共查询到20条相似文献，搜索用时 31 毫秒
1.
The purpose of this paper is to find correlation between OI 6300 Å line intensity with solar and ionospheric parameters. A critical study have been made and the following important results are obtained:
相似文献
| (i) | Solar flare index plays more important role for the emissions of 6300 Å line than other solar parameters. |
| (ii) | Intensity of 6300 Å line increases linearly with the increase of solar flare index. |
| (iii) | Virtual height plays more important role than critical frequency for the emission of 6300 Å line-intensity. |
| (iv) | Possible explanation of this type of variation is also presented. |
2.
Frank Hill 《Solar physics》1990,128(1):321-331
The first map of the horizontal flows as a function of depth and heliocentric position in the solar convection zone is presented. The map is inferred from a least-squares smoothness-constrained inversion of velocities measured from ring diagrams of the solar p-mode oscillations. The data provide information in four longitude regions at a latitude just south of the solar equator. The presence of several features is suggested by the results:
The magnitude of the flows is substantial, reaching some 450 m s–1 for the longitudinal jet, and 150 m s–1 for the latitudinal flow. Possible systematic errors and the physical consequences of the flows are discussed. 相似文献
| (1) | A prograde directed longitudinal jet between the hydrogen and first helium ionization zone, reversing direction to retrograde below the second helium ionization zone. |
| (2) | A equatorward directed latitudinal flow above the second helium ionization zone. |
| (3) | A poleward latitudinal flow below the second helium ionization zone, but only in one of the four longitude bands. A large active region was present in this band, but not in two of the other bands, suggesting a possible relationship between the activity and the different flow pattern. |
3.
K. B. Bhatnagar Usha Gupta Rashmi Bhardwaj 《Celestial Mechanics and Dynamical Astronomy》1994,59(4):345-374
The non-linear stability of the libration pointL
4 in the restricted problem has been studied when there are perturbations in the potentials between the bodies. It is seen that the pointL
4 is stable for all mass ratios in the range of linear stability except for three mass ratios depending upon the perturbing functions. The theory is applied to the following four cases:
相似文献
| (i) | There are no perturbations in the potentials (classical problem). |
| (ii) | Only the bigger primary is an oblate spheroid whose axis of symmetry is perpendicular to the plane of relative motion (circular) of the primaries. |
| (iii) | Both the primaries are oblate spheroids whose axes of symmetry are perpendicular to the plane of relative motion (circular) of the primaries. |
| (iv) | The primaries are spherical in shape and the bigger is a source of radiation. |
4.
J. H. Piddington 《Astrophysics and Space Science》1976,41(2):371-385
Using a combination of solar and interplanetary measurements, a topological model is developed of the overall magnetic and plasma structures.
相似文献
| (i) | The basic framework is the magnetic field, whose structure is found by combining measurements made at the photosphere, the transition region, and at 1 AU. It divides the atmosphere into three physically isolated regions having quite different processes of energy and plasma transfer, and very different properties. |
| (ii) | A magnetically open atmosphere is confined within 10% of the surface magnetic flux in the form of tiny nozzles. It expands from 0.1% of the photospheric area to 10% of the low corona and 100% of the solar wind. Energy absorption and resulting expansion is traced from chromospheric levels. |
| (iii) | A model of M-regions, high-speed plasma streams and interplanetary sector structure is based on refraction of acoustic waves and their focusing into the centres of sectors. |
| (iv) | The average magnetically enclosed atmosphere occupies1% of the photosphere, spreading to 90% of the low corona. Surface flux is concentrated into strands of 4×1018 Mx, with 30 per supergranule cell. The strands spread and also divide into smaller flux tubes to accout for chromospheric fine structure in which magnetic forces dominate. It is questionable that this complex of plasma elements should be called an atmosphere. |
| (v) | The third, non-magnetic part of the solar atmosphere comprises on averae 99% of the photosphere and a large part of the chromosphere (the network interior), but little if any of the corona. It is stressed that measurements or models of the solar atmosphere have little meaning unless they relate to a particular one of the three regions described here. |
| (vi) | It is confirmed that most of the energy needed to heat the solar atmosphere traverses the photosphere as Alfvén waves. Some energy is converted to acoustic waves at the boundaries of the magnetic fields, some is dissipated when the Alfvén waves become non-linear. |
5.
