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1.
Gary  G. Allen 《Solar physics》2001,203(1):71-86
In this paper, we present a model of the plasma beta above an active region and discuss its consequences in terms of coronal magnetic field modeling. The -plasma model is representative and derived from a collection of sources. The resulting variation with height in the solar atmosphere is used to emphasize that the assumption that the magnetic pressure dominates over the plasma pressure must be carefully employed when extrapolating the magnetic field. This paper points out (1) that the paradigm that the coronal magnetic field can be constructed from a force-free magnetic field must be used in the correct context, since the force-free region is sandwiched between two regions which have >1, (2) that the chromospheric Mgii–Civ magnetic measurements occur near the -minimum, and (3) that, moving from the photosphere upwards, can return to 1 at relatively low coronal heights, e.g., R1.2 R s.  相似文献   

2.
This paper presents the results of the study on the periodicity in filament activity. The spectral analysis of the number of filaments shows a basic period at 141 (10.5 yr), at 138 (10.3 yr), and at 144 (10.7 yr) Carrington rotation in the northern and southern hemisphere, respectively.The time series concerning the index of filament activity shows also a typical period at 135 Carrington rotation (10.1 yr) at 144 Carrington rotation (10.7 yr) and at 133 Carrington rotation (9.9 yr), respectively, in the northern and southern hemisphere.The power spectrum analysis of the time series of the filamentary activity in the short-term also yields less pronounced but still noticeable peaks which are statistically significant.  相似文献   

3.
Multiband observations of the AM Herculis-type binary CW1103+254 show significant circular polarization (13%) in the J band. Recently, a model with high temperature (kT20 keV) and small dimensionless plasma parameter (104) was suggested for the emitting region. However, it gives negligible polarization in the J band. In this paper, a method, in which the J band polarization and the peak frequency of the spectrum are taken into account, is used to determine T and . For the viewing angle =80° and the magnetic field B=30MG, we find that kT=5.0 keV and =106. The temperature of the emitting region is close to the value (kT=8.7 keV) derived for the region emitting cyclotron lines in VV Puppis. If these radiations arise from the post-shock regions, then these temperatures are significantly lower than those predicted by standard accretion models or the shock structure is inhomogenous and more complex than previously assumed.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.  相似文献   

4.
A 3 mm low noise beam-lead Schottky diode mixer has been developed. At cryogenic temperatures the conversion loss is 6.3 dB, and the DSB mixer noise temperature is 75 K, respectively. The mixer was installed into the cooled receiver for radioastronomical observations at the Metsähovi 13.7-m radio telescope. Total DSB noise temperature of the cooled receiver with an ultra low noise HEMT IF amplifier was 110 K at 103 GHz. The tuning range of the mixer mount was from 70 GHz to 115 GHz.  相似文献   

5.
Spherically symmetric, steady-state, optically thick accretion onto a nonrotating black hole with the mass of is studied. The gas accreting onto the black hole is assumed to be a fully ionized hydrogen plasma withn 0=108 cm–3 andT 0=104 K far from the black hole, and a new approximate expression for the Eddington factor is introduced. The luminosity is estimated to beL=1.875×1033 erg s–1, which primarily arises from the optical surface (1) ofT104 K. The accretion flow is characterized by 1 and (v/c)10. In the optically thin region, the flow remains isothermal, and the increase of temperature occurs at 1. The radiative equilibrium is strictly realized at (v/c)10.  相似文献   

6.
A coronal bright point is resolved into a pattern of emission which, at any given time, consists of 2 or 3 miniature loops (each 2500 km in diameter and 12 000 km long). During the half-day lifetime of the bright point individual loops evolved on a time scale 6 min. A small ctive region seemed to evolve in this way, but the occasional blurring together of several loops made it difficult to follow individual changes.  相似文献   

7.
Time sequences of simultaneous spectra of limb spicules, obtained using the Sacramento Peak Observatory's tower telescope and echelle spectrograph are analyzed. Intensity determinations of H and K, H, 8498 and 8542 of calcium are tabulated for three observing heights. Electron densities averaged over the entire visible lifetimes of spicules are -6 × 1010 cm–3 at observing heights of 6000km, while maximum and minimum values were -1.1 × 1011 cm–3 at 6000km and - 2 × 1010 cm–3 at 10000km. Electron temperatures range between 12 000 K and 16 000 K. Profile halfwidths indicate turbulent velocities of 12 to 22 km s–1, and spectral tilts are interpreted as caused by differential velocity fields of -3 km s–1 per 1000 km. No large scale spicule expansions or contractions are observed, although possible expulsions or accretions of material are observed. Spicules may be wider in the calcium K and H lines than in H.Now at School of Science and Engineering, The University of Alabama in Huntsville, Huntsville, Alabama.  相似文献   

