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1.
Image restoration from modulated intensities can be performed by directly solving the intensity modulation equation. This method of producing images does not rely on position sensitive detector. Computer simulation results for space low-energy-ray imaging show that images with fine angular resolution within a wide field of view can be obtained by simple collimated devices.  相似文献   

2.
It is proved that a periodic orbit of the three-dimensional circular restricted three-body problem can be continued analytically, when the mass of the third body is sufficiently small, to a periodic orbit of the three dimensional general three-body problem in a rotating frame. The above method is not applicable when the period of the periodic orbit of the restricted problem is equal to 2k (k any integer), in the usual normalized units. Several numerical examples are given.  相似文献   

3.
High resolution reconstruction of complicated objects from incomplete and noisy data can be achieved by solving observational modulation equations or correlated modulation equations iteratively under physical constraints. Simulations and experiments show that wide field and high resolution images of space hard X-rays and soft -rays can be obtained by scan observation of a collimated non-position-sensitive detector.  相似文献   

4.
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   

5.
It has been shown by Atkinson (1965) that there is a rigorously exact euclidean interpretation of the general relativity field equations if certain arbitrary definitions of mass (m0 and the velocity of light (c) are invoked. With a preferred (euclidean) frame postulatedab initio, a particularly simple explanation in terms of classical physics may be found for very similar definitions ofm andc. It is not unexpected that with this scheme, all the usual tests of general relativity (light deflexion, perihelion motion, gravitational redshift, and radar delay time) are immediately satisfield. The preferred frame is however identified with a real aether and this requires a return to the Lorentzian interpretation of the special relativistic transformations of space and time variables. It is shown that gravity may be attributed to the action of a temperature gradient in the aether and an explanation of its origin in terms of an ideal relativistic gas is proposed. The temperature gradients are thermodynamically stable and do not diffuse if the relativistic aether ( A ) is effectively adiabatic and matter is fundamentally a species of aether with instantaneous motion at high (> A ) relative to the aethereal reast frame. To be consistent with such a picture, it is necessary to assume aether particles are capable of forming temporary associations (not recognized as matter) which take on some of the properties of crystalline solids and thereby become the means of transmitting electromagnetic radiation through space. The aether is essentially treated as a virtually incompressible fluid in which the pressure at any point arises from both random (temperature) and bulk (high ) motions. A number of specific predictions arising from this theory of gravity are indicated and these may serve to discriminate it from general relativity.  相似文献   

6.
Exploring one of the most pristine bodies in our solar system — a comet — with a spacecraft will be a great step towards a deeper understanding of our solar system's beginnings. We here present the advanced space experiment CoMA (cometarymatteranalyzer), which will be flown on NASA's cometary rendezvous and asteroid flyby mission CRAF. CoMA is a high resolution time-of-flight secondary ion mass spectrometer. It will analyze m-sized cometary dust grains and cometary gases with an unprecedented mass resolution and will yield data about the elemental, isotopic, and molecular composition.  相似文献   

7.
We present a new method to separate interplanetary and coronal propagation, starting from intensity variations observed by spaceprobes at different heliolongitudes. In general, a decrease in absolute intensities is observed simultaneously with an increase in temporal delays. The coupling of these two effects can be described by Reid's model of coronal diffusion and can in principle be used to determine the two coronal time constants, diffusion time t c and escape time A. In addition, a least-squares fit method is used to determine the parameters of interplanetary transport, assuming a radial dependence as (r) = 0(r/1 AU)b. The method is applied to the two solar events of 27 December, 1977 and 1 January, 1978 which were observed by the spaceprobes Helios 1, Helios 2, and Prognoz 6. Energetic particle data are analysed for 13–27 MeV protons and -0.5 MeV electrons. For the regions in space encountered during these events the mean free path of electrons is smaller than that of protons. Straight interpolation between the two rigidities leads to a rather flat rigidity dependence (P) P n with n = 0.17–0.25. This contradicts the prediction of a constant mean free path or of the transition to scatter-free propagation below about 100 MV rigidity. In three of the four cases the mean free path of 13–27 MeV protons is of the order 0.17 AU, the mean free path of electrons of the order 0.06 AU. For protons we find b - 0.7 for the exponent of the radial variation.The concept of two different coronal propagation regimes is confirmed. It is remarkable that in both regimes electrons are transported more efficiently than protons. This holds for the temporal delay as well as for the amplitude decrease. This is in contrast with the long existing concept of rigidity independent transport and puts severe limits to any model of coronal transport. For the December event all three spaceprobes are in the fast propagation regime up to an angular distance of 62°. For protons we find a finite delay even in the fast propagation region, corresponding to a coronal delay rate of about 0.8 hr rad-1 up to 60° angular distance. In contrast, relativistic electrons may reach this distance within a few minutes.The fast transport of electrons and the different behaviour of electrons and protons is in contradiction to the expanding bottle concept. An explanation of coronal transport by shock acceleration directly on open field lines could in principle work in case of protons in the fast propagation region, but would fail in case of the electrons. The fast and efficient transport of electrons is most likely due to a region of field lines extending over a wide range of longitudes directly from the active region into interplanetary space. The much slower transport of both particle types at large azimuthal distances can neither be explained by direct access to open field lines not by the direct shock acceleration concept. A possible explanation is the loop reconnection model in a modified version, allowing for a faster lateral transport of electrons.Now at AEG, 2000 Wedel, F.R.G.  相似文献   

