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1.
The properties of Doppler-velocity oscillations in solar faculae are analyzed at the photospheric level (based on Fe I 6569 ? and Fe I 8536 ? lines) and chromospheric level (based on Hα and Ca II 8542 ? lines) to search for upward propagating waves. The similarity of the averaged power spectra at 2.5–4 mHz is not found to be convincing proof of the presence of unidirectional wave-energy transfer from the photosphere to the chromosphere. Phase relations between the photospheric and chromospheric oscillations that are indicative of either upward or downward propagating waves are obtained for various areas in many faculae. This suggests that the wave energy of the five-minute oscillations returns to the photosphere, at least partially. The derived properties suggest that the role of faculae in the transfer of the five-minute oscillations to the chromosphere and overlying layers is not as obvious as could be expected. The relatively typical presence of low-frequency (0.5–2 mHz) oscillations in faculae and their possible important role in this energy transfer are noted.  相似文献   

2.
Five-second observations of the solar corona carried out in the FeIX 171 Å line by the KORONAS-FOTON instrument TESIS are used to study the dynamics of small-scale coronal structures emitting in and around coronal bright points. The small-scale structures of the lower corona display complex dynamics similar to those of magnetic loops located at higher levels of the solar corona. Numerous detected oscillating structures with sizes below 10 000 km display oscillation periods from 50 to 350 s. The period distributions of these structures are different for P < 150 s and P > 150 s, which implies that different oscillation modes are excited at different periods. The small-scale structures generate numerous flare-like events with energies 1024–1026 erg (nanoflares) and with a spatial density of one event per arcsecond or more observed over an area of 4 × 1011 km2. Nanoflares are not associated with coronal bright points, and almost uniformly cover the solar disk in the observation region. The ejections of solar material from the coronal bright points demonstrate velocities of 80–110 km/s.  相似文献   

3.
Recognizing that waves play an important role in energy-exchange processes between layers of the solar atmosphere, and that the characteristics of propagating waves are determined by the physical conditions of the medium, and, most importantly, the magnetic-field configuration, we have carried out a comparative analysis of the properties of oscillations in solar structures with various magnetic-field topologies: sunspots, faculae, and coronal holes. Simultaneous measurements of the Doppler velocities and intensities at the photospheric and chromospheric levels were accompanied by episodic measurements of the longitudinal magnetic field. In the chromosphere, spot umbrae dominate the three-minute oscillations, while lower-frequency modes are also observed in the penumbrae and at the outer parts of spots. Clear signs of propagating waves have been observed at the bases of coronal holes and in faculae only at frequencies close to 3 mHz.  相似文献   

4.
The magnetic-field structure in solar active regions outside spots is studied. The line-of-sight fields were measured using the new Crimean digital magnetograph in three spectral lines—Fe I 5253 Å, Fe II 5234 Å, and Ti I 5193 Å. Observations in the Fe II 5234 Å line indicate systematically higher field strengths than those in the Fe I 5253 Å line. The magnetic fluxes in 2″ elements are ～4.3×1018 Mx, ～4.6×1018 Mx, and ～6.2×1018 Mx according to the Fe I 5253 Å, Ti I 5193 Å, and FeII 5234 Å observations, respectively. Elements 2″–8″ in size make the largest contribution to the magnetic fluxes of active regions outside spots.  相似文献   

5.
SOHO/EIT data are used to analyze dimmings, or transient coronal holes (regions of reduced soft-X-ray and EUV emission), which are observed on the solar disk after halo-type coronal mass ejections (CMEs). Simultaneous observations in the 171 Å FeIX/X, 195 Å FeXII, and 284 Å FeIX coronal lines, which are sensitive to temperatures of T e ≈1.2, 1.5, and 2.0 MK, respectively, are considered, together with the 304 Å HeII transition-region line (T e ≈(0.02–0.08) MK). Difference images taken at intervals of six and twelve hours and compensated for solar rotation indicate that dimmings are normally strongly pronounced and have similar large-scale structures in the moderate-excitation-temperature 171 Å and 195 Å coronal lines, while the higher-temperature 284 Å line mainly display the deepest portions of the dimmings. In addition, clear dimmings with relatively small areas are visible in the 304 Å transition-region line during many CMEs, in particular, in regions adjacent to the source of the eruption. Moreover, dimmings in the transition region without coronal counterparts are observed during some events. These results suggest that the opening of magnetic-field lines and the resulting density reduction that occur during a CME can also involve cold plasma of the transition region. In addition, the effects of temperature variations cannot be ruled out for some dimming structures.  相似文献   

