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1.
It is shown that inelastic proton collisions in extragalactic radio sources can account for their radio and -ray emissions. The proton Lorentz-factor p responsible for -ray emission is estimated to lie between 1.4 and 86. But for the radio emission (with e ~ 103-104) the estimated p values lie between 7 to 300. The estimates of total particle and magnetic energy for a typical radio source is in agreement with equipartition theory.  相似文献   

2.
Durney  Bernard R. 《Solar physics》1998,180(1-2):1-17
The power in the different modes of an expansion of the solar radial magnetic field at the surface in terms of Legendre polynomials,P , is calculated with the help of a solar dynamo model studied earlier. The model is of the Babcock–Leighton type, i.e., the surface eruptions of the toroidal magnetic field – through the tilt angle, , formed by the magnetic axis of a bipolar magnetic region with the east-west line – are the sources for the poloidal field. In this paper it is assumed that the tilt angle is subject to fluctuations of the form, = ()+ <> where <> is the average value and () is a random normal fluctuation with standard deviation which is taken from Howard's observations of the distribution of tilt angles. For numerical considerations, negative values of were not allowed. If this occurred, was recalculated. The numerical integrations were started with a toroidal magnetic field antisymmetric across the equator, large enough to generate eruptions, and a negligible poloidal field. The fluctuations in the tilt angle destroy the antisymmetry as time increases. The power of the antisymmetric modes across the equator (i.e., odd values of ) is concentrated in frequencies, p, corresponding to the cycle period. The maximum power lies in the =3 mode with considerable power in the =5 mode, in broad agreement with Stenflo's results who finds a maximum power at =5. For the symmetric modes, there is considerable power in frequencies larger than p, again in broad agreement with Stenflo's power spectrum.  相似文献   

3.
In our preceding paper {see [L. Sh. Grigorian and S. Gottlöber, Astrofizika (in press)]} we investigated a self-gravitating system consisting of a scalar field and a linear tensor field ik= ki with minimal coupling and with allowance for the action of vacuum polarization effects. In the present paper we investigate the case of a nonlinear tensor field ik. The action S () of the field ik is determined by the difference Rik — ik, where Rik is the space-time Ricci tensor and Rik is the analogous quantity constructed using the metric ik=gik+ik induced by ik ( is a free parameter). Here S () coincides with the previously known expression for the action of a linear field ik. Equations of motion are derived for ik in curved space-time. The energy-momentum metric tensor, determining the contribution of ik to the gravitational field equations, is calculated.Translated from Astrofizika, Vol. 39, No. 1, pp. 135–144, January-March, 1996.  相似文献   

4.
Lockwood  J. A.  Debrunner  H.  Ryan  J. M. 《Solar physics》1997,173(1):151-176
We have examined six solar neutron events measured by satellite instruments and/or neutron monitors (NM) to understand the relationship between the intensity–time profiles of the -ray lines, the pion-related -rays, and the neutron production. In all six events the solar neutron production was clearly time-extended. We find that neutron emission as detected by NMs most closely follows the emission of pion-related -rays, whereas lower energy neutron production may follow that of nuclear -ray line emissions. Although this distinction is not unexpected, it is safe to say that the 2.223 MeV -ray line from neutron capture on hydrogen is a poor measure of the neutron production at energies >200 MeV. During the three events on 1982, June 3, 1990, May 24 and 1991, June 4 solar neutrons with energies greater than 200 MeV were recorded by NMs. The NM increases on 1982, June 3 and 1990, May 24 can be modeled using the time profile of the pion-related -rays. For the 1991, June 4 event the NM signal was small but lasted for 60 min and the high-energy -ray data available to us are insufficient to conclude unambiguously that the high-energy neutron production followed the pion-related -rays. In the other three events on 1991, June 9, 11, and 15 solar neutrons with energies 10–100 MeV were observed by the COMPTEL -ray instrument on the Compton Gamma Ray Observatory. The duration of the low-energy neutron production on 1991, June 9 corresponded clearly to the high-energy and not to the low-energy -ray emission.  相似文献   

5.
We determine the momentum distribution of the relativistic particles near the Crab pulsar from the observed X- and -ray spectra (103109 eV), provided that the curvature radiation is responsible for it. The power law spectrum for the relativistic electrons,f() –5, reproduces a close fit to the observed high-energy photon spectrum. The theoretically determined upper limit to the momentum (due to radiation damping), M 8×106, corresponds to the upper cut-off energy of the -ray spectrum, 109 eV. The lower limit to the momentum, m 1.8×105, is chosen such that flattening of the X-ray spectrum below 10 keV is simulated. The number density of these electrons is found to be much higher than the Goldreich-Julian density. We also discuss pulse shape and polarization of high-energy photons. The extremely high density of particles and the steep momentum spectrum are difficult to understand. This may imply that another, more efficient, mechanism is in operation.  相似文献   