8.
F. Kneer  F. Stolpe 《Solar physics》1996,164(1-2):303-310
This contribution deals with the properties of small-scale magnetic elements in plages. Spectro-polarimetric observations, obtained with the highest possible spatial resolution with the German solar telescopes at the Observatorio del Teide on Tenerife, were analysed. We conclude from the spread of line parameters measured in the Stokes I and V profiles of Fe I and Fe II lines that a wide range of magnetic properties is realised in the solar atmosphere. The flow velocities in small-scale magnetic flux tubes, deduced from the zero-crossing of the V profiles at high spatial resolution, show a fluctuation of v Doppler = 580 m s-1. This is substantially smaller than the turbulent broadening velocities of v Doppler = 2 – 3 km s–1 commonly derived by fitting V profiles from flux tube models to low spatial resolution data, e.g. from a Fourier Transform Spectrometer. Attempts to explain the high resolution I and V profiles by models of hydrostatic flux tubes are discussed. It appears impossible to accomplish agreement between the modeled and observed radiation of lines with strong and weak magnetic sensitivity at the same time. We suggest a scenario in which small-scale magnetic elements possess substructure and are dynamic, with gas flows and magnetic field strengths varying in space and time.  相似文献   

9.
High resolution surveys of the galactic centre suggest the existence of an extended nonthermal source (Bulge) with an intensity much larger than the total background radiation in that direction. In this paper, we have first evaluated the physical conditions existing in this restricted region of space from an analysis of the radio spectrum and shown that if the distribution of matter, magnetic fieldB(r) and cosmic ray densityk(r) in the plane of the Galaxy is of gaussian type then at the centreB (0)=25–30 G andk(0)=25–35 times that in the near interstellar space. It is also found that most of the absorption in the Sagittarius A spectrum at low frequencies takes place in the Bulge and one requires a small additional absorption to take place in the line of sight corresponding to n e 210 cm–6 pc at a temperature typically of clouds 100 K. The gamma ray spectra from the Bulge arising from interactions of cosmic rays with matter and radiation are then calculated in detail. A comparison made with the estimated background gamma ray spectra from the disk reveals that a detector with angular resolution 6° having a threshold of a few times 10–6 photons cm–2 s–1 can detect this source; this bulge is not found to be a good X-ray source for detection. From a comparison of these calculations with the observed flux above 100 MeV, the following inferences have been deduced: (i) the lower limit to the magnetic field strength at the centre is 12 G, (ii) the observed gamma ray flux towards the Anti-centre can be well explained as due to interactions of cosmic rays with matter alone and a similar explanation towards the center reveals that cloud complexes could be more in the inner parts of the Galaxy than in the outer parts, and (iii) the observed flux values are found to be inconsistent with the existence of submillimeter radiation in the galactic scale.  相似文献   

10.
We study a new indirect index, or proxy data, of the solar activity - the intensity of luminescence of the microzones of cave flowstones. This index is in anticorrelation with the index deposition rate of 14C and in direct correlation with the solar activity as in thermoluminescent time series of sediment cores. Luminescence time series was obtained for long time intervals with different time resolution (from 5 years per pixel to 5 pixels per year). In such time series the long minima of Maunder and Spoerer, the Medieval maximum and other well known long lasting minima and maxima as well as some new ones can be seen. The very good resolution permits to study the general statistical properties of past solar activity. Some of the results obtained refer to the problem of the mechanism of solar magnetic field generation.  相似文献   