6.
Spectral variations of the nova V2468 Cyg were studied over 1.5 years following the beginning of its outburst, during its smooth fading and the star’s rebrightenings. Following the rebrightening on March 25, 2008, the profiles of H I lines had changed, from a two-component structure with peaks at ?220 and 670 km/s to a four-component structure with peaks at ?640, ?260, 255, and 620 km/s. The profiles of [N II] 5755 Å, [O III] 5007 Å, He II 4686 Å, and [Fe VII] 6086 Å lines varied throughout the interval of our observations. During rebrightenings, the lines profiles changed and the line intensities significantly decreased. The width of the [Fe VII] 6086 Å profile varied, in addition to its shape and intensity; this profile differed from the profiles of other lines during the nebular phase. Estimates of chemical-element abundances in the nova’s envelope indicate enhanced abundances of nitrogen and oxygen, compared to the Sun, and solar abundances of neon and argon. The helium abundance was somewhat higher than the solar value. The mass of the ejected envelope is estimated to be 5 × 10?5 M ⊙.  相似文献   

7.
Episodic observations of coronal holes were carried out simultaneously in several spectral lines during the 2002–2005 observational seasons. An analysis of eighteen time series is used to obtain the amplitude—spectral properties of oscillatory wave motions of the solar plasma at the bases of coronal holes. It is found that the amplitudes of the 5-min and 3-min line-of-sight velocity oscillations increase in coronal holes. Low-frequency (1–2 mHz) oscillations are concentrated at the boundaries of the chromospheric network, while the 3-mHz and 5-mHz oscillations dominate in the network cells. Clear indications of propagating waves have been found at the bases of coronal holes. The 3 mHz phase velocities are 45 ± 5 km/s and 80–100 km/s for the equatorial and polar coronal holes, respectively.  相似文献   

8.
New results from electrophotometric scanning of the solar disk in the HeI λ 10830 Å and Hα lines are presented. The intensity at the center of the HeI λ 10830.30 Å line is 1–3% higher in the regions of coronal holes than in quiescent regions; this is accompanied by a decrease in the size and contrast of the chromospheric network compared to the network in quiescent regions. Our observations in the HeI line revealed chains of “dark points” surrounding coronal holes. The Hα±0.5 observations show increased velocities of ascent near the dark points compared to the velocities inside coronal holes and in quiescent regions. It is proposed that the intensification and acceleration of the flows of solar plasma from the dark points are due to reconnection of the magnetic fields of the bipolar chromospheric network and the predominantly unipolar magnetic field inside the coronal holes. Our observations suggest that the same reconnection process takes place near the temperature minimum, in the presence of certain conditions at the boundary between coronal holes and bipolar active regions. The reconnection process produces plasma flows from the chromosphere to the corona, which are sufficient to form prominences.  相似文献   

9.
Large-scale solar disturbances associated with powerful flares and coronal mass ejections (CMEs) during two passages of a grand system of three active regions in October–November 2003 are analyzed using data obtained with the SOHO/EIT EUV telescope. Dimmings (transient coronal holes) and, to a lesser extent, coronal waves (traveling emitting fronts) are studied using fixed-difference derotated images, in which a correction for the solar rotation is applied and a single heliogram preceding the event is subtracted from all subsequent heliograms. This method allows us to study difference heliograms in both the 195 Å line (with an interval of 12 min) and the various-temperature channels of 171, 195, 284, and 304 Å (with an interval of six hours). Our analysis shows, in particular, that the disturbances associated with CMEs demonstrated a global character and occupied almost the entire southern half of the disk in virtually all eruptive events during the two solar rotations. At the same time, the northern half of the disk, which had a large coronal hole, was only slightly disturbed. The dominant dimmings were observed on the disk as narrow, long features stretched mainly between three main, well-separated regions of the system and as long structures located along lines of solar latitude in the south polar sector. For repetitive events with intervals between them being not so long, the dominant dimmings demonstrated a clear homology in their forms and locations. During the very powerful event of October 28, one homologous global set of dimmings changed to another set. Many dimmings were observed to be identical or very similar in the three coronal channels and the transition-region line. It follows from the analysis that rapidly recovering global structures in the corona and transition region were involved in the eruption of running CMEs and the corresponding reconstruction of the large-scale magnetic fields.  相似文献   

