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1.
J. M. Borrero S. Tomczyk M. Kubo H. Socas-Navarro J. Schou S. Couvidat R. Bogart 《Solar physics》2011,273(1):267-293
In this paper we describe in detail the implementation and main properties of a new inversion code for the polarized radiative
transfer equation (VFISV: Very Fast Inversion of the Stokes Vector). VFISV will routinely analyze pipeline data from the Helioseismic
and Magnetic Imager (HMI) on-board of the Solar Dynamics Observatory (SDO). It will provide full-disk maps (4096×4096 pixels)
of the magnetic field vector on the Solar Photosphere every ten minutes. For this reason VFISV is optimized to achieve an
inversion speed that will allow it to invert sixteen million pixels every ten minutes with a modest number (approx. 50) of
CPUs. Here we focus on describing a number of important details, simplifications and tweaks that have allowed us to significantly
speed up the inversion process. We also give details on tests performed with data from the spectropolarimeter on-board of
the Hinode spacecraft. 相似文献
2.
Roger K. Ulrich Larry Webster John E. Boyden Nick Magnone Richard S. Bogart 《Solar physics》1991,135(2):211-241
We describe enhancements to the hardware and software for the 150-foot tower system on Mt. Wilson which make possible the acquisition of high precision line profile measurements. This system utilizes the 75-foot pit spectrograph with a photomultiplier detector system to scan line profiles repeatedly in order to study variations induced by the passage of waves vertically through the solar atmosphere. Oscillations of line profile parameters with an amplitude as low as 1.7 m s–1 have been detected with this system using integrated sunlight. Phase relations between oscillations of different parts of the line profile are appropriate to upward energy transport. Consistent with the previous conclusion by Mein and Schmieder (1981), we find that the magnitude of the energy transport is compatible with the 5-min oscillations making an important contribution to the heating of the low chromosphere.The Mount Wilson Observatory is operated by the Mount Wilson Institute under agreement with the Carnegie Institution of Washington. 相似文献
3.
4.
J. Schou P. H. Scherrer R. I. Bush R. Wachter S. Couvidat M. C. Rabello-Soares R. S. Bogart J. T. Hoeksema Y. Liu T. L. Duvall Jr. D. J. Akin B. A. Allard J. W. Miles R. Rairden R. A. Shine T. D. Tarbell A. M. Title C. J. Wolfson D. F. Elmore A. A. Norton S. Tomczyk 《Solar physics》2012,275(1-2):229-259
5.
Hathaway D.H. Beck J.G. Bogart R.S. Bachmann K.T. Khatri G. Petitto J.M. Han S. Raymond J. 《Solar physics》2000,193(1-2):299-312
Spectra of the cellular photospheric flows are determined from observations acquired by the MDI instrument on the SOHO spacecraft. Spherical harmonic spectra are obtained from the full-disk observations. Fourier spectra are obtained from the high-resolution observations. The p-mode oscillation signal and instrumental artifacts are reduced by temporal filtering of the Doppler data. The resulting spectra give power (kinetic energy) per wave number for effective spherical harmonic degrees from 1 to over 3000. Significant power is found at all wavenumbers, including the small wavenumbers representative of giant cells. The time evolution of the spectral coefficients indicates that these small wavenumber components rotate at the solar rotation rate and thus represent a component of the photospheric cellular flows. The spectra show distinct peaks representing granules and supergranules but no distinct features at wavenumbers representative of mesogranules or giant cells. The observed cellular patterns and spectra are well represented by a model that includes two distinct modes – granules and supergranules. 相似文献
6.
R. S. Bogart S. H. Ferguson P. H. Scherrer T. D. Tarbell A. M. Title 《Solar physics》1988,116(2):205-214
The SOUP experiment demonstrated that photospheric surface flows can be measured by correlation tracking of white-light intensity features at high resolution (November et al., 1987). In order to assess the feasibility of this technique with observations made at lower resolution, we have applied it to the same SOUP data artificially degraded, but still free of seeing distortion. Comparison with the velocity structures inferred from the original data shows generally good agreement when the resolution is better than about 2. The radial outflow from a sunspot penumbra, however, can only be seen with resolution of better than 1. With resolution of worse than 2, the inferred velocity fields rapidly lose coherence, while resolution of better than 1 yields little improvement. We conclude that apertures as small as 10–14 cm on a space-based platform will be useful for the measurement of large-scale horizontal motions. 相似文献
7.