The paper presents the effect of O3 depletion on different night airglow emission lines. Calculations based on chemical kinetics show that the airglow intensity of Na5893Å, O5577Å and OH band emissions will also be affected due to the depletion of O3 concentration. Intensity of Na5893Å is calculated theoretically for Halley Bay (76° S,27° W), British Antarctic Survey Station, during the period 1973 to 1984. It is concluded from the covariation of different emission lines that O5577Å and OH emissions also follow the same trend of variation. A study has been made to find the correlation between the depletion of O3 concentration and total solar flare numbers. Important results are as follows:
相似文献
| (i) | Depletion of O3 is oscillatory upto 7932 solar flare numbers. The average trend of variation of O3 concentration is downward, i.e., O3 is depleted with the increase of total solar flare numbers. |
| (ii) | Afterwards, it follows a upward trend. Possible explanation of such type variation is also presented. |
6.
Douglas C. Heggie 《Celestial Mechanics and Dynamical Astronomy》1976,14(1):69-71
It has been shown (Heggie, 1974) that the equations of motion for the three-body problem may be cast into a form which is regular for collisions betweenany pair of bodies. The method proceeds by two stages, namely
The present contribution gives a different treatment of the first of these stages, and relates the redundant variables to those introduced by Broucke and Lass (1973). 相似文献
| (i) | the introduction of redundant variables |
| (ii) | the application of the KS-transformation. |
7.
XMM-Newton is a major X-ray observatory of the European Space Agency (ESA). Its observing time is open to astronomers from the whole scientific community on a peer reviewed competitive basis. The Science Operations Centre, located at ESA’s premises in Villafranca del Castillo, Spain, is responsible for the instrument operations, as well as for all the tasks related to facilitating the scientific exploitation of the data which the mission has been producing since its launch in December 1999. Among them, one may list:
Everyone can be an XMM-Newton observer. So far, astronomers from 36 countries submitted observing programs. Public data can be accessed by every scientist in the world through the XMM-Newton Science Archive (XSA).Despite all these efforts, one can’t help noticing an asymmetric level of scientific exploitation in the realm of X-ray astronomy between developing and developed countries. The latter have traditionally enjoyed the comparative advantage of deeper know-how, deriving from direct experience in hardware and mission development. The XMM-Newton Science Operations Centre’s efforts act to alleviate this situation through, for example, increasing the usage of the web for data and information dissemination, as well as by supporting actively such initiatives as the COSPAR Capacity-Building Workshops, specifically designed to create long-lasting bridges between researchers in developing and developed countries. 相似文献
| • | distribution of scientific data in different formats, from raw telemetry, up to processed and calibrated high-level science products, such as images, spectra, source lists, etc; |
| • | development and distribution of dedicated science analysis software, as well as of continuously updated instrument calibration; |
| • | regular organisation of training workshops (free of cost), for potential users of XMM-Newton data, where the procedures and techniques to successfully reduce and analyze XMM-Newton data are introduced; |
| • | access to the data through state-of-the-art, in-house-developed archival facilities, either through the Internet or via CD-ROM; |
| • | continuously updated documentation on all aspects of spacecraft and instrument operations, data reduction and analysis; |
| • | maintenance of a comprehensive set of project web pages; |
| • | a competent and responsive HelpDesk, providing dedicated support to individual XMM-Newton users. |
8.
In this paper we present new and exact analytical and computational developments of Güttler's formulae for composite grains, thereafter applied for the two models:
Literal and analytical expressions have been established for the Riccati-Bessel of the complex functions
n
,
n
, and
n
and their derivatives. The problem is treated in its general form without any restriction and the computer programme is now ready for request. 相似文献
| (1) | Graphite core-ice mantle. |
| (2) | Silicate core-ice mantle. |
9.
