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1.
L. V. Ksanfomality 《Solar System Research》2011,45(4):281-303
The short exposure method proved to be very productive in ground-based observations of Mercury. Telescopic observations with
short exposures, together with computer codes for the processing of data arrays of many thousands of original electronic photos,
make it possible to improve the resolution of images from ground-based instruments to almost the diffraction limit. The resulting
composite images are comparable with images from spacecrafts approaching from a distance of about 1 million km. This paper
presents images of the hemisphere of Mercury in longitude sectors 90°–180°W, 215°–350°W, and 50°–90°W, including, among others,
areas not covered by spacecraft cameras. For the first time a giant S basin was discovered in the sector of longitudes 250°–290°W,
which is the largest formation of this type on terrestrial planets. Mercury has a strong phase effects. As a result, the view
of the surface changes completely with the change in the planetary phase. But the choice of the phase in the study using spacecrafts
is limited by orbital characteristics of the mission. Thus, ground-based observations of the planet provide a valuable support. 相似文献
2.
L. V. Ksanfomality 《Solar System Research》2008,42(6):451-472
Recent ground-based astronomical short-exposure observations of Mercury have yielded more than 50000 electronic pictures of the planet at different phases and different positions relative to the Earth. The work was fulfilled in several observatories. The use of available and newly developed processing methods applied to large volumes of electronic frames allowed the images of a considerable portion of Mercury’s surface to be synthesized. We present the images of the 90°–180°W, 215°–280°W, and 50°–90°W sectors containing, among others, the longitudes not covered by spacecraft imaging. Along with the listed images, we present the results of recent observations of Mercury carried out on November 20–24, 2006 during the morning elongation at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) (Nizhnii Arkhyz, Karachai-Circassia, the Caucasus). The 265°–350°W longitude sector of Mercury was observed. The observations were made under good weather conditions. Among the main tasks of the new observations was obtaining a complete view of the S Basin. Previously, this basin had been investigated in fragments only by the actual solar illumination conditions. During the period of November 20–24, 2006, the S Basin was on the sunlit side of the planet. The complete image of the basin was obtained from the processing of a large number of electronic frames. The appearance of the S Basin is compared with the data on its relief acquired with radar methods. In this longitude sector, a number of other unusual surface features were found; among them, are a huge “Medallion” crater and other formations. The results considered in the present and earlier published studies are compared with the Mariner 10 data (1974–1975) and with the data received from the Messenger spacecraft during its first flyby of the planet (January 2008). 相似文献
3.
Longitudinal distributions of the photospheric magnetic field studied on the basis of National Solar Observatory (Kitt Peak)
data (1976 – 2003) displayed two opposite patterns during different parts of the 11-year solar cycle. Helio-longitudinal distributions
differed for the ascending phase and the maximum of the solar cycle on the one hand and for the descending phase and the minimum
on the other, depicting maxima around two diametrically opposite Carrington longitudes (180° and 0°/360°). Thus the maximum
of the distribution shifted its position by 180° with the transition from one characteristic period to the other. Two characteristic
periods correspond to different situations occurring in the 22-year magnetic cycle of the Sun, in the course of which both
global magnetic field and the magnetic field of the leading sunspot in a group change their sign. During the ascending phase
and the maximum (active longitude 180°) polarities of the global magnetic field and those of the leading sunspots coincide,
whereas for the descending phase and the minimum (active longitude 0°/360°) the polarities are opposite. Thus the observed
change of active longitudes may be connected with the polarity changes of Sun’s magnetic field in the course of 22-year magnetic
cycle. 相似文献
4.
This paper presents the results of polarization observations of asteroid 554 Peraga obtained with the UBVRI polarimeter using
the 1.25 m telescope of the Crimean Astrophysical Observatory down to phase angles of 3.1°–16.6° from October to November
2006. The asteroid’s polarization phase curve is shown to have a negative branch with the parameters P
min = −1.7% and αmin = 8.4°, which is typical of C-type asteroids. However, these data contradict the results of Zellner and Gradie (1976) obtained
in March 1975 that the reflected light from the asteroid’s surface is positively polarized, ≈1% at phase angles of 8°–10°.
Since the asteroid’s ecliptic longitudes differ by 160°-145° for the two observation periods, we discuss the possibility that
the two sets of observations refer to the asteroid’s two hemispheres with different polarimetric properties. 相似文献
5.