6.
We examine a simple statistical consequence of relativistic beaming model using the core-to-lobe flux density ratio (R) and projected linear size (D) as orientation indicators. It is shown that the observed R-D intercept for the 3CRR source sample provides values of the bulk Lorentz factor () which are consistent with the beaming scenario. The result also shows that if the lobe-dominated quasars are to be unified with the core-dominated quasars, they should be oriented at a median angle, _med 40° with respect to the line of sight, but if with powerful radio galaxies, then _med 24°. Application of this result to the quasar-galaxy unification scheme using the observed angular size-redshift relation shows that the scheme is consistent with the observed data.  相似文献   

7.
The cosmic -ray spectrum below 1 GeV arising from cosmic ray p-p interactions is calculated. Its characteristics are determined by the properties of secondary neutral pion production occurring at accelerator energies. A model is chosen for numerical calculations in which the two dominant modes of neutral pion production at accelerator energies are the production of the (1.238) isobar and one fireball. The effect of -p and p- interactions on the cosmic -ray spectrum is also calculated. The final results are given in terms of both differential and integral -ray energy spectra.  相似文献   

8.
The new class of -ray spectra from impulsive flares without nuclear -ray lines is compared with bremsstrahlung spectra of energetic electrons undergoing stochastic acceleration, Coulomb and synchrotron losses. The remarkable agreement of both the produced -spectra from the precipitated electrons and the electron spectra measured in the interplanetary space leads to the conclusion that seed population and acceleration process are identical for both classes of electrons. A new estimate of the electron bremsstrahlung contribution in -spectra of impulsive solar flares seems to be necessary.  相似文献   

9.
We determine empirical damping constants for 73 selected Fe i lines following the method of Gurtovenko and Kondrashova (1980), employing high-quality observations and the accurate list of Fe i oscillator strengths by Gurtovenko and Kostik (1980).The results show: (i) No increase of the enhancement factor to van der Waals broadening with excitation potential, as predicted by Edmunds (1975), and with the frequency of the transition (Figure 1); (ii) a substantial part of the commonly-used enhancement factor for weaker lines is not due to collisional damping (Figure 2), but to a misrepresentation of the inhomogeneous structure of the deep photosphere. This false damping effect is not seen in the stronger lines which yield an average damping constant : 1.36 1.5 6.  相似文献   

10.
The method of obtaining the estimates of the maximalt-interval ( –, +) on which the solution of theN-body problem exists and which is such that some fixed mutual distance (e. g. 12) exceeds some fixed non-negative lower bound, for allt contained in ( –, +), is considered. For given masses and initial data, the increasing sequences of the numbers k , each of which provides the estimate + > k , are constructed. It appears that if + = +, then .  相似文献   

11.
It is shown that bremsstrahlung from electrons with Lorentz factor 1 is suppressed for >p in a plasma with plasma frequency p compared with emission in vacuo. For p the ratio of the power emitted per unit frequency in the plasma to that in vacuo varies as 2.This suppression effect is analogous to the suppression of synchrotron radiation in a plasma (Razin-Tsytovich effect). It is argued that such suppression is a characteristic property of emission by relativistic particles in a plasma.  相似文献   

12.
Previous studies have shown that the largest -ray detector to date, EGRET, does not have useful polarization sensitivity. We have explored here some improved approaches to analyzing -ray pair production events, leading to important gains in sensitivity to polarization. The performance of the next generation -ray instrument GLAST is investigated using a detailed Monte Carlo simulation of the complete detector.  相似文献   

13.
Two hyades giant stars, and Tau, have been studied from an analysis of strong line profiles. We get for Tau,T e =4750K and logg=2.7, and for Tau,T e =4700K and logg=2.8. Hydrogen-to-metal ratio for the two stars is nearly the same as that of solar value.  相似文献   

14.
Three active galaxies, generally classified as Seyferts, have been discovered recently to be powerful, low energy -ray sources. The similarity between their spectral characteristics and those of the cosmic background at -ray energies suggests that these objects could make a significant contribution to this diffuse flux. This contribution has been assessed using two different number densities of -ray-emitting Seyfert galaxies based on optical and X-ray data. The comparison of the estimated and measured diffuse -ray background intensities is used to gain a deeper understanding of the metabolism of Seyfert galaxies.  相似文献   

15.
M. Velli  A. W. Hood 《Solar physics》1986,106(2):353-364
The stability of coronal arcades to localized resistive interchange modes in the ballooning ordering, including photospheric line tying, is investigated. It is found that the anchoring of magnetic footpoints in the photosphere is not sufficient to stabilise ballooning modes, once resistivity is taken into account. All configurations with a pressure profile decreasing from the arcade axis at some point are unstable, a purely growing mode being excited. The dependence of the growth rate on the parameter Rm –1 k 2 , where is the resistivity and k the wavenumber in a direction perpendicular to the equilibrium field, can be described by a power law with varying index: for small values of k 2 and an ideally stable field one finds Rm –1. As k 2 is increased or marginal stability is approached one finds Rm–1/3. T implications of these localised instabilities to the temporal evolution and overall energy balance of arcade structures in the solar corona is discussed.  相似文献   

