首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
GOLF (Global Oscillations at Low Frequencies) is an instrument to study the line-of-sight velocity of the solar photosphere, to be flown on the SOHO satellite in 1995. It uses a sodium vapour cell in resonance scattering mode, in order to measure the absolute Doppler shift of the solar sodium absorption lines. We have developed a model of the resonance cell performance. We describe here the main characteristics of the model, and report the most important results concerning the performance of the cell and its dependance on temperature.  相似文献   

2.
In the framework of the IRIS programme, full-disk solar Doppler-shift measurements are made with an optical resonance sodium cell spectrophotometer, a new pattern of the instrument successfully used at the geographic South Pole 10 years ago. After many successive improvements, the IRIS version has now become a precise and reliable device, being limited only by the solar and/or by the atmospheric noise in all the frequency ranges of interest for the p-mode and the g-mode investigation. This instrument is described here in some detail, with the technical specification for each individual component being defined by comparison to the photon and the solar noise.  相似文献   

3.
The GOLF experiment on the SOHO mission aims to study the internal structure of the sun by measuring the spectrum of global oscillations in the frequency range 10–7 to 10–2 Hz. Bothp andg mode oscillations will be investigated, with the emphasis on the low order long period waves which penetrate the solar core. The instrument employs an extension to space of the proven ground-based technique for measuring the mean line-of-sight velocity of the viewed solar surface. By avoiding the atmospheric disturbances experienced from the ground, and choosing a non-eclipsing orbit, GOLF aims to improve the instrumental sensitivity limit by an order of magnitude to 1 mm s–1 over 20 days for frequencies higher than 2.10–4 Hz. A sodium vapour resonance cell is used in a longitudinal magnetic field to sample the two wings of the solar absorption line. The addition of a small modulating field component enables the slope of the wings to be measured. This provides not only an internal calibration of the instrument sensitivity, but also offers a further possibility to recognise, and correct for, the solar background signal produced by the effects of solar magnetically active regions. The use of an additional rotating polariser enables measurement of the mean solar line-of-sight magnetic field, as a secondary objective.  相似文献   

4.
Cacciani  A.  Moretti  P. F. 《Solar physics》1997,175(1):1-13
Recently a new version of a sodium double-band magneto-optical filter has been built in order to provide simultaneous Doppler and magnetograms using the same optical path (Cacciani, Moretti, and Rodgers, 1997; Cacciani et al., 1988, 1994). Two observing stations based on this instrument are being installed as part of the French network IRIS. One is already operational in Apple Valley, California, and the other one will be delivered shortly to Tashkent, Uzbekistan. The performance of the instrument is such as to detect the l = 0 mode of solar oscillations from resolved images with a signal-to-noise ratio that has never been achieved before (Cacciani and Moretti, 1994). The magnetic and velocity signals are corrected for the changes that occur in the solar D-line profile in active versus non-active regions. This kind of analysis will be performed by our group in conjunction with parallel analysis of GOLF and IRIS integrated data which use the same sodium lines.  相似文献   

5.
A Magneto-Optical Filter-based system has been proposed as an optional payload for ASI’s low-budget Solar Mission ADAHELI, which has completed its Phase A feasibility study. The instrument is capable of providing simultaneous Dopplergrams, intensity and magnetic solar full-disk maps using the potassium 770 nm and sodium 589 nm solar Fraunhofer lines. The instrument is a version, re-designed for a space environment, of the one which has run an observing campaign at the South Pole in 2008 with unprecedented performance. The MOF-based system we present here is a low-cost, low-weight instrument, thus particularly fit to space applications, capable of providing stability and sensitivity of signals on long-term observations. The instrument will explore regions of the oscillation spectrum not available to other missions’ instruments.  相似文献   