We present resolved near-infrared spectra of Mercury scanning 70% of the surface in latitude and longitude from three separate observations, allowing us to perform a compositional investigation of its surface. By scanning the surface we find that all spectra in our sample are remarkably similar suggesting overall compositional homogeneity. We do, however, observe a slope difference between the spectra. These slope changes are most likely due to differences in the emission angle over different parts of the surface. We confirm the presence of a 1.1 μm feature that had been previously detected (Warell, J. et al. [2006]. Icarus 180, 281-291) and attributed to Ca-rich clinopyroxene. Finally, we investigated Mercury’s surface composition by comparing its spectrum with ground-based lunar spectra, lunar soil spectra collected in the laboratory, and analysis with a simple linear mixing model using various minerals as end-members. The result of this compositional investigation reveals that Mercury’s surface composition is likely to be quite different from the Moon’s. While low-Ca iron-rich pyroxenes are main surface components on the Moon (abundance varying from ∼5% to ∼35%), their abundance on Mercury may not exceed 5%. We also find that a Ca-rich clinopyroxene (in the hedenbergite-diopside series) is likely to be a main component of Mercury’s surface whereas this mineral is almost absent on the Moon. Our analysis also suggests the possible presence of olivine. We find that Mercury’s slope is less red than that of the Moon, in agreement with results from MESSENGER (McClintock, W.E., and 12 colleagues [2008]. Science 321, 62-65), and composition rather than variation of space weathering is likely the cause of this difference. 相似文献
6.
L. V. Ksanfomality 《Astronomy Letters》2005,31(11):767-785
We took electronic photographs of Mercury on the side of the planet that was not photographed from the Mariner-10 spacecraft in 1973–1975 by the millisecond-exposure method in ground-based observations. Based on these photographs, we synthesized resolved images of the surface of unknown regions of the planet. The capabilities of the method are limited by the small angular size of the planetary disk (only 7.3 arcsec at average quadrature), specific difficulties of Mercury’s ground-based observations, their very limited duration, and the laboriousness of the subsequent computer-aided observational data processing. The millisecond-exposure method is complex, but a sufficient number of primary electronic photographs can be taken under good seeing conditions for the subsequent synthesis of Mercurian images with a resolution of no worse than the diffraction limit. A giant basin about 2000 km in diameter and other large structures are distinguished in the synthesized images of the planet. In the regions where radar data are available, these structures can be identified with previously found ones. In some measure, the synthesized images allow the relief of the longitude sector 210°–290° W to be reconstructed on Mercury. It can be asserted with caution that the large relief features are distributed asymmetrically over the surface of Mercury, much as observed on other terrestrial planets, the Moon, and many satellites of giant planets. 相似文献
7.
A detailed study to evaluate ground-based photographs of Mercury has been carried out. Models of the surface scattering properties have been assumed and smeared with a Gaussian function for direct comparison with center-to-limb scans along Mercury's intensity equator. Data from a range of phase angles from 31° to 92° have been compared with smeared models assuming a Lambert surface, a surface which obeys the Lommel-Seeliger law and one which is Minnaertian, having a variable coefficient. Within the limits of the observations a lunar Minnaert surface yields the most consistent interpretation. An objective evaluation of the resolution of the photographs is obtained in terms of Gaussian half-widths. 相似文献
8.
For 181 PCA's recorded during the years 1956–1969 the association with flares is studied. Both the number of events which
cannot be associated with any flare on the visible hemisphere, as well as the longitude distribution of identified proton
flares, lead to the conclusion that 25–30% of PCA's are caused by flares behind the western solar limb. PCA's of this kind
are mostly small. During the investigated years no PCA > 13 dB and possibly no PCA > 8.5 dB were caused by flares behind the
limb, while hardly 60% of PCA's < l dB had their origin on the visible hemisphere.
While the sources of GLE's and of PCA's in general, are centered around 50°W which corresponds to the average curvature of
the magnetic field lines in interplanetary space, the strongest PCA's (> 8.5 dB) show an anomalous longitude distribution
centered around ∼ 20°W. It is suggested that this anomaly may be a consequence of the fact that in strong PCA events the kinetic
energy density of protons below 100 MeV becomes comparable to the magnetic energy density in space, thus leading to a ‘straightening’
of the magnetic field lines. 相似文献
9.