11.
The Caledonian four-body problem introduced in a recent paper by the authors is reduced to its simplest form, namely the symmetrical, four body double binary problem, by employing all possible symmetries. The problem is three-dimensional and involves initially two binaries, each binary having unequal masses but the same two masses as the other binary. It is shown that the simplicity of the model enables zero-velocity surfaces to be found from the energy integral and expressed in a three dimensional space in terms of three distances r 1, r 2, and r 12, where r 1 and r 2 are the distances of two bodies which form an initial binary from the four body systems centre of mass andr 12 is the separation between the two bodies.  相似文献   

12.
The Transient Gamma-Ray Spectrometer (TGRS) was launched aboard the GGS/WIND spacecraft on November 1, 1994. After several deep space orbits (2 yrs) WIND will eventually be injected into a halo orbit around the Sun-EarthL 1 point. TGRS consists of a 215 cm3 high purityn-type Ge crystal which is kept at cryogenic temperatures by a passive radiative cooler. The energy range covered by the instrument is 25–8000 keV with an energy resolution of 2–3 keV. The primary task of TGRS is to perform high resolution spectroscopy of gamma-ray bursts and solar flares. Additional objectives are the study of transient x-ray pulsars and, using an on-board passive occulter, the long-term monitoring of sources such as the Crab and the Galactic Center. Since launch, TGRS has been performing exceedingly well, and all the important experiment parameters such as background levels, gain, and resolution have proven to be very stable. To date, TGRS has detected 27 GRBs and three solar flares. Preliminary analysis of our data also indicates that TGRS is indeed sensitive to sources such as the Crab and the Galactic Center.  相似文献   

13.
Recent observational and theoretical studies of the structure of umbral chromosphres have led us to propose new models of the region. We combine space and ground based determinations of the densitytemperature structure of the transition region with existing Caii H, K, and IR triplet spectral data to establish relatively high density, gradient models of the sunspot chromosphere.Avrett in 1981 presented theSunspot Sunspot Model which can be characterized as a physically extended, low density, plateau model. However, in a similar study, the authors (Beebeet al., 1982) pointed out that the relatively high transition region pressures derived from space observations indeed are required to reproduce high resolution Caii spectral features. Studies of the umbral chromosphere as a resonant cavity for slow-mode magneto-acoustic waves producing umbral oscillations (Zhugzhdaet al., 1984) also lead to atmospheres of relatively small physical thickness, thus higher densities.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

14.
Snapshot spectroscopic imagers/instruments (SSI) are a class of spectroscopic instruments that are capable of acquiring spectral information of a given field of view in a single frame. Standard spectroscopic instruments like a grating-based spectrograph or a Fabry–Pérot-based spectrograph obtain two dimensional data of 2D space or 1D space and 1D wavelength. But SSIs have three dimensional data of 2D space and wavelength embedded in two dimensional detector/image plane. So standard data reduction techniques are not applicable. Lenslet array spectroscope is a novel SSI which images the object on to a hybrid spatio-spectral image plane. A procedure to extract the spatial and spectral information of the field of view from this hyperplane is presented. We demonstrate the snapshot capabilities of this instrument to study dynamic activities of the Sun as inferred from two measurements: (i) Evershed flow in a sunspot in NOAA 12526 at Fe?i 6301.5 Å and (ii) oscillations in a quiescent prominence at H\(\upalpha \) 6562.8 Å. This instrument can be used for large or small scale structures, making it efficient for studying a wide range of dynamic activities like helioseismology, Moreton waves, prominence oscillation etc.  相似文献   

15.
Fine structure of solar magnetic fields   总被引：2，自引：0，他引：2  
The deduction of magnetic fields from chromospheric structure is extended to active regions and transverse fields. Fields independently predicted by these rules from a high resolution H filtergram are compared with a high resolution magnetogram. The H method has the advantage over conventional magnetograms that it shows transverse fields and relates the fields to the real Sun. It has the disadvantage that higher spatial resolution is required and that it is difficult and time consuming in very complicated regions.The response of the chromosphere to magnetic fields is most consistent. Vertical field is invariably marked by bright plage, with brightness roughly proportional to the field strength (except for sunspots). All dark fibrils mark transverse fields and are parallel to field lines. All polarity changes are marked by dark fibrils, which may be transverse fibrils perpendicular to the field boundary, or filaments (prominences) which connect more distant points, and in which the field lines run nearly parallel to the boundary. The asymmetry between preceding and following polarity found by Veeder and Zirin (1970) does not exist; it was due to the low resolution of the Mount Wilson magnetograms.The complexity of active region field structure depends on the history of the region; all flux erupts in simple bipolar form, and lines of force remain connected to sibling spots until reconnection takes place. Thus the complex structure only occurs after eruption of several dipoles which reconnect. The phenomenon of inverted polarity turns out to be due to the emergence of satellite bipolar fields, where the p spot merges with the rest of the p field and the f spot appears as an included f field. Flares usually occur when the field lines from f spot reconnect from its sibling to the main spot.  相似文献   