8.
The long-time series of daily means of cosmic-ray intensity observed by four neutron monitors at different cutoff rigidities (Calgary, Climax, Lomnický tít and Huancayo/Haleakala) were analyzed by means of the wavelet transform method in the period range 60 to 1000 days. The contributions of the time evolution of three quasi-periodic cosmic-ray signals (150 d, 1.3 yr and 1.7 yr) to the global one are obtained. While the 1.7-yr quasi-periodicity, the most remarkable one in the studied interval, strongly contributes to the cosmic ray intensity profile of solar cycle 21 (particularly in 1982), the 1.3-yr one, which is better correlated with the same periodicity of the interplanetary magnetic field strength, is present as a characteristic feature for the decreasing phases of the cycles 20 and 22. Transitions between these quasi-periodicities are seen in the wavelet power spectra plots. Obtained results support the claimed difference in the solar activity evolution during odd and even solar activity cycles.  相似文献   

9.
The inflationary unvierse model predicts the density parameter 0 to be 1.0 with the cosmological constant 0 usually taken to be zero, whereas observational estimates give 00.2 and 010-57 cm–2. It was found, however, that the observed variation of angular diameter with redshift for extragalactic radio sources could be interpreted in terms of a low density universe with linear size evolution of the sources for either an inflationary model with 0 or an open model with =0.  相似文献   

10.
. - . . , . - . - , , , -. ., , .
The structure of rotating magnetic polytropes is considered in Roche approximation. Investigation of the influence of poloidal as well as toroidal magnetic fields on the conditions of the beginning of matter outflow due to rotational instability is carried out. The influence of the turbulent convection and twisting of magnetic force-lines on the time of smoothing of differential rotation is considered. The estimate of the magneto-turbulence energy generated by differential rotation is presented. Both maximum possible energy output and duration of the quasi-statical evolution phase up to the appearance of hydrodynamic instability due to the effects of general relativity are calculated for supermassive magnetic polytropes of index three with uniform or differential rotation. The radius-mass relation is obtained for supermassive differentially-rotating magnetic polytropes referring to the longest part of the quasi-statistical evolution stage; some consequences are pointed out, including the period-luminosity relation.The evolution of the considered models of supermassive rotating magnetic polytropes with different character of rotation and different geometry of a magnetic field is discussed.The results obtained are summarized in the last section.

English translation will appear in the next issue ofAstrophys. Space Sci.

Receipt delayed by postal strike in Great Britain  相似文献   

11.
From theH filtergram observations obtained at Ganyu station, identification and statistic works made for Ellerman bombs, it is found that they often occur in the superpenumbra area of a mature sunspot. We suggest a plasmoid model to account for the basic properties of a typical bomb: lifetime 11 min, diameter 5 × 107 cm, accompanying jet velocity 40 km/s, total energy 1027 erg,Te 104 K. First, a numerical simulation is made to prove that plasmoids can be lifted from the solar convective zone by magnetic buoyancy. Between the plasmoid and its surroundings a strong current sheet builds up in which a peculiar MHD (with plasma ponderamotive force) - resistive instability takes place. After the magnetic reconnection has begun, a local explosive instability ensues whose growth rate is so high that it allows the exhaustion of the high temperature particles from the sheet in a short period. In this way, the temperature of a bomb may be kept unchanged or only rise slightly.  相似文献   

12.
An analysis of the longitudinal distribution of gamma rays from SAS-II data has been carried out using the available information on the gas distribution in the Galaxy. The overall distribution of cosmic rays in the galactic plane can be represented by an exponential function in galactocentric distance with a scale length of 8 kpc upto the solar circle and 10 kpc beyond. There is no evidence for a large gradient of the cosmic ray intensity in the outer parts of the Galaxy. The local emissivities of gamma rays in the energy regionsE >100 MeV and 35 MeV<E <100 MeV are (1.73±0.27)×10–25 photon/(cm3 s nH) and (2.40±0.41)×10–25 photon/(cm3 s nH) respectively. The contribution of °-decay gamma rays is 80% forE >100 MeV and 20% at lower energies. The electron spectrum required by this analysis has a power law spectral index of about –2.7 below a few hundred MeV. The observed gas distribution towards the galactic centre would predict a gamma-ray flux larger than observed. It is suggested that the molecular gas in the central region may be in the form of dense coudlets, in which low evergy cosmic rays do not penetrate; in this case the centre should be seen as a strong source only at high energies. An analysis of the radio sky survey map of the Galaxy at 408 MHz shows thatB varies with a scale-length of 40 kpc; no significance can be attached to the apparent deviation from the equipartition of energy densities between cosmic rays and magnetic field. The derived local emissivity is (1.46±0.28)×10–40 W/((m3 Hz), which corresponds toB 5 G. The surface brightness of radio and gamma-ray emissions in the Galaxy decreases from the centre with scale-lengths 6 kpc and 7 kpc respectively. No positive correlation can be noticed with either co-rotation radius or pattern speed, when compared with external spiral galaxies.  相似文献   

13.
The reduction of observations of the O i 7773 triplet obtained at high spatial resolution (0.5) at two disk positions is described. Two sets of triplet profile data are presented at each disk position. One set represents data taken from 0.5 regions centered on the brightest granules, while the other set represents data taken from 0.5 regions centered on the cooler infalling intergranular material.  相似文献   