Deborah L. Domingue Faith Vilas Johan Warell Scott L. Murchie David T. Blewett Brian J. Anderson 《Icarus》2010,209(1):101-124
Disk-integrated and disk-resolved measurements of Mercury’s surface obtained by both the Mercury Dual Imaging System (MDIS) and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft were analyzed and compared with previous ground-based observations of Mercury at 11 wavelengths. The spectra show no definitive absorption features and display a red spectral slope (increasing reflectance with increasing wavelength) typical of space-weathered rocky surfaces. The MDIS spectra show evidence of phase reddening, which is not observed in the MASCS spectra. The MDIS spectra are commensurate with ground-based observations to within 10%, whereas the MASCS spectra display greater discrepancies with ground-based observations at near-infrared wavelengths. The derived photometric calibrations provide corrections within 10% for observations taken at phase angles less than ∼100°. The derived photometric properties are indicative of a more compact regolith than that of the lunar surface or of average S-type asteroids. The photometric roughness of the surface is also much smoother than the Moon’s. The calculated geometric albedo (reflectance at zero phase) is higher than lunar values. The lower reflectance of immature units on Mercury compared with immature units on the Moon, in conjunction with the higher geometric albedo, is indicative of more complicated grain structures within Mercury’s regolith. 相似文献
10.
H. S. Sawant R. Ramesh J. R. Cecatto C. Faria F. C. R. Fernandes R. R. Rosa M. C. Andrade S. Stephany L. B. T. Cividanes C. A. I. Miranda L. C. L. Botti J. W. S. V. Boas J. H. Saito C. E. Moron N. D. Mascarenhas K. R. Subramanian M. S. Sundararajan E. Ebenezer M. R. Sankararaman 《Solar physics》2007,242(1-2):213-220
An East – West, one-dimensional radio interferometer array consisting of five parabolic dish antennas has been set up at Cachoeira
Paulista (longitude 45°0′20″ W, latitude 22°41′19″ S) for observations of the Sun and some of the strong sidereal sources
by the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil. This is Phase-I of the proposed Brazilian Decimetric Array
and can be operated at any frequency in the range 1.2 – 1.7 GHz. The instrument has been in operation since November 2004
onwards at 1.6 GHz. The angular and temporal resolutions at this frequency are ∼3′ and 100 ms, respectively. Details of the
array, analog/digital receiver system, and a preliminary East – West one-dimensional solar image at the 1.6 GHz are presented
in this paper. 相似文献
11.
V. G. Kaydash S. Yu. Gerasimenko Yu. G. Shkuratov N. V. Opanasenko Yu. I. Velikodsky V. V. Korokhin M. V. Kaydash 《Solar System Research》2010,44(4):267-280
From the ground-based colorimetry performed for two surface regions of the near side of the Moon, images of the phase ratio
of the color index C(600 nm/470 nm) have been built for the phase angles between 2° and 95°. It has been found that for phase angles smaller than
α ∼ 40°–50°, the color index of the highlands grows with the phase quicker than that of the mare regions. For larger phase
angles, α > 50°, a reverse situation is observed. The laboratory data on the spectrophotometry of the lunar samples confirm
the peculiarities found in the phase dependence of color. The influence of multiple scattering on the phase dependence of
the color of the mare and highland regions of the Moon are discussed. 相似文献
12.
We amassed statistics for quiet-sun chromosphere spicules at the limb using ground-based observations from the Swedish 1-m Solar Telescope on La Palma and simultaneously from NASA’s Transition Region and Coronal Explorer (TRACE) spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond resolution obtained after maximizing
the ground-based resolution with the Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained specific statistics
for sizes and motions of over two dozen individual spicules, based on movies compiled at 50-second cadence for the series
of five wavelengths observed in a very narrow band at Hα, on-band and at ± 0.035 nm and ± 0.070 nm (10 s at each wavelength)
using the SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from TRACE. The MOMFBD restoration also
automatically aligned the images, facilitating the making of Dopplergrams at each off-band pair. We studied 40 Hα spicules,
and 14 EUV spicules that overlapped Hα spicules; we found that their dynamical and morphological properties fit into the framework
of several previous studies. From a preliminary comparison with spicule theories, our observations are consistent with a reconnection
mechanism for spicule generation, and with UV spicules being a sheath region surrounding the Hα spicules. 相似文献
13.
The global distribution of solar surface activity (active regions) is apparently connected with processes in the convection
zone. The large-scale magnetic structures above the tachocline could in a pronounced way be observable in the surface magnetic
field. To get the information regarding large-scale magnetic formations in the convection zone, a set of solar synoptic charts
(Mount Wilson 1998 – 2004, Fe i, 525.02 nm) have been analyzed. It is shown that the longitudinal dimensions and dynamics of supergiant complexes of solar
surface activity carry valuable information about the processes in the convection zone of the Sun. A clear effect of large-scale
(global) turbulence is found. This is a ‘fingerprint’ of deep convection, because there are no such large-scale turbulent
eddies in the solar photosphere. The preferred scales of longitudinal variations in surface solar activity are revealed. These
are: ∼ 24° (gigantic convection cells), 90°, 180° and 360°. 相似文献
14.
