共查询到20条相似文献，搜索用时 406 毫秒
1.
2.
S. T. Suess 《Solar physics》1971,18(1):172-175
Some recent observations of the Sun suggest a class of wave-like motions moving both eastward and westward at a uniform velocity with respect to the mean solar angular velocity. It is suggested that these may be hydromagnetic planetary waves. An estimate of the mean toroidal magnetic field is made, based on a theoretical treatment of such waves already in the literature, and a slight correction to the mean rate of rotation of the Sun is inferred. 相似文献
3.
Love numbers of second order of Venus are calculated with resolving fundamental differential equations of elastic body according
to the parameters of the density and the elasticity of material by means of the PVM94-01 Venus model. Meanwhile, the elastic
energy of deformation of second order due to the tidal perturbation of the Sun and that due to rotational centrifugal potential
are also calculated. The values of Love number provide a basis for model of internal structure of Venus. The numerical calculation
of the elastic energy of deformation gives a magnitude evaluation of the perturbation terms to the Hamiltonian expressions
in the study of dynamics of the elastic Venus.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
The source of coronal magnetic energy and helicity lies below the surface of the Sun, probably in the convective zone dynamo. Measurements of magnetic and velocity fields can capture the fluxes of both magnetic energy and helicity crossing the photosphere. We point out the ambiguities which can occur when observations are used to compute these fluxes. In particular, we show that these fluxes should be computed only from the horizontal motions deduced by tracking the photospheric cut of magnetic flux tubes. These horizontal motions include the effect of both the emergence and the shearing motions whatever the magnetic configuration complexity is. We finally analyze the observational difficulties involved in deriving such fluxes, in particular the limitations of the correlation tracking methods. 相似文献
5.
Wu-Ming Yang Shao-Lan Bi 《中国天文和天体物理学报》2008,8(6)
We investigate the rotation profile of solar-like stars with magnetic fields. A diffu-sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 σ level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 M⊙, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass. 相似文献
6.
Ch. V. Sastry 《Solar physics》1994,150(1-2):285-294
We have mapped the continuum emission from the undisturbed Sun at a wavelength of 8.7 m during 1981–1985 using the large decameter-wave
radiotelescope at Gauribidanur, India with a resolution of 26 #x00D7; 38 arc min. During the period August 6–30, 1983, the
Sun was exceptionally quiet at meter and decameter wavelengths, and we were able to make maps on several consecutive days.
On these days the position of the centroid of the radio Sun agreed quite closely with the center of the optical Sun indicating
that there is very little or no contribution from active regions. But the observed peak brightness temperature varied from
100 000 to 700 000 K. The half-power widths of the brightness distribution were in the range of 3 to 4R
⊙. The variations of the brightness temperature and the half-power widths are not correlate. It is therefore suggested that
the variations of the brightness temperature are not caused by uniform density variations or due to scattering by an irregular
corona. 相似文献
7.
GRS 1915+105是银河系内的低质量黑洞X射线双星,其能谱和黑洞自旋已经得到了广泛的研究.自2018年6月开始,其X射线流量下降到了低流量水平,其间偶尔会产生多波段的耀发.利用Insight-HXMT(Insight-Hard X-ray Modulation Telescope,简称为慧眼)卫星在2020年8月30日到2020年10月13日之间对GRS1915+105的观测数据,研究了其能谱特性,发现在此次爆发过程中, X射线能谱可以用一个康普顿化的多温黑体谱很好地拟合.整个爆发的硬度强度图(Hardness-Intensity Diagram, HID)一直处于软态.采用GRS1915+105的最新动力学参数M=12.4-1.8+2.0M⊙, i=60°±5°, D=8.6-1.6+2.0kpc (M、M⊙、i和D分别表示黑洞质量、太阳质量、盘倾角和距离),得到其无量纲黑洞自旋a*的一个下限a*> 0.9990,确认了GRS 1915+105是一个具有极端自旋的黑洞.考虑本地吸收体的... 相似文献
8.
The anisotropy of the particle distribution and its variation with time at 1 AU early in a solar cosmic ray event can provide information on the pitch-angle scattering of the particles in the interplanetary medium. The proton event of 20 April 1971 is described in which the anisotropy of the 7.6–55 MeV energy channel remained large (? 100%) and field-aligned well into the decay phase of the event. A Monte Carlo technique, which gives the pitch-angle distribution, is employed to investigate two models put forward to explain this sustained anisotropy. It is shown that the observed event is consistent with one model in which the injection of particles at the Sun decayed with ane-folding time of 7 hr. In this model the parallel propagation is determined by small-angle scattering in a diverging field equivalent to a uniform diffusion coefficient of 2.1 × 1022 cm2 s?1 (the corresponding classical mean free path is 0.90 AU). A model with impulsive injection and in whichκ(r) increases strongly with distance from the Sun cannot satisfactorily explain the observations. 相似文献
9.
We calculate the total energy dissipation rate of a dust-acoustic wave on a uniform background medium, in which the dust is not a dominant charge carrier, as a function of the dust-acoustic wavelength and dust parameters and give results for the deposition rates in each of the dust, ion and electron fluids. 相似文献
10.