16.
We have mapped two solar active regions using the VLA at three closely spaced frequencies (4496, 4716, and 4996 MHz) in an attempt to determine the origin of the steep spectra (index –5 to –8) sometimes observed with large single telescopes. One of the regions observed indeed shows an anomalously large slope ( –6) compared to the usual ( –2 to –2.5). The other region shows a similar slope ( –5) but with a larger range of statistical error. Two possible explanations for such steep edges in solar spectra are (1) transmission effects of neutral current sheets, and (2) the appearance of cyclotron lines. The internal evidence of the microwave maps and simultaneous optical observations favor an explanation in terms of cyclotron lines.On leave from Indian Institute of Astrophysics, Bangalore, India.  相似文献   

17.
The observations of the BATSE instrument on the Compton Gamma-Ray Observatory show that the spatial distribution of -ray burst sources is isotropic but radially non-uniform. As is well known, the spectral features, the time histories and the X-ray tails present in some -ray bursts suggest that they may arise from galactic neutron stars. But, low velocity neutron stars born in the Galactic disk would concentrate toward the galactic plane and center, and could not fit the BATSE results. However, the high velocity neutron stars with velocity 1000 km s–1 may escape from the Galactic gravitational field and form a nearly isotropic distribution. Here we calculate the three statistical values of V/V max, sin2 b and cos as functions of the intensitiesC max/C min and find that they could be fitted by the distribution of high velocity neutron stars under the assumption that the high velocity neutron stars should turn on as -ray burst sources only after some time (perhaps after they have ceased to be radio pulsars). Our calculation shows that the statistical value of cos is more sensitive than sin2 b to the angular distribution of high velocity neutron stars, i.e. the deviation of cos from 0 is more readily detected than the deviation of sin2 b from 1/3, so we expect that with the increasing sensitivity of instrument and the more exact value of cos , it is possible to determine whether this high velocity neutron star model is correct. Some results are discussed in the text.  相似文献   

18.
The observed energy spectra in synchrotron sources are power laws,N (E)=KE –, with the distribution in peaked around 2.5. These are consistent with initially injected spectra with between 1 and 2, subsequently steepened by synchrotron losses. Contrary to the results of Kardashev (1962), it is shown that statistical acceleration when coupled with synchrotron losses lead naturally to the formation of flat stationary spectra with 1. These stationary spectra have bends near the energy at which synchrotron losses balance the energy gains by acceleration. Above this bend the spectrum tends to =2. The time evolution of an initial spectrum towards the stationary spectrum is investigated. It is suggested that the initially flat spectra with 1 to 1.5 observed in some variable sources result from an incomplete approach to the stationary spectrum, and that in sources with constant acceleration spectra with 2 are to be expected.  相似文献   

19.
The electrical conductivity of the lunar interior has been determined from magnetic field step transients measured on the lunar dark side. The simplest model which best fits the data is a spherically symmetric three layer model having a nonconducting outer crust of radial thickness 0.03R moon; an intermediate layer of thicknessR0.37R moon, with electrical conductivity 1 3.5 × 10–4 mhos/m; and an inner core of radiusR 2 0.6R m with conductivity 2 10–2 mhos/m. Temperatures calculated from these conductivities in the three regions for an example of an olivine Moon are as follows: crust, < 440 K; intermediate layer, 890 K; and core, 1240 K. The whole-moon relative permeability has been calculated from the measurements to be/ 0 = 1.03 ± 0.13. Remanent magnetic fields at the landing sites are 38 ± 3 at Apollo 12, 43 ± 6 and 103 ± 5 at two Apollo 14 sites separated by 1.1 km, and 6 ± 4 at the Apollo 15 site. Measurements show that the 38 remanent field at the Apollo 12 site is compressed to 54 by a solar wind pressure increase of 7 × 10–8 dynes/cm2.National Research Council Postdoctoral Associate.  相似文献   

20.
A report on preliminary results obtained from the analysis of the first 700 orbits of data obtained in the University of Rochester particle telescope, carried in the wheel section of OSO-III, is presented. The telescope is sensitive to high-energy -rays (threshold 50 MeV) and the nuclear component of the cosmic radiation. An upper limit of 3.2 × 10–4 /cm2secster. is set on the intensity of the diffuse primary -radiation, on the assumption it arises from the decay of ° mesons produced in nuclear interactions. An upper limit to the flux from the sun, on the same assumptions, is set at 5.5 × 10–5 /cm2 sec. The analysis of the charged particle data yields the integral rigidity spectra of proton and helium nuclei from 3 to 15 GV; the results indicate that the He spectrum is slightly steeper than the proton spectrum and that the ratio P/He increases slowly from a value of approximately 6 at 3 GV to 8 at 15 GV.NASA Predoctoral Trainee.  相似文献   

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