J. Hpfner 《Astronomische Nachrichten》1983,304(5):265-275
In 1980/1981 astronomical observations using a carried DANJON -astrolabe were made at Irkutsk, Potsdam and Simeiz stations in order to determine the longitude and latidute differences. — It is informed about the observations made and the analysis of the results obtained. The formulas required for the astronomical longitude and latitude determination are indicated. Subsequent calculation of the weighted mean serves to stepwise condence the values and, at the same time, to examine them for systematic groupe differences and personal errors. Finally the longitude and latitude differences are derived taking into account the observers' personal equations. Their accuracies range from ±0.0020 s to ±0.0028 s and from ±0.013”︁ to ±0.017”︁, respectively. Russian text ingnor 相似文献
15.
A. N. Abramenko G. V. Baida A. V. Zakrevskii L. G. Karachkina V. V. Prokof’eva-Mikhailovskaya E. A. Sergeeva 《Bulletin of the Crimean Astrophysical Observatory》2011,107(1):113-121
Photometric observations of Jupiter’s moons Io and Europa in the spectral band V have been made at the Crimean Astrophysical
Observatory for four years in order to construct their light curves reduced to a Solar phase angle of 6°. Comparison of these
data with other ground-based observations shows good agreement. This study confirms why the moons that are close to Jupiter
have a brighter leading hemisphere. The trailing hemispheres of Io and Europa, which are located in the rapidly rotating magnetic
field of Jupiter, are exposed to bombardment by charged particles of the magnetic field. Leaving out of consideration the
differences in brightness between the two hemispheres results in serious discrepancies between the space and ground-based
photometry data. 相似文献
16.
Y. V. Bogdanova C. J. Owen G. Siscoe A. N. Fazakerley I. Dandouras O. Marghitu Z. Kaymaz H. Rème E. A. Lucek 《Solar physics》2007,244(1-2):201-232
We present a study of the magnetospheric cusp response to extreme external parameters during passage of the ICME over the
Earth on 10 November 2004, based on Cluster observations of the plasma properties inside the low-latitude boundary layer (LLBL)/cusp regions. Two separate events are
observed while Cluster is in the dawn sector, 07 – 08 h magnetic local time (MLT). First, a LLBL/cusp crossing occurs during a period of strong
southward IMF. During this time, the LLBL/cusp is very small, ∼0.8 – 1° invariant latitude (ILAT) and moves equatorward, down
to 67° ILAT. This can be explained by the occurrence of significant magnetopause erosion due to enhanced dayside sub-solar
reconnection. The energy of the plasma inside this region is higher than normal, and the low-energy cut-off often observed
in the ion data is also unusually high. This might be explained by the suggestion that the local magnetosheath Alfvén velocity
and deHoffmann – Teller velocity are also both extremely high. However, the plasma convection and parallel velocity inside
this region are not very high. The second event discussed in this paper is a LLBL/cusp crossing during strong equatorial IMF
(mostly due to the dominant dawn – dusk component). Under these conditions, occurring at the same time as pulses of solar
wind dynamic pressure, the observations are very complicated. However, we suggest that in the polar region of the southern
hemisphere, Cluster cross two LLBLs/cusps, spatially separated by polar cap plasma. The first LLBL/cusp is formed by anti-parallel reconnection
in the dusk sector of the southern hemisphere and the second is formed by anti-parallel reconnection in the dawn sector of
the northern hemisphere. The second LLBL/cusp is located at extremely low latitude, less than ∼66.3° ILAT. During all LLBL/cusp
crossings, strong ionospheric O+ ion outflow is detected in the form of a narrow beam with limited pitch-angle range. 相似文献
17.
The activity of the Lyrid meteor shower is analyzed by visual observations in the interval 1900–2007. Processing of observations
over a long time interval confirmed the presence of two periods of activity of the shower, of 12 and 60 years. These periods
almost coincide with the period and five times Jupiter’s orbital period, i.e., 11.8 and 59.3 years, respectively, suggesting
the possible influence of Jupiter on the shower structure. High activity of the shower is observed when the epoch of observations
and the commensurate moment coincide with the orbital period of Jupiter and can be registered in the next 1–2 years. The increased
activity of Lyrid by visual observations suggests that ZHR exceeds 30 meteors per hour. The modeling of activity profiles of showers for different minimum masses of meteoroids has
shown that there is a correlation between the longitude of the node from the orbit with the mass of particles. 相似文献
18.