The main goal of this paper is to compare the relative importance of destruction by tides vs. destruction by mergers, in order to assess if tidal destruction of galaxies in clusters is a viable scenario for explaining
the origin of intracluster stars. We have designed a simple algorithm for simulating the evolution of isolated clusters. The
distribution of galaxies in the cluster is evolved using a direct gravitational N-body algorithm combined with a subgrid treatment of physical processes such as mergers, tidal disruption, and galaxy harassment.
Using this algorithm, we have performed a total of 148 simulations. Our main results are:
相似文献
| – | destruction of dwarf galaxies by mergers dominates over destruction by tides, and |
| – | the destruction of galaxies by tides is sufficient to explain the observed intracluster light in clusters. |
10.
Sergey M. Kudryavtsev 《Celestial Mechanics and Dynamical Astronomy》1995,61(3):207-215
A high-precise analytical theory of a satellite in orbit around a non-spherical planet has been developed. The Poisson's small parameter method has been used. All secular and short-periodic perturbations proportional up to and including a product of five arbitrary harmonic coefficients of the planetary potential expansion are calculated. Long-periodic perturbations are derived with the accuracy of up to the fourth-order, inclusive. The influence of the high-order perturbations on the motion of ETALON-1 satellite has been investigated. The results of comparison of the numerical and analytical integration of the equations of its motion over a five year interval are as follows:
The theory is intended to be used for processing precise laser range measurements of the Earth geodynamical satellites over long-term intervals. 相似文献
| – | - the r.m.s. difference between the positions is 1.1 cm; |
| – | - the r.m.s. difference between the ranges is 0.5 cm. |
11.
All-sunspots from September 1986 to December 1992 in solar cycle 22 are used to investigate the characteristics of-sunspots and the relationship between-sunspots and X-class X-ray flares. The main results of this statistical study are as follows.
相似文献
| (1) | The earlier discoveries on the formation and disintegration patterns of-sunspots (Tang, 1983; Zirin and Liggett, 1987; Zirin, 1988) are confirmed. In a general sense, all-sunspots form from the penetration of two different dipoles. Delta-sunspots could be disintegrated byin situ flux cancellation. In addition, some-sunspots become separated by the sliding apart of opposite polarities. |
| (2) | A prominent characteristic of-sunspots is the imbalanced flux between the two polarities. A sample of 58-sunspots observed by the Solar Magnetic Field Telescope at Huairou, in which there are one or more X-class flares, maintains an average flux ratio of 6.6 between the majority and minority polarities. Unlike the early results of Tang (1983), two-third of them show a dominant flux from the preceding spots. |
| (3) | The number of-sunspots seems to be an index of solar activity. More than 95% of X-class X-ray flares take place in active regions of-sunspots; while 23% of-sunspots are generators of X-class X-ray flares. The productivity of X-class flares is closely correlated to the lifetime of-sunspots in this manner:P xxf = –0.12 + 0.02T Emphasis>/2 . |
12.
A new method for computing potential magnetic field configurations in the solar atmosphere is described. A discrete approximation to Laplace's equation is solved in the domain R
r R
1, 0 , 0 2 (R
1being an arbitrary radial distance from the solar center). The method utilizes the measured line-of-sight magnetic fields directly as the boundary condition at the solar surface and constrains the field to become radial at the outer boundary, R
1. First the differential equation and boundary conditions are reduced to a set of two-dimensional equations in r, by Fourier transforming out the periodic dependence. Next each transformed boundary condition is converted to a Dirichlet surface condition. Then each two-dimensional equation with standard Dirichlet-Dirichlet boundary conditions is solved for the Fourier coefficient it determines. Finally, the solution of the original three dimensional equation is obtained through inverse Fourier transformation. The primary numerical tools in this technique are the use of a finite fast Fourier transform technique and also a generalized cyclic reduction algorithm developed at NCAR. Any extraneous monopole component present in the data can be removed if so desired.The code was developed for the HAO solar-interplanetary modeling effort in response to the following specific requirements:
相似文献
| (1) | High resolution. |
| (2) | Speed in computation. |
| (3) | Sufficiently accurate solutions of Laplace's equation at all heights. |
13.