We present data and modelling for the quiet Sun that strongly suggest a ubiquitous small-scale atmospheric heating mechanism
that is driven solely by converging supergranular flows. A possible energy source for such events is the power transfer to
the plasma via the work done on the magnetic field by photospheric convective flows, which exert drag on the footpoints of
magnetic structures. We present evidence of small-scale energy release events driven directly by the hydrodynamic forces that
act on the magnetic elements in the photosphere, as a result of supergranular-scale flows. We show strong spatial and temporal
correlation between quiet-Sun soft X-ray emission (from Yohkoh SXT) and SOHO MDI-derived flux removal events driven by deduced photospheric flows. We also present a simple model of heating
generated by flux submergence, based on particle acceleration by converging magnetic mirrors. In the near future, high resolution
soft X-ray images from XRT on the Hinode satellite will allow definitive, quantitative verification of our results.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
11.
We present results on the energy balance of the Deep Impact experiment based on analysis of 180 infrared spectra of the ejecta obtained by the Deep Impact spacecraft. We derive an output energy of 16.5 (+9.1/−4.1) GJ. With an input energy of 19.7 GJ, the error bars are large enough so that there may or may not be a balance between the kinetic energy of the impact and that of outflowing materials. Although possible, no other source of energy other than the impactor or the Sun is needed to explain the observations. Most of the energy (85%) goes into the hot plume in the first few seconds, which only represents a very small fraction (<0.01%) of the total ejected mass. The hot plume contains 190 (+263/−71) kg of H2O, 1.6 ± 0.5 kg of CO2, 8.2 (+11.3/3.1) kg of CO (assuming a CO/H2O ratio of 4.3%), 27.9 (+25.0/−8.9) kg of organic material and 255 ± 128 kg of dust, while the ejecta contains ∼107 kg of materials. About 12% of the energy goes into the ejecta (mostly water) and 3% to destroy the impactor. Volatiles species other than H2O (CO2, CO or organic molecules) contribute to <7% of the energy balance. In terms of physical processes, 68% of the energy is used to accelerate grains (kinetic energy), 16% to heat them, 6% to sublimate or melt them and 10% (upper limit) to break and compress dust and/or water ice aggregates into small micron size particles. For the hot plume, we derive a dust/H2O ratio of 1.3 (+1.9/−1.0), a CO2/H2O ratio of 0.008 (+0.009/−0.006), an organics/H2O ratio of 0.15 (+0.29/−0.11) and an organics/dust ratio of 0.11 (+0.30/−0.07). This composition refers to the impact site and is different from that of the bulk nucleus, consistent with the idea of layers of different composition in the nucleus sub-surface. Our results emphasize the importance of laboratory impact experiments to understand the physical processes involved at such a large scale. 相似文献
12.
A re-analysis of the brightness distribution of the quiet Sun at 1.2 mm wavelength is made. It is concluded that there is no evidence for uniform or limb-brightened distribution at this wave-length. 相似文献
13.
We discuss a mechanism of energy production associated with the acoustic and MHD shocks produced by colliding and reconnecting
flux tubes and present the observational results showing a connection between the dynamic changes in the photosphere and the
high velocity and heating events in the transition region. We suggest that these processes may provide a constant energy supply
for the origin of the fast wind and help to advance studies of coronal dynamics.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
The Electron Energy Spectrum from Large Solar Flares 总被引：2，自引：0，他引：2
G. M. Simnett 《Solar physics》2006,237(2):383-395
We report on the differential electron spectrum for intense transient events seen at one AU by the EPAM instrument on the
Advanced Composition Explorer (ACE) spacecraft. Over an observing period from September 1997 to September 2005, there were 45 major events that could be
reliably identified with a source flare on the Sun. In the ∼40 – 300 keV energy range, the electron spectral index was between
one and three for all but two of the events. Twenty-five of the events were associated with Geostationary Operational Environmental
Satellites (GOES) X-ray class X flares. We compare this result with the spectral index measured from electron pulse events,
lasting approx. one hour or less, where the spectral index is typically much softer than three. This suggests that the measured
spectral index of near-relativistic electrons at one AU may be a reliable indicator of the source. We also examine the likelihood
that fast coronal mass ejections (CMEs) are responsible in themselves for accelerating near-relativistic electrons and conclude
that they do not. 相似文献
15.
Kantowski-Sachs cosmological model in the presence of magnetized anisotropic dark energy is investigated. The energy-momentum
tensor consists of anisotropic fluid with anisotropic EoS p=ωρ and a uniform magnetic field of energy density ρ
B
. We obtain exact solutions to the field equations using the condition that expansion is proportional to the shear scalar.
The physical behavior of the model is discussed with and without magnetic field. We conclude that universe model as well as
anisotropic fluid does not approach isotropy through the evolution of the universe. 相似文献
16.