16.
The possible occurrence of luminescence emission by different irradiated materials in interstellar space is discussed. It is shown by means of a model computation that the quantum efficiency of luminescence emission is high enough and can, in general, be detected in interstellar space. Further, it is argued that the wavelength-dependent intensity increase observed in the NGC 7023 reflection nebula at the distance of 3.4 from the illuminating star can be explained by luminescence emission of UV irradiated and Cu or rare-earth-doped glassy particles.  相似文献   

17.
A multiplexX-ray image analyser is described. It consists in a time-modulated coded aperture associated with a solid state detector. The system combines the high efficiency and good spectral resolution of solid state spectrometers with the spatial resolution of the coded aperture (200 ).The device can be installed at the focus of a grazing incidence telescope to make images and spectra of faint astronomicalX-ray sources.  相似文献   

18.
When spectra of the daytime sky are compared with those directly from the Sun, it is found that the depths of the Fraunhofer lines are reduced. This indicates the presence of an added light, the Ring effect. Most previous research on the Ring effect has been performed spectroscopically, with the notion that the added component is always unpolarized. Here we presented spectropolarimetric observations using the principle of the line depth method (compression between the line centre and its continuum) to investigate this effect. The general scattered light of the blue sky is polarized and as the additional component may or may not also be polarized, the filling-in effect should be detectable by performing spectropolarimetry, which indeed has been achieved. The observations have involved the use of high precision polarimetry with spectral resolution 2 Å at the H Fraunhofer spectral line. The data indicate a variation of the linear polarization in the H line centre as a function of the solar zenith angle. One possible advantage of the polarimetric technique is that the Ring effect detections can be made without recourse to solar measurements directly or indirectly using an attenuator. Finally, a model without knowledge of the filling-in mechanism, has yielded a good qualitative agreement with the observational behaviours and it can be taken as a first step to explain the variation of the linear polarization across the spectral line.  相似文献   

19.
A new set of photoelectric B and V observations of W Ursae Majoris obtained during a period of one week in 1968 is presented.From the measurements it can be concluded that in general the light curve in both colors is free from complications. In particular, no systematic brightness differences between consecutive periods can be found.The observations made during total eclipse in two different periods yield flat minima fitting almost perfectly together, the mean error of the single measurement beeing of the order of 0.m003. The duration of the phase of totality is estimated to 0.036P=17.3 m thus confirming the value given by Cester and Gridelli.From a plot of the square deviations of the single observations (I/I)2 from the mean intensity curve vs phase it can be shown that the scattering decreases strongly during primary eclipse thus indicating that the source producing these fluctuations is essentially confined to the space between the two components. A comparison with earlier photoelectric observations also supports the assumption that the variational behavior of the light curve is caused by a gaseous cloud between the two components rather than by an envelope surrounding the whole system.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

20.
The dynamic spectrum, a three dimensional record of the radio intensity as a function both of time and frequency, has long been used as a probe of plasma processes in the solar corona. Beginning with the work of Wild and McCready (1950) dynamic spectroscopy has been used to distinguish between the multitude of radio wave emitting phenomena which occur in the solar corona and to infer the physical mechanisms responsible.Stellar dynamic spectroscopy has always been a tantalizing prospect. The vast body of experience with solar dynamic spectroscopy would prove invaluable in interpreting stellar dynamic spectra. Further, the new parameter regimes presented by stellar coronas would allow further insight to be gained in the physical processes at work in stellar coronas.Recently, Bastian and Bookbinder (1987) used the Very Large Array in spectral line mode at 1.4 GHz with a bandwidth of 50 MHz to obtain the first dynamic spectra of nearby flare stars. The spectral resolution was 3.125 MHz and the temporal resolution was 5 s. While the relative bandwidth was less than ideal (/ 5%), the spectra so obtained were sufficient to show the presence of narrowband structure in a radio outburst from the well-known dMe flare star UV Ceti.Several efforts are now underway to obtain stellar dynamic spectra, of both RS CVn binaries and dMe flare stars, with higher degrees of spectral and temporal resolution. Among these are use of a 1024 channel correlator with the 1000' telescope at Arecibo and use of the Berkeley Fast Pulsar Search Machine (Kulkarni et al. 1984) with the Green Bank 140' telescope.
  相似文献   

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