共查询到10条相似文献，搜索用时 171 毫秒
1.
New results concerning prominence observations and in particular the prominence–corona transition region (PCTR) are presented. In order to cover a temperature range from 2 × 104 to 7 × 105 K, several emission lines in many different ionization states were observed with SUMER and CDS on board SOHO. EM and DEM were measured through the whole PCTR. We compared the prominence DEM with the DEM from other solar structures (active region, coronal hole and the chromosphere–corona transition region (CCTR)). We notice a displacement of the prominence DEM minimum towards lower temperatures with respect to the minimum of the other structures. Electron density and pressure diagnostics have been made from the observed C III lines. Local electron density and pressure for T ∼ 7 × 104 K are respectively log N
e = 9.30−0.34
+0.30 and 0.0405−0.014
+0.012. Extrapolations over the entire PCTR temperature range are in good agreement with previous SOHO results (Madjarska et al., 1999). We also provide values of electron density and pressure in two different regions of the prominence (center and edge). The Doppler velocity in the PCTR shows a trend to increase with temperature (at least up to 30 km s -1 at T ∼ 7 × 104 K), an indication of important mass flows. A simple morphological model is proposed from density and motion diagnostics. If the prominence is taken as a magnetic flux tube, one can derive an opening of the field lines with increasing temperature. If the prominence is represented as a collection of threads, their number increases with temperature from 20 to 800. Derived filling factors can reach values as low as 10−3 for a layer thickness of the order of 5000 km. The variation of non-thermal velocities is determined for the first time, in the temperature range from 2 × 104 to 7 × 105 K. The quite clear similarity with the CCTR non-thermal velocities would indicate that heating mechanisms in the PCTR could be the same as in the CCTR (wave propagation, turbulence MHD). 相似文献
2.
The statistical equilibrium equations for the continuum and first 10 levels of a hydrogen atom show that the radiation of a bright prominence (the brightness of the H line has attained 56 mÅ of the disc centre spectrum) is completely due to scattering of the Sun radiation. The basic unknowns are separated with certainty: electron concentration (n
e = 3.0 × 1010 cm–3), effective thickness (l = 4.2 × 108 cm) and electron temperature (T
e = 5000 K).Radiation of a very bright prominence (A
(H) = 213 mÅ; T
e = 7300 K; n
e = 5.0 × 1011 cm–3; l = 1.3 × 107 cm) is on account of electron impacts (40%) and the Sun radiation scattering (60%).The parameters are shown to depend greatly on the prominence optical thickness in the lines of the first subordinate series of a hydrogen atom. In the course of determination all the parameters and 100 interconnected integral equations of the radiation diffusion have been thickness-averaged; the population of levels has been calculated by observations using the self-absorption factors. 相似文献
3.
V. V. Krymkin 《Astrophysics and Space Science》1978,58(2):347-352
Observations of the ionized hydrogen region NGC 1499 have been carried out with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20 and 25 MHz. The half-power resolution of the instrument to zenith is 28×34 at 25 MHz. The average volume density of the non-thermal radio emission between the Sun and the nebula (1.75×10–40 W m–3 Hz–1 ster–1 at 25 MHz), the electron temperature of the HII nebula (T
e
=4400 K), the measure of emission (ME=1500 cm–6 pc) and other parameters have been obtained. Maps of brightness distribution over the source are presented for each observation frequency. The results are compared with previously obtained data. 相似文献
4.