The solution of the classical problem of two-dimensional magnetohydrodynamic (MHD) interaction between two shocks (the angle between the interacting shocks and the slope of the magnetic field are arbitrary) obtained by Pushkar' (1995) is applied to the problem of interaction between interplanetary shocks and the solar wind termination shock (TS). The self-consistent kinetic-gasdynamic model of solar wind interaction with the supersonic flow of a three-component (electrons, protons, and hydrogen atoms) interstellar medium developed for the axisymmetric, steady-state case by Baranov and Malama (1993) is used as the stationary background against which the physical phenomenon under consideration takes place. The main physical process in this model is the resonant charge exchange between protons and hydrogen atoms. This paper is a natural continuation of our previous papers (Baranov et al. 1996a, 1996b). However, whereas attention in these papers was focused on the TS interaction with an interplanetary forward shock moving away from the Sun, here we consider the TS interaction with an interplanetary reverse shock (RS) moving toward the Sun with a velocity lower than the solar-wind velocity. We show that the TS-RS interaction can give rise to a new TS' that moves toward the Sun, i.e., toward Voyager 1 and Voyager 2. This phenomenon may be responsible for the unexpected suggestion made by some of the scientists that Voyager 1 already crossed TS in the past year. This conclusion was drawn from the interpretation of the intensity, energy spectra, and angular distributions of ions in the energy range from 10 keV to 40 MeV measured from this spacecraft. Our results show that Voyager 1 could cross TS' rather than TS. 相似文献
17.
Richard A. Harrison 《Solar physics》1997,175(2):467-485
A search for microflare activity in the extreme ultraviolet (EUV) quiet Sun using the Coronal Diagnostic Spectrometer (CDS)
aboard the Solar and Heliospheric Observatory (SOHO) spacecraft has not resulted in the identification of microflare activity,
but has resulted in the identification of a hitherto unknown phenomenon: enhancements of a factor of 2–3 in the flux of transition
region lines at network junctions. A total of some 6 hours of observation of 5 different target areas showed this ‘blinker’
activity at each area, with durations ranging from 1 to 30 min and averaging 13 min, and thermal energy content of order 10-6 that of a ‘standard’ flare. Assuming that the observations are of typical quiet Sun, and projecting these data to predict
a distribution of these events over the entire Sun, the total thermal energy content of these ‘blinkers’ is insignificant
when compared to the energy required to heat the corona. The nature of these events and their significance are discussed in
this paper. 相似文献
18.
We study Bianchi type I cosmological model in the presence of magnetized anisotropic dark energy. The energy-momentum tensor consists of anisotropic fluid with anisotropic EoS p=ω ρ and a uniform magnetic field of energy density ρ B . We obtain exact solutions to the field equations using the condition that expansion is proportional to the shear scalar. The physical behavior of the model is discussed with and without magnetic field. We conclude that universe model as well as anisotropic fluid do not approach isotropy through the evolution of the universe. 相似文献
19.
M. Joyce B. Marcos F. Sylos Labini 《Monthly notices of the Royal Astronomical Society》2009,397(2):775-792
When an open system of classical point particles interacting by Newtonian gravity collapses and relaxes violently, an arbitrary amount of energy may, in principle, be carried away by particles which escape to infinity. We investigate here, using numerical simulations, how this released energy and other related quantities (notably the binding energy and size of the virialized structure) depend on the initial conditions, for the one-parameter family of starting configurations given by randomly distributing N cold particles in a spherical volume. Previous studies have established that the minimal size reached by the system scales approximately as N 1/3 , a behaviour which follows trivially when the growth of perturbations (which regularize the singularity of the cold collapse in the N →∞ limit) is assumed to be unaffected by the boundaries. Our study shows that the energy ejected grows approximately in proportion to N 1/3 , while the fraction of the initial mass ejected grows only very slowly with N , approximately logarithmically, in the range of N simulated. We examine in detail the mechanism of this mass and energy ejection, showing explicitly that it arises from the interplay of the growth of perturbations with the finite size of the system. A net lag of particles compared to their uniform spherical collapse trajectories develops first at the boundaries and then propagates into the volume during the collapse. Particles in the outer shells are then ejected as they scatter through the time-dependent potential of an already re-expanding central core. Using modified initial configurations, we explore the importance of fluctuations at different scales and discreteness (i.e. non-Vlasov) effects in the dynamics. 相似文献
20.
The differential flux and energy spectra of solar cosmic ray heavy ions of He, C, O, Ne, Mg, Si, and Fe were determined in the energy interval E = 3–30 MeV amu-1 for two large solar events of January 24, 1971 and September 1, 1971 in rocket flights made from Ft. Churchill. From these data the relative abundances and the abundance enhancement factors, ξ, relative to photospheric abundances were obtained for these elements. Similar results were obtained for a third event on August 4, 1972 from the available published data. Characteristic features of ξ vs nuclear charge dependences were deduced for five energy intervals. The energy dependence of ξ for He shows a moderate change by a factor of about 3, whereas for Fe, ξ shows a very dramatic decrease by a factor of 10–20 with increasing energy. It is inferred that these abundance enhancements of solar cosmic ray heavy ions at low energies seem to be related to their ionization states (Z *) and hence studies of Z * can give information on the important parameters such as temperature and density in the accelerating region in the Sun. 相似文献