6.
It is well known that the neutral component of the local interstellar medium can effectively pass through the plasma interface ahead of the solar system and can penetrate deeply into the inner heliosphere. Here we present a newly-developed theoretical approach to describe the distribution function of LISM neutral hydrogen in the heliosphere, also taking into account time-dependent solar and interstellar boundary conditions. For this purpose we start from a Boltzmann-Vlasov equation, Fourier-transformed with respect to space and time coordinates, in connection with correspondingly transformed solar radiation forces and ionization rates, and then arrive at semi-analytic solutions for the transformed hydrogen velocity distribution function. As interstellar boundary conditions we allow for very general, non-Maxwellian and time-dependent distribution functions to account for the case that some LISM turbulence patterns or nonlinear wave-like shock structures pass over the solar system. We consider this theoretical approach to be an ideal instrument for the synoptic interpretation of huge data samples on interplanetary Ly- resonance glow intensities registered from different celestial directions over extended periods of time. In addition we feel that the theoretical approach presented here, when applied to interplanetary resonance glow data, may permit the detection of genuine fluctuations in the local interstellar medium.  相似文献   

7.
Ｏｕｒｍｅｔｅｒｗａｖｅｓｏｌａｒｒａｄｉｏａｃｏｕｓｔｏ -ｏｐｔｉｃａｌｓｐｅｃｔｒｏｇｒａｐｈ(ＡＯＳ)ｔｒａｃｅｓｂａｃｋｔｏｔｈｅｙｅａｒ 1 979ｗｈｅｎｉｔｗａｓｂｅｉｎｇｂｕｉｌｔ.ＴｈｅＡＯＳｃｏｖｅｒｓａｗｏｒｋｉｎｇｆｒｅｑｕｅｎｃｙｒａｎｇｅｏｆ 2 30～ 30 0ＭＨｚ .Ｉｔｈａｓｔｈｅｍｅｒｉｔｓｏｆｈｉｇｈｓｐｅｃｔｒａｌｒｅｓｏｌｕｔｉｏｎａｎｄｇｏｏｄｓｅｎｓｉｔｉｖｉｔｙ .Ｔｈｅｓｐｅｃｔｒａｌｒｅｓｏｌｕｔｉｏｎ( 0 2 5ＭＨｚ)ｄｅ ｐｅｎｄｓｏｎｔｈｅｃｈａｒａｃｔｅｒｉｓ…  相似文献   

8.
In this paper a procedure to calibrate dopplergrams is presented. This procedure is instrument independent and is based on the main topological characteristics of solar rotation. It is reliable in those regions on the solar disk where the sensitivity can be considered linear in the east-west direction (that is, out to 0.75 solar radius for most instruments) and, in principle, can be applied to all dopplergrams with medium spatial resolution (typically 8 arc sec pixel–1). The aim of this calibration is to correct any variation of the sensitivity to the velocity signal caused by instrumental changes. The procedure is currently applied to data obtained at the Solar Observatory at Kanzelhöhe (Austria) with a sodium magneto-optical filter. The procedure, applied to a one-day run, shows how the low-degree five-min oscillations are recovered from the raw integrated Doppler signal over the whole CCD.  相似文献   

9.
Comets are probably the most primitive bodies of the solar system, and they participated in the early bombardment of the primitive planets. Consequently, the knowledge of their composition can play a key role in our understanding of the solar system formation, the origin of the planetary volatile constituents, and the origin of the organics implied in terrestrial prebiotic chemistry. However, we still do not have any direct information about the molecular composition of the cometary nucleus. This is why the COmetary SAmpling and Composition experiment (COSAC), onboard the surface landing probe of the Rosetta cometary mission, is specifically devoted to the molecular and enantiomeric analysis of a cometary nucleus. This experiment includes a gas chromatograph instrument dedicated to the specific identification and quantification of the general molecular species present in samples collected at the nucleus surface. In order to evaluate the performances of the integrated chromatographic system which was selected for the flight model instrument, experiments were carried out with a laboratory set up that reproduced the flight configuration and mimicked the in situ operating conditions. The obtained results demonstrate the ability for the gas chromatograph to identify a wide range of organic and inorganic volatile compounds, even those present at trace level, within the constrained space operating conditions. The aim of this paper is to present, for the first time, the performances of this system and to discuss the potential role of in situ gas chromatographic measurements in the future cometary, planetological and prebiotic chemistry studies.  相似文献   