Starting with a large number (N=100) of Wind magnetic clouds (MCs) and applying necessary restrictions, we find a proper set of N=29 to investigate the average ecliptic plane projection of the upstream magnetosheath thickness as a function of the longitude
of the solar source of the MCs, for those cases of MCs having upstream shock waves. A few of the obvious restrictions on the
full set of MCs are the need for there to exist a driven upstream shock wave, knowledge of the MC’s solar source, and restriction
to only MCs of low axial latitudes. The analysis required splitting this set into two subsets according to average magnetosheath
speed: slow/average (300 – 500 km s−1) and fast (500 – 1100 km s−1) speeds. Only the fast set gives plausible results, where the estimated magnetosheath thickness (ΔS) goes from 0.042 to 0.079 AU (at 1 AU) over the longitude sector of 0° (adjusted source-center longitude of the average magnetic
cloud) to 40° off center (East or West), based on N=11 appropriate cases. These estimates are well determined with a sigma (σ) for the fit of 0.0055 AU, where σ is effectively the same as
(chi-squared) for the appropriate quadratic fit. The associated linear correlation coefficient for ΔS versus |Longitude| was very good (c.c.=0.93) for the fast range, and ΔS at 60° longitude is extrapolated to be 2.7 times the value at 0°. For the slower speeds we obtain the surprising result that
ΔS is typically more-or-less constant at 0.040±0.013 AU at all longitudes, indicating that the MC as a driver, when moving close
to the normal solar wind speed, has little influence on magnetosheath thickness. In some cases, the correct choice between
two candidate solar-source longitudes for a fast MC might be made by noting the value of the observed ΔS just upstream of the MC. Also, we point out that, for the 29 events, the average sheath speed was well correlated with the
quantity ΔV[=(〈V
MC〉−〈V
UPSTREAM〉)], and also with both 〈V
MC〉 and 〈V
MC,T〉, where 〈V
MC〉 is the first one-hour average of the MC speed, 〈V
MC,T〉 is the average MC speed across the full MC, and 〈V
UPSTREAM〉 is a five-hour average of the solar wind speed just upstream of the shock. 相似文献
19.
On the basis of the data from ground-based polarimetric, photometric, and other observations, as well as from space measurements (Mariner 10), we survey the investigations of the properties and peculiarities of Mercury's regolith in detail. We also present the results of our own observations performed during three apparitions of the planet in 2000–2002. An analysis of the published data points to essentially more intensive maturation processes in the Hermean surface regolith compared to that on the lunar surface. In addition, the orbital characteristics of Mercury allow us to suppose that the intensity of its regolith maturation and, therefore, the optical properties of its surface can noticeably depend on the planetocentric longitude. Polarimetric observations of Mercury's surface (the planetocentric longitude range was 265°–330°) carried out in 2000–2002 with a 70-cm reflector actually detected a polarization degree varying with an amplitude of about 1.5%. To ascertain the nature of these variations, additional observations of Mercury in a maximally wide range of planetocentric longitudes of the viewed surface are required. 相似文献
20.
Employing the synoptic maps of the photospheric magnetic fields from the beginning of solar cycle 21 to the end of 23, we
first build up a time – longitude stackplot at each latitude between ±35°. On each stackplot there are many tilted magnetic
structures clearly reflecting the rotation rates, and we adopt a cross-correlation technique to explore the rotation rates
from these tilted structures. Our new method avoids artificially choosing magnetic tracers, and it is convenient for investigating
the rotation rates of the positive and negative fields by omitting one kind of field on the stackplots. We have obtained the
following results. i) The rotation rates of the positive and negative fields (or the leader and follower polarities, depending on the hemispheres
and solar cycles) between latitudes ±35° during solar cycles 21–23 are derived. The reversal times of the leader and follower
polarities are usually not consistent with the years of the solar minimum, nevertheless, at latitudes ±16°, the reversal times
are almost simultaneous with them. ii) The rotation rates of the three solar cycles averaged over each cycle are calculated separately for the positive, negative
and total fields. The latitude profiles of rotation of the positive and negative fields exhibit equatorial symmetries with
each other, and those of the total fields lie between them. iii) The differences in rotation rates between the leader and follower polarities are obtained. They are very small near the
equator, and increase as latitude increases. In the latitude range of 5° – 20°, these differences reach 0.05 deg day−1, and the mean difference for solar cycle 22 is somewhat smaller than cycles 21 and 23 in these latitude regions. Then, the
differences reduce again at latitudes higher than 20°. 相似文献