We have investigated the effect of ionizing radiation from the UV stars (hot prewhite dwarfs) on the intergalactic medium (IGM). If the UV stars are powered only by gravitational contraction they radiate most of their energy at a typical surface temperature of 1.5×105 K which produces a very highly ionized IGM in which the elements carbon, nitrogen and oxygen are left with only one or two electrons. This results in these elements being very inefficient coolants. The gas is cooled principally by free-free emission and the collisional ionization of hydrogen and helium. For a typical UV star temperature ofT=1.5×105 K, the temperature of the ionized gas in the IGM isT
g
=1.2×105 K for a Hubble constantH
o=75 km s–1 Mpc–1 and a hydrogen densityn
H
=10–6 cm–3. Heating by cosmic rays and X-rays is insignificant in the IGM except perhaps inHi clouds because when a hydrogen atom recombines in the IGM it is far more likely to be re-ionized by a UV-star photon than by of the other two types of particles due to the greater space density of UV-star photons and their appreciably larger ionization cross-sections. If the UV stars radiate a substantial fraction of their energy in a helium-burning stage in which they have surface temperatures of about 5×104 K, the temperature of the IGM could be lowered to about 5×104 K. 相似文献
5.
We study the initiation and development of the limb coronal mass ejection (CME) of 15 May 2001, utilizing observations from Mauna Loa Solar Observatory (MLSO), the Solar and Heliospheric Observatory (SOHO), and Yohkoh. The pre-eruption images in various spectral channels show a quiescent prominence imbedded in the coronal void, being overlaid by the coronal arch. After the onset of rapid acceleration, this three-element structure preserved its integrity and appeared in the MLSO MK-IV coronagraph field of view as the three-part CME structure (the frontal rim, the cavity, and the prominence) and continued its motion through the field of view of the SOHO/LASCO coronagraphs up to 30 solar radii. Such observational coverage allows us to measure the relative kinematics of the three-part structure from the very beginning up to the late phases of the eruption. The leading edge and the prominence accelerated simultaneously: the rapid acceleration of the frontal rim and the prominence started at approximately the same time, the prominence perhaps being slightly delayed (4 – 6 min). The leading edge achieved the maximum acceleration amax 600 ± 150 m s–2 at a heliocentric distance 2.4 –2.5 solar radii, whereas the prominence reached amax 380± 50 m s–2, almost simultaneously with the leading edge. Such a distinct synchronization of different parts of the CME provides clear evidence that the entire magnetic arcade, including the prominence, erupts as an entity, showing a kind of self-similar expansion. The CME attained a maximum velocity of vmax 1200 km s–1 at approximately the same time as the peak of the associated soft X-ray flare. Beyond about 10 solar radii, the leading edge of the CME started to decelerate at a–20 m s–2, most likely due to the aerodynamic drag. The deceleration of the prominence was delayed for 10 –30 min, which is attributed to its larger inertia. 相似文献
6.
The masers of E-type methanol in orion KL and SGR B2 总被引：2，自引：0，他引：2
Using a simplified model the statistical equilibrium and radiative transfer equations of E-type-CH3OH are solved for Orion KL and SgrB2. According to our calculation results and the observation data taken by Matsakiset al. (1980) and Morimotoet al. (1985a, b), the physical conditions of both sources are estimated. In theJ
2-J
1 E methanol maser region of Orion KL, the density, kinetic temperature, dust temperature, and the fractional abundance are 0.8–2×106 cm–3, 150, 30–90 K, 0.8–8×10–6. In the 4–1-30 E and 5–1-40 E methanol maser region of Sgr B2 the correspondance physical conditions above are 104 cm3, 45, 23 K, and 7×10–7, respectively. 相似文献
7.
X-ray images have been studied quantitatively to determine electron temperature and density as functions of time in two long-decay X-ray enhancements (LDE's). This is the first study of the X-ray emission from LDE's to include all corrections for scattering and vignetting. Derived electron density is about twice that found by Vorpahl et al. (1977) and by Smith et al. (1977) in the same events. Our results are combined with those for two other LDE's to find their general characteristics. The LDE's all had the form of arcades of very bright loops which were 1–3 × 106 K hotter at the apices than along the legs. This temperature structure was maintained for at least 8 hr in each case. From this it is inferred that continual heating was taking place at the loop apices. Each LDE was preceded by a filament eruption and a white-light transient. Each was associated with a loop prominence system (LPS) composed of cool (T
e
< 105 K) loops nested 2–8 × 103 km below the hot LDE loops. And, although the energy release rates in the four events varied greatly even 4 hr after onset, they all had similar growth rates (loop height vs time 1 km s–1). Event lifetimes were very long, from 24 to 72 hr. After a survey of published models, it is concluded that only a magnetic reconnection model (e.g., Kopp and Pneuman, 1976) is consistent with these observations of the LDE-LPS phenomenon. 相似文献
8.