10.
A 10-cm aperture telescope equipped with coronagraphic capabilities, using occulting masks of various size and material, has been developed to obtain low-light-level, wide-angle (~7o FOV), narrow-band filtered images of sodium exospheres at Io, the Moon and Mercury. Here we describe new instrument capabilities and recent findings about the extraordinarily long tails of sodium gas discovered in the lunar and hermean exospheres. Spatial and temporal variability patterns captured in such images can be used to study changes in surface sputtering processes and radiation pressure acceleration effects in the inner solar system.  相似文献   

11.
Cocks  F.H.  Watkins  S.A.  Walker  M.J.  Lutz  T.A.  Sussingham  J.C. 《Solar physics》2001,198(2):211-222
A telescope based upon dark-lens diffractive optics would be a uniquely new instrument for solar astronomy. The image formation process in such a telescope gives an intrinsically higher resolving power and a greatly reduced image intensity compared to that of refracting or reflecting optical systems of similar lens dimension. This low image intensity would be an advantage for solar observations made using a very large imaging element. After a brief overview of the history of solar instrument development, a quantitative evaluation of the dark-lens diffracting solar telescope concept is presented, showing the potential of this imaging method to meet or even to exceed the most demanding resolution goals currently being considered for future space-borne solar telescopes.  相似文献   

12.
A Stokes polarimeter has been built at the High Altitude Observatory to obtain line profiles in both linear and circular polarization in solar spectral lines. These measurements are interpreted using the theory of radiative transfer in the presence of a magnetic field to obtain vector magnetic fields on the solar disk and using the theory of resonance scattering and the Hanle effect to obtain vector magnetic fields in prominences. The polarimeter operates on the Sacramento Peak Observatory 40 cm coronagraph. It is an extensively modified and improved version of an earlier instrument.Polarization modulation is achieved by two KD*P Pockels cells at the coronagraph prime focus and demodulation is by a microprocessor. The instrument control and data handling is done by a minicomputer. Silicon photodiode 128 element line array detectors have replaced the two photomultipliers used on the earlier instrument. This gives a speed increase of a factor of 50.A polarization scrambler provides a chop to a reference beam of unpolarized light by time scrambling the polarization of the solar beam. This device improves sensitivity to polarizations less than 0.01%. The polarization measurements are photon noise limited in most cases. This noise is 0.1% for a typical three second observation which is about one gauss on the longitudinal field and 10 gauss on the transverse field.The National Center for Atmospheric Research is sponsored by The National Science Foundation.  相似文献   

13.
We consider the possibility of the excitation of sodium resonance emission in cometary matter under solar radiation at a heliocentric distance of 5 AU, as was observed when a fragment of Comet Shoemaker-Levy 9 plunged into Jupiter. When the sodium emission is calculated, the multiple scattering in the cometary cloud is taken into account. We use a non-LTE radiative transfer code for a two-level model sodium atom. A comparison of the computed and observed Na I D emission line profiles allows the column density of the sodium atoms for specific times of observations of Comet Shoemaker-Levy 9 to be determined. The observed Na I(D1+D2) line profile was found to agree well with the computed profile for an optically thick sodium cloud. We calculated the column density of the sodium atoms for three comets from the observed intensity of the D2 line emission. We also calculated the D2/D1 intensity ratio for various optical depths of the sodium cloud and various phase angles.  相似文献   

14.
Birmingham Solar Oscillations Network (BiSON) instruments use resonant scattering spectrometers to make unresolved Doppler velocity observations of the Sun. Unresolved measurements are not homogenous across the solar disc and so the observed data do not represent a uniform average over the entire surface. The influence on the inhomogeneity of the solar rotation and limb darkening has been considered previously and is well understood. Here, we consider a further effect that originates from the instrumentation itself. The intensity of light observed from a particular region on the solar disc is dependent on the distance between that region on the image of the solar disc formed in the instrument and the detector. The majority of BiSON instruments have two detectors positioned on opposite sides of the image of the solar disc and the observations made by each detector are weighted towards differing regions of the disc. Therefore, the visibility and amplitudes of the solar oscillations and the realization of the solar noise observed by each detector will differ. We find that the modelled bias is sensitive to many different parameters such as the width of solar absorption lines, the strength of the magnetic field in the resonant scattering spectrometer, the orientation of the Sun's rotation axis, the size of the image observed by the instrument and the optical depth in the vapour cell. We find that the modelled results best match the observations when the optical depth at the centre of the vapour cell is 0.55. The inhomogeneous weighting means that a 'velocity offset' is introduced into unresolved Doppler velocity observations of the Sun, which varies with time, and so has an impact on the long-term stability of the observations.  相似文献   