10.
A dynamical estimate of the mass of the black hole in the LMC X-1 binary system is obtained in the framework of a Roche model for the optical star, based on fitting of the He I 4471 Å and He II 4200 Å absorption lines assuming LTE. The mass of the black hole derived from the radial-velocity curve for the He II 4200 Å line is mx = 10.55 M⊙, close to the value found earlier based on a model with two point bodies [1].  相似文献   

11.
The differential rotation of the solar corona is studied using the brightness of the Fe XIV 530.3 nm green coronal line collected over 5.5 solar-activity cycles. The total observed velocity of the coronal rotation is analyzed as a superposition of two modes—fast and slow. A technique for separating two data series composing the initial data set and corresponding to the two differential-rotation modes of the solar corona is proposed. The first series is obtained by averaging the initial data set over six successive Carrington rotations; this series corresponds to long-lived, large-scale coronal regions. The second series is the difference between the initial data and the averaged series, and corresponds to relatively quickly varying coronal component. The coronal rotation derived from the first series coincides with the fast mode detected earlier using the initial data set; i.e., the synodic period of this mode is 27 days at the equator, then weakly increases with latitude, slightly exceeding 28 days at high latitudes. The second series describes a slow rotation displaying a synodic period of about 34 days. This coincides with the period of rotation of the high-latitude corona derived by M. Waldmeier for polar faculae. We expect that coronal objects corresponding to the fast mode are associated with magnetic fields on the scales typical for large activity complexes. The slow mode may be associated with weak fields on small scales.  相似文献   

12.
The X-ray luminosities and spectra of F-M stars of luminosity classes IV–V are analyzed. In dwarfs with rotational velocities of about 100 km/s, such as the optical components of low-mass X-ray novae with black holes, hot plasma can be confined in coronal loops even in the presence of fairly weak magnetic fields. Thus, the soft X-ray emission of such systems in their quiescent state (to 1031 erg/s) could be associated with the coronal emission of the optical component/dwarf. Two systems studied with subgiants (V1033 Sco and V404 Cyg) have X-ray luminosities 2×1032–2×1033 erg/s. The X-ray emission of a solar-type corona cannot provide such luminosities. However, a transition to a non-solar corona is possible in rapidly rotating subgiants—a dynamical corona whose X-ray emission can be one to two orders of magnitude higher than observed for more slowly rotating late-type subgiants in the solar neighborhood. This suggests that the quiescent X-ray emission of these two systems is provided by emission from the corona of the subgiant optical component.  相似文献   

13.
Data obtained with the EIT UV telescope and LASCO coronagraph of the SOHO satellite are used to analyze large-scale solar disturbances associated with a series of major flares and coronal mass ejections that occurred in the late decline phase of cycle 23, on November 3–10, 2004, and gave rise to strong geomagnetic storms. Derotated fixed-base difference heliograms taken in the 195 Å coronal channel at 12-min intervals and in the various-temperature 171, 195, 284, and 304 Å channels at 6-h intervals indicate that these disturbances were global and homologous; i.e., they had similar characteristics and affected the same structures. Almost all of the nine events of this series included two recurrent systems of large-scale dimmings (regions of reduced intensity with lifetimes of 10–15 h): (a) transequatorial dimmings connecting a northern near-equatorial eruption center with a southern active region and (b) northern dimmings covering a large sector between two coronal holes. In this northern sector, coronal waves (brightenings propagated from the eruption center at speeds of several hundred km/s) were observed ahead of the expanding dimmings. The brightest, central part of the halo-type coronal mass ejection in each event corresponded to the northern dimming system. The properties of the dimmings and coronal waves and the relationship between them are discussed on the basis of the results obtained. We find that the eruption of large coronal mass ejections involves structures of the global solar magnetosphere with spatial scales far exceeding the sizes of active regions and normal activity complexes.  相似文献   

14.
We analyze low-dispersion (1.8 Å per pixel) spectra of the recurrent nova RS Oph taken between the 10th and 241st days after its outburst on February 12, 2006. The spectra exhibit various stages in the development of the outburst, from its coronal phase to its nebular phase. We identified about 200 spectral lines at 3700–7500 Å, and fluxes were determined for the strongest lines. The spectral behavior of this outburst does not differ strongly