Bernard R. Durney 《Solar physics》1989,123(2):197-216
The following points are discussed:
Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation. 相似文献
| (i) | The dependence of the angular velocity, , on the spatial coordinates near the lower boundary, R c, of the solar convection zone (SCZ) can be obtained from an integration with respect to r of a sound approximation to the azimuthal equation of motion. Here P 2 (cos ) is the second-order Legendre polynomial and is the polar angle. Estimates of 0, 2 (the primes denote derivatives with respect to r), based on the best available values for the Reynolds stresses and anisotropic viscosity coefficients, suggest that 0 < 0,=">2 0 for r = R c. Since a reliable theory of anisotropic turbulent coefficients does not exist at present, positive values of 0 are conceivable. |
| (ii) | In the lower SCZ the latitudinal variations of the superadiabatic gradient vanish if is constant along cylinders. The uniformity of the superadiabatic gradient is, however, inconsequential: the physically meaningful rotation law is the one that insures the uniformity of the convective flux. |
| (iii) | With the exception of the polar regions, the angular momentum transport in thin azimuthal convective rolls is towards the equator. |
| (iv) | It is suggested that buoyancy uncorrelates horizontally separated regions in the lower SCZ preventing the generation of magnetic fields with small wave numbers: in consequence, the cycle magnetic field must be generated in a region of weak buoyancy whereas the lower SCZ generates a weak rather stochastic magnetic field. The dependence on rotation of these two types of magnetic field could differ. |
| (v) | In the context of helioseismology it is customary to expand the perturbations (induced by rotation) of the eigenfrequencies in the following form: , where the notation is standard. The observations reveal that to a good approximation a 1 is independent of l. It is shown that this is the case if is constant with r. For a simple viscous, rotating fluid in the steady state (r) is constant with r if the angular momentum loss vanishes. Let J(ri dr) be the angular momentum of a thin shell of radius r and thickness dr. Since , the constancy of (r) implies that each shell of radius r has the same angular momentum as if the Sun were rotating uniformly with an angular velocity given by . It is discussed whether, alternatively, the observations simply indicate that 0(r) is a slowly varying function of r. |
14.
With the use of interplanetary coronal mass ejections (ICMEs) compiled by Richardson and Cane from 1996 to 2007 and the associated
coronal mass ejections (CMEs) observed by the Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric
Observatory (SOHO), we investigate the solar cycle variation of real ICME-associated CME latitudes during solar cycle 23 using
Song et al.’s method. The results show the following:
| • |
Although most of ICME-associated CMEs are distributed at low latitudes, there is a significant fraction of ICME-associated
CMEs occurring at high latitudes. 相似文献
15.
T. Appourchaux P. Liewer M. Watt D. Alexander V. Andretta F. Auchère P. D’Arrigo J. Ayon T. Corbard S. Fineschi W. Finsterle L. Floyd G. Garbe L. Gizon D. Hassler L. Harra A. Kosovichev J. Leibacher M. Leipold N. Murphy M. Maksimovic V. Martinez-Pillet B. S. A. Matthews R. Mewaldt D. Moses J. Newmark S. Régnier W. Schmutz D. Socker D. Spadaro M. Stuttard C. Trosseille R. Ulrich M. Velli A. Vourlidas C. R. Wimmer-Schweingruber T. Zurbuchen 《Experimental Astronomy》2009,23(3):1079-1117
The POLAR Investigation of the Sun (POLARIS) mission uses a combination of a gravity assist and solar sail propulsion to place
a spacecraft in a 0.48 AU circular orbit around the Sun with an inclination of 75° with respect to solar equator. This challenging
orbit is made possible by the challenging development of solar sail propulsion. This first extended view of the high-latitude
regions of the Sun will enable crucial observations not possible from the ecliptic viewpoint or from Solar Orbiter. While
Solar Orbiter would give the first glimpse of the high latitude magnetic field and flows to probe the solar dynamo, it does
not have sufficient viewing of the polar regions to achieve POLARIS’s primary objective: determining the relation between
the magnetism and dynamics of the Sun’s polar regions and the solar cycle.