15.
E. Fossat  G. Ricort 《Solar physics》1973,28(2):311-317
Observations of the 300 s photospheric oscillation on large solar surfaces (up to 520 in diameter) using a sodium optical resonance cell seem to show that the power at long horizontal wavelengths is larger than previous results would indicate. In order to get more information about the spatial distribution of the energy, a new observational method has been perfected, which will allow us to obtain the spatiotemporal power spectrum.In some of our observations, a long-period oscillation (about 40 min) appears, with an amplitude comparable to that of the 300-s oscillation, and which seems to be correlated with the occurence of chromospheric flares.  相似文献   

16.
Seventeen comets, having information on sodium D-line emission during their apparition, have been studied. The heliocentric distances corresponding to the sodium emission commencement or termination epoch are found to have a dependence on the phase of the solar cycle. For comets appearing during a solar maximum the sodium emission is detectable out to greater distances than, for the comets appearing during solar minimum. The sodium emission is also found to depend on heliographic latitude of the comet. It is concluded that the spatial properties of the solar wind during a solar maximum and minimum are responsible for the observed dependence.  相似文献   

17.
The goals and construction details of a new design Polish-led X-ray spectrophotometer are described. The instrument is aimed to observe emission from entire solar corona and is placed as a separate block within the Russian TESIS X- and EUV complex aboard the CORONAS-PHOTON solar orbiting observatory. SphinX uses silicon PIN diode detectors for high time resolution measurements of the solar spectra in the range 0.8–15 keV. Its spectral resolution allows for discerning more than hundred separate energy bands in this range. The instrument dynamic range extends two orders of magnitude below and above these representative for GOES. The relative and absolute accuracy of spectral measurements is expected to be better than few percent, as follows from extensive ground laboratory calibrations.  相似文献   

18.
A design is presented for an instrument to measure solar oblateness without forming a solar image and having two identical prisms as the only optical elements. Feasibility calculations indicate that this might be sensitive and quite free from instrumental induced errors.  相似文献   

19.
We describe an instrument we have built and installed at Mees Solar Observatory on Haleakala, Maui, to measure polarization in narrow-band solar images. Observations in Zeemansensitive photospheric lines have been made for nearly all solar active regions since the instrument began operations in 1992. The magnetograph includes a 28-cm aperture telescope, a polarization modulator, a tunable Fabry-Pérot filter, CCD cameras and control electronics. Stokes spectra of a photospheric line are obtained with 7 pm spectral resolution, 1 arc sec spatial resolution over a field 4.7 arc min square, and polarimetric precision of 0.1%. A complete vector magnetogram observation can be made every eight minutes. The flexibility of the instrument encourages diverse observations: besides active region magnetograms we have made, for example, composite vector magnetograms of the full solar disk, and H polarization movies of flaring regions.  相似文献   

20.
We describe solar observations carried out for the first time jointly with Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) and Aalto University Metshovi Radio Observatory (MRO). KAIRA is new radio antenna array observing the decimeter and meter wavelength range. It is located near Kilpisjärvi, Finland, and operated by the SodankyläGeophysical Observatory, University of Oulu. We investigate the feasibility of KAIRA for solar observations, and the additional benefits of carrying out multi‐instrument solar observations with KAIRA and the MRO facilities, which are already used for regular solar observations. The data measured with three instruments at MRO, and with KAIRA during time period 2014 April–October were analyzed. One solar radio event, measured on 2014 April 18, was studied in detail. Seven solar flares were recorded with at least two of the three instruments at MRO, and with KAIRA during the chosen time period. KAIRA is a great versatile asset as a new Finnish instrument that can also be used for solar observations. Collaboration observations with MRO instruments and KAIRA enable detailed multi‐frequency solar flare analysis. Flare pulsations, flare statistics and radio spectra of single flares can be investigated due to the broad frequency range observations. The Northern locations of both MRO and KAIRA make as long as 15‐hour unique solar observations possible during summer time. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号