14.
High resolution OVRO CO 1–0 observations of the inner 30 in the LINER galaxy NGC 5218 reveal the presence of a double centrally peaked molecular concentration with extensions out to a radius of 12. The molecular mass detected is 2.4 × 109 M and the gas surface density is high, 3000 M pc square in the inner 500 pc. The SFR is 2–3 M yr–1 and the SFE is 13, which are low or moderate values for that gas surface density. We interpret the inner feature as a rotating molecular ring with a radius of 200 pc. We furthermore suggest that the LINER activity in NGC 5218 is not caused by an aging starburst, but by a buried AGN.  相似文献   

15.
On the basis of empirical (D)-dependency at the frequency of 5 GHz constructed using 15 planetary nebulae with the independently measured distances (10–171×10–20 W m–2 Hz–1 ster–1), we evaluated distances of 335 objects. Independent evidence of the correctness of the accepted scale are given. Then(D)-dependency is constructed and it is shown that atD<0.08 pc the mean electron density is higher than the one determined by the Seaton method. We showed that the filling factor diminishes with the increase of the PN diameter (1 atD0.08 pc and 0.2 atD0.4 pc). the ionized mass of 33 PNs is determined. With the diameter increase the ionized mass grows and atD0.4 pc reaches the valueM0.07M . We used the new distance scale when investigating the space distribution of PNs. The mean scale height =130±15 pc and the mean gradient of the change of surface densitym=0.37, which allowed us to estimate the total number of nebulae in the GalaxyN4×104. We divided the PNs according to their velocities (withV LSR>35 km s–1 andV LSR<35 km s–1) and permitted us to confirm that the PN belong to different sub-systems of the Galaxy. The estimated local formation rate of PNs [=(4.6±2.2)×10–12 pc–3 yr–1] is a little higher than the one of the white dwarfs. That can be explained by a large number of PNs having binary cores, which used in our sample. The statistical estimation of PN expansion velocity showed thatV ex increases from 5–7 km s–1 (atD0.03 pc) to 40–50 km s–1 (atD0.8 pc).  相似文献   

16.
On the persistence of the 22 y solar cycle   总被引：2，自引：0，他引：2  
We briefly discuss the existence of precise periodicities of the Hale cycle (-22 y), the Gleissberg cycle (-88 y), and -132 y cycle, in various direct and indirect indicators (as aurorae, 14C from tree rings and 10Be from polar ice) of solar activity. We consider also the behaviour of the 11y cycle and its first harmonic in modern sunspot series. It appears that the frequencies of -1 c/88 y and -1 c/132 y might be two subharmonics of the Hale cycle. The results support the hypothesis that the Sun behaves as a nonlinear system forced by an oscillator having the Hale frequency. The forcing element inside the Sun can be identified with a magnetofluid torsional oscillator.  相似文献   

17.
R. P. Lin 《Solar physics》1982,113(1-2):217-220
We present observations of an intense solar flare hard X-ray burst on 1980 June 27, made with a balloon-borne array of liquid nitrogen-cooled germanium detectors which provided unprecedented spectral resolution (1 keV FWHM). The hard X-ray spectra throughout the impulsive phase burst fitted well to a double power-law form, and emission from an isothermal 108–109K plasma can be specifically excluded. The temporal variations of the spectrum indicate that the hard X-ray burst is made up of two superposed components: individual spikes lasting 3–15 s, whch have a hard spectrum and a break energy of 30–65 keV; and a slowly varying component characterized by a soft spectrum with a constant low-energy slope and a break energy which increases from 25 keV to 100 keV through the event. The double power-law shape indicates that acceleration by DC electric fields parallel to the magnetic field, similar to that occurring in the Earth's auroral zone, may be the source of the energetic electrons which produce the hard X-ray emission. The total potential drop required for flares is typically 102 kV compared to 10 kV for auroral substorms.  相似文献   

18.
The solar causes of geomagnetic disturbances   总被引：1，自引：0，他引：1  
Geomagnetic disturbances have been identified with respect to their sources for 1977–1983. The disturbance level was found using the daily planetary index A p. High-amplitude ( 50), mean-amplitude (24) and low-amplitude ( 12) disturbances are caused by solar flares of importance 1, coronal holes, and filament cavities, respectively. The ranges of probable amplitudes of disturbances of different nature and their relative number are found from Poisson random distributions of amplitudes.  相似文献   

19.
The cooling effect of emission in the spectral lines, which dominates over continuous emission in the chromosphere and becomes important first around the temperature minimum, modifies greatly the radiative relaxation timet r in the solar atmosphere. This rises from low photospheric values to a maximum of 8 min just aboveT min, falls in the low chromosphere to 1.5 min because of line emission, but rises again to 6 min atT 7000–8400 K in the chromosphere where hydrogen ionization increases the specific heat.  相似文献   

20.
From an analysis of the interstellar extinction we conclude that interstellar grains are of three main kinds: graphite spheres of radii 0.02 m making up 10% of the total grain mass, small dielectric spheres of radius about 0.04 m making up 25% of the mass, and hollow dielectric cylinders containing metallic iron with diameters of 2/3 m making up 45% of the mass. The remaining 20% consists of other metals and metal oxides. The main dielectric component of the grains appears to be comprised of organic material.  相似文献   

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