We present here the results of emission tomography studies, based on a new differential deconvolution method (DDM) of Laplace transform inversion, which we use for reconstruction of the coronal emission measure distributions in the quiet Sun, coronal holes and plage areas. Two methods are explored. The first method is based on the deconvolution of radioemission brightness spectra in a wide wavelength range (1 mm–100 cm) for temperature profile reconstructions from the corona to the deeper chromosphere. The second method uses radio brightness measurements in the cm–dm range to give a coronal column emission measure (EM).Our results are based on RATAN-600 observations in the range 2.0–32 cm supplemented by the data of other observatories during the period near minimum solar activity. This study gives results that agree with known estimates of the coronal EM values, but reveals the absence of any measurable quantities of EM in the transition temperature region 3 × 104 –105 K for all studied large-scale structures. The chromospheric temperature structure (T
e = 20,000–5800 K) is quite similar for all objects with extremely low-temperature gradients at deep layers.Some refraction effects were detected in the decimeter range for all Types of large-scale structures, which suggests the presence of dense and compact loops (up to N
e =(1–3)× 109 cm-3 number density) for the quiet-Sun coronal regions with temperature T
e > 5× 10-5 K. 相似文献
9.
Slit spectrograms of a quiescent prominence and the inner corona (h2.5 arc min) in the range 3400–7000 Å (dispersion 6–10 Å/mm) were obtained. From an analysis of the Stark effect on the Balmer lines (up to number 36) the electron density in the prominence n
e = (7 ± 3) × 1010 cm–3 was deduced. The kinetic temperature T
k and the non-thermal velocities
t, found from a simultaneous consideration of the Balmer and metal lines, are T
k 10 000 K and v
t6 km/s. Also the emission measure of the prominence along the line-of-sight was found: ME = 1031 cm–5.In the coronal spectrum 24 coronal lines were found. Thirteen of these lines were identified and measured photometrically to get their absolute intensities, profiles and halfwidths. For nine lines the intensities as a function of the height were studied and on this basis the coronal lines were divided into a few groups. The line-of-sight and non-thermal velocities are
r 10 km/s and
t 25 km/s. The coronal lines originate in at least three types of regions with different temperatures. The emission measure as a function of the ionization temperature was determined. The abundances of four elements of the iron group (V, Cr, Mn, Co) were estimated. The abundances of the other elements of the same group (A, Ca, Fe, Ni), found from EUV-data, are in a good agreement with our observations. The degree of inhomogeneity in the corona was estimated:
. 相似文献
10.
V. V. Krymkin 《Astrophysics and Space Science》1978,54(1):187-197
The results of observations of the Rosette emission nebula NGC 2237 with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20.0 and 25.0 MHz are given in the shape of contours of constant brightness temperature. The half-power beamwidth of the telescope to zenith at 25.0 MHz was 28×38. Density weighted mean values for the non-thermal radio emissivity between the Sun and the source (7.9×10–41 W m–3 Hz–1 ster–1 at 25.0 MHz) and the ratio of the intensity of emissivity generated before the area and the intensity of galactic radio emissivity appearing beyond the area equal to 1.3 have been obtained. The electron temperatureT
e=3600 K, the optical depth (about ten at 25 MHz), the measure of emission (ME=3500 cm–6 pc), the electron densityN
e=8 cm–3 and the nebular mass 16.6×10+3
M
have been determined. A comparison with other observation results has been made. 相似文献