P. H. Scherrer R. S. Bogart R. I. Bush J. T. Hoeksema A. G. Kosovichev J. Schou W. Rosenberg L. Springer T. D. Tarbell A. Title C. J. Wolfson I. Zayer The MDI Engineering Team 《Solar physics》1995,162(1-2):129-188
The Solar Oscillations Investigation (SOI) uses the Michelson Doppler Imager (MDI) instrument to probe the interior of the Sun by measuring the photospheric manifestations of solar oscillations. Characteristics of the modes reveal the static and dynamic properties of the convection zone and core. Knowledge of these properties will improve our understanding of the solar cycle and of stellar evolution. Other photospheric observations will contribute to our knowledge of the solar magnetic field and surface motions. The investigation consists of coordinated efforts by several teams pursuing specific scientific objectives.The instrument images the Sun on a 10242 CCD camera through a series of increasingly narrow spectral filters. The final elements, a pair of tunable Michelson interferometers, enable MDI to record filtergrams with a FWHM bandwidth of 94 m. Normally 20 images centered at 5 wavelengths near the Ni I 6768 spectral line are recorded each minute. MDI calculates velocity and continuum intensity from the filtergrams with a resolution of 4 over the whole disk. An extensive calibration program has verified the end-to-end performance of the instrument.To provide continuous observations of the longest-lived modes that reveal the internal structure of the Sun, a carefully-selected set of spatial averages are computed and downlinked at all times. About half the time MDI will also be able to downlink complete velocity and intensity images each minute. This high rate telemetry (HRT) coverage is available for at least a continuous 60-day interval each year and for 8 hours each day during the rest of the year. During the 8-hour HRT intervals, 10 of the exposures each minute can be programmed for other observations, such as measurements in MDI's higher resolution (1.25) field centered about 160 north of the equator; meanwhile, the continuous structure program proceeds during the other half minute. Several times each day, polarizers will be inserted to measure the line-of-sight magnetic field.MDI operations will be scheduled well in advance and will vary only during the daily 8-hour campaigns. Quick-look and summary data, including magnetograms, will be processed immediately. Most high-rate data will be delivered only by mail to the SOI Science Support Center (SSSC) at Stanford, where a processing pipeline will produce 3 Terabytes of calibrated data products each year. These data products will be analyzed using the SSSC and the distributed resources of the co-investigators. The data will be available for collaborative investigations.The MDI Engineering Team leaders include: D. Akin, B. Carvalho, R. Chevalier, D. Duncan, C. Edwards, N. Katz, M. Levay, R. Lindgren, D. Mathur, S. Morrison, T. Pope, R. Rehse, and D. Torgerson. 相似文献
8.
Kosovichev A. G. Schou J. Scherrer P. H. Bogart R. S. Bush R. I. Hoeksema J. T. Aloise J. Bacon L. Burnette A. De Forest C. Giles P. M. Leibrand K. Nigam R. Rubin M. Scott K. Williams S. D. Basu Sarbani Christensen-dalsgaard J. DÄppen W. Duvall T. L. Howe R. Thompson M. J. Gough D. O. Sekii T. Toomre J. Tarbell T. D. Title A. M. Mathur D. Morrison M. Saba J. L. R. Wolfson C. J. Zayer I. Milford P. N. 《Solar physics》1997,170(1):43-61
The medium-l program of the Michelson Doppler Imager instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to 300. The data for the program are partly processed on board because only about 3% of MDI observations can be transmitted continuously to the ground. The on-board data processing, the main component of which is Gaussian-weighted binning, has been optimized to reduce the negative influence of spatial aliasing of the high-degree oscillation modes. The data processing is completed in a data analysis pipeline at the SOI Stanford Support Center to determine the mean multiplet frequencies and splitting coefficients. The initial results show that the noise in the medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. This is important for inferring the Sun's internal structure and rotation. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. The results also confirm the previous finding by the GONG (Gough et al., 1996) that, in a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer. This layer is likely to be the place where the solar dynamo operates. In order to understand how the Sun works, it is extremely important to observe the evolution of this transition layer throughout the 11-year activity cycle. 相似文献
9.
Frank Hill Piet Martens Keji Yoshimura Joseph Gurman Joseph Hourclé George Dimitoglou Igor Suárez-Solá Steve Wampler Kevin Reardon Alisdair Davey Richard S. Bogart Karen Q. Tian 《Earth, Moon, and Planets》2009,104(1-4):315-330
The Virtual Solar Observatory (VSO) has been developed to allow researchers, educators, and the general public to access data and images from the major sources of on-line solar data. The VSO substantially reduces the effort required to locate disparate data sets, and removes the need for the user to locate the data and learn multiple interfaces. The VSO provides a single interface to about 60 geographically distributed data sets including space- and ground-based sources. These data sets incorporate several physical variables including magnetic field, intensity, Doppler velocity, etc., and all wavelengths from X-ray to radio. All layers of the sun, from the interior to the corona, are included. In this paper we describe the system and present the interface that the user will encounter. We also discuss future enhancements planned for the system. 相似文献
10.
Recurrence of solar activity: Evidence for active longitudes 总被引：1，自引：0，他引：1
Richard S. Bogart 《Solar physics》1982,76(1):155-165
The autocorrelation coefficients of the daily Wolf sunspot numbers over a period of 128 years reveal a number of interesting features of the variability of solar activity. In addition to establishing periodicities for the solar rotation, the solar activity cycle, and perhaps the Gleissberg Cycle, they suggest that active longitudes do exist, but with much greater strength and persistence in some solar cycles than in others. There is evidence for a variation in the solar rotation period, as measured by sunspot number, of as much as two days between different solar cycles.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献