiance (TSI) was carried out. Long-term changes in TSI appear in the amplitude modulation of its 11-year cyclic variation as well as in its lower envelope describing variability of the background irradiance of the Sun. According to the reconstruction the irradiance has increased about 2.5 W m−2 since 1441.  相似文献   

14.
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   

15.
The total solar irradiance (TSI) has been recorded daily since October 2013 by the Total Solar Irradiance Monitor (TSIM) onboard the FY-3C satellite, which is mainly designed for Earth observation. The TSIM has a pointing system to perform solar tracking using a sun sensor. The TSI is measured by two electrical substitution radiometers with traceability to the World Radiation Reference. The TSI value measured with the TSIM on 2 October 2013 is \(1364.88~\mbox{W}\,\mbox{m}^{-2}\) with an uncertainty of \(1.08~\mbox{W}\,\mbox{m}^{-2}\). Short-term TSI variations recorded with the TSIM show good agreement with SOHO/VIRGO and SORCE/TIM. The data quality and accuracy of FY-3C/TSIM are much better than its predecessors on the FY-3A and FY-3B satellites, which operated in a scanning mode.  相似文献   

16.
Results of astrometric and BVRI photometric observations of the active asteroid (596) Scheila are presented. The observations were carried out at the Zeiss-1000 telescope of the Sanglokh International Astronomical Observatory of the Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan on June 16?17 and from July 30 to August 1, 2017. The coordinates of the object and its orbit were determined; and the apparent brightness in four filters, the absolute brightness in the V and R filters, and the color indices were obtained. The light curves suggest that no substantial changes in the asteroid’s brightness occurred during the observations. The absolute brightness of the asteroid in the V and R filters was (9.1 ± 0.05)m and (8.8 ± 0.03)m, respectively. The mean value of the asteroid diameter was (119 ± 2) km. The mean values of the color indices (B?V = (0.72 ± 0.05)m, V?R = (0.29 ± 0.03)m, and R?I = (0.31 ± 0.03)m) agree well with the values for asteroids of the P- and D-types and its averages. The rotation period of the asteroid estimated from photometric observations was 16.1 ± 0.2 h. The analysis of the data has shown that the asteroid continues to exhibit the same values of absolute brightness and other characteristics as those before the collision with a small body in December 2010, though the latter resulted in the outburst event and cometary activity of the asteroid. Most likely, the collision of asteroid (596) Scheila with a small body did not lead to catastrophic changes in the surface of the asteroid or to its compete break-up.  相似文献   

17.
We have compared total solar irradiance from Nimbus-7 with ground-based photometry from the San Fernando Observatory (SFO) for 109 days between June 1 and December 31, 1988. We have also included in some analyses NOAA-9 SBUV2 data orF10.7 radio flux. The Nimbus-7 data are from orbital samples, averaged to the mean time of observation at SFO. Using the same parameters as in Chapmanet al. (1992), the multiple regression gives anR 2 = 0.9131 and a solar minimum irradiance,S 0, = 1371.76 ± 0.18 W m–2 for the best fit.  相似文献   

18.
There has been much speculation about the extended minimum between Solar Cycles 23 and 24. Cycle 24 itself has been unusually weak compared with recent cycles. We present quantitative evidence for the weakness of both Cycles 23 and, particularly, 24. The data are objective indices derived from precision photometric images obtained on a daily basis at the San Fernando Observatory. These data form the longest running, homogeneous photometric record known to us. We show sunspot areas from red images and facular/network areas from Ca ii K-line images. Spot and facular area are a simple and direct measurement of the strength of solar activity. The data clearly show the decline in the amplitude of sunspot maxima for Cycles 23 and 24 compared with Cycle 22. The relative amplitudes of mean spot area for Cycles 22 through 24 are 1.0, 0.74, and 0.37, respectively. There is also an indication that the facular-to-spot area ratio has increased in Cycle 24.  相似文献   

19.
The satellite total solar irradiance (TSI) database provides a valuable record for investigating models of solar variation used to interpret climate changes. The 35-year ACRIM total solar irradiance (TSI) satellite composite time series has been revised using algorithm updates based on 13 years of accumulated mission experience and corrections to ACRIMSAT/ACRIM3 results for scattering and diffraction derived from recent testing at the Laboratory for Atmospheric and Space Physics/Total solar irradiance Radiometer Facility (LASP/TRF). The net correction lowers the ACRIM3 scale by ～3000 ppm, in closer agreement with the scale of SORCE/TIM results (average total solar irradiance ≈1361.5 W/m2). Differences between the ACRIM and PMOD TSI composites are investigated, particularly the decadal trending during solar cycles 21–22 and the Nimbus7/ERB and ERBS/ERBE results available to bridge the ACRIM Gap (1989–1992), are tested against a set of solar proxy models. Our findings confirm the following ACRIM TSI composite features: (1) The validity of the TSI peak in the originally published ERB results in early 1979 during solar cycle 21; (2) The correctness of originally published ACRIM1 results during the SMM spin mode (1981–1984); (3) The upward trend of originally published ERB results during the ACRIM Gap; (4) The occurrence of a significant upward TSI trend between the minima of solar cycles 21 and 22 and (5) a decreasing trend during solar cycles 22–23. The same analytical approach does not support some important features of the PMOD TSI composite: (1) The downward corrections applied to the originally published ERB and ACRIM1 results during solar cycle 21; (2) The step function sensitivity change in ERB results at the end-of-September 1989; (3) The downward trend of ERBE results during the ACRIM Gap and (4) the use of ERBE results to bridge the ACRIM Gap. Our analysis provides a first order validation of the ACRIM TSI composite approach and its 0.037 %/decade upward trend during solar cycles 21–22. The implications of increasing TSI during the global warming of the last two decades of the 20th century are that solar forcing of climate change may be a significantly larger factor than represented in the CMIP5 general circulation climate models.  相似文献   

20.
Analyzing daily values of the total solar irradiance (TSI), the coronal index of solar activity (CI), and the Mg II 280-nm core-to-wing ratio (Mg II index), we have found that the temporal variations of these indices are very similar to each other during the period from 1978 to 2005. The correlation between CI and TSI, with the PSI correction lying within the interval under study, has been found to be 0.699, which is very close to the value of 0.703 of the correlation between Mg II and TSI for 27-day averages (the CI – Mg correlation is 0.824). The regression equation between CI and TSI is almost linear, except for TSI depletions when a large number of sunspots are present on the visible disk. By employing CI, an extrapolation of TSI back to 1947 is presented.  相似文献   

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