16.
《Experimental Astronomy》2009,23(1):435-461
As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe
different characteristics of the instrument.
17.
Thierry Appourchaux Raymond Burston Yanbei Chen Michael Cruise Hansjörg Dittus Bernard Foulon Patrick Gill Laurent Gizon Hugh Klein Sergei Klioner Sergei Kopeikin Hans Krüger Claus Lämmerzahl Alberto Lobo Xinlian Luo Helen Margolis Wei-Tou Ni Antonio Pulido Patón Qiuhe Peng Achim Peters Ernst Rasel Albrecht Rüdiger Étienne Samain Hanns Selig Diana Shaul Timothy Sumner Stephan Theil Pierre Touboul Slava Turyshev Haitao Wang Li Wang Linqing Wen Andreas Wicht Ji Wu Xiaomin Zhang Cheng Zhao 《Experimental Astronomy》2009,23(2):491-527
ASTROD I is a planned interplanetary space mission with multiple goals. The primary aims are: to test general relativity with
an improvement in sensitivity of over three orders of magnitude, improving our understanding of gravity and aiding the development
of a new quantum gravity theory; to measure key solar system parameters with increased accuracy, advancing solar physics and
our knowledge of the solar system; and to measure the time rate of change of the gravitational constant with an order of magnitude
improvement and the anomalous Pioneer acceleration, thereby probing dark matter and dark energy gravitationally. It is an
international project, with major contributions from Europe and China and is envisaged as the first in a series of ASTROD
missions. ASTROD I will consist of one spacecraft carrying a telescope, four lasers, two event timers and a clock. Two-way,
two-wavelength laser pulse ranging will be used between the spacecraft in a solar orbit and deep space laser stations on Earth,
to achieve the ASTROD I goals. A second mission, ASTROD (ASTROD II) is envisaged as a three-spacecraft mission which would
test General Relativity to 1 ppb, enable detection of solar g-modes, measure the solar Lense–Thirring effect to 10 ppm, and
probe gravitational waves at frequencies below the LISA bandwidth. In the third phase (ASTROD III or Super-ASTROD), larger
orbits could be implemented to map the outer solar system and to probe primordial gravitational-waves at frequencies below
the ASTROD II bandwidth.
18.
M. Ollivier O. Absil F. Allard J.-P. Berger P. Bordé F. Cassaing B. Chazelas A. Chelli O. Chesneau V. Coudé du Foresto D. Defrère P. Duchon P. Gabor J. Gay E. Herwats S. Jacquinod P. Kern P. Kervella J.-M. Le Duigou A. Léger B. Lopez F. Malbet D. Mourard D. Pelat G. Perrin Y. Rabbia D. Rouan J.-M. Reiss G. Rousset F. Selsis P. Stee J. Surdej 《Experimental Astronomy》2009,23(1):403-434
PEGASE is a mission dedicated to the exploration of the environment (including habitable zone) of young and solar-type stars
(particularly those in the DARWIN catalogue) and the observation of low mass companions around nearby stars. It is a space
interferometer project composed of three free flying spacecraft, respectively featuring two 40 cm siderostats and a beam combiner
working in the visible and near infrared. It has been proposed to ESA as an answer to the first “Cosmic Vision” call for proposals,
as an M mission. The concept also enables full-scale demonstration of space nulling interferometry operation for DARWIN.
19.
The Space Infrared telescope for Cosmology and Astrophysics (SPICA) is planned to be the next space astronomy mission observing
in the infrared. The mission is planned to be launched in 2017 and will feature a 3.5 m telescope cooled to <5 K through the
use of mechanical coolers. These coolers will also cool the focal plane instruments thus avoiding the use of consumables and
giving the mission a long lifetime. SPICA’s large, cold aperture will provide a two order of magnitude sensitivity advantage
over current far infrared facilities (>30 microns wavelength). We describe the scientific advances that will be made possible
by this large increase in sensitivity and give details of the mission, spacecraft and focal plane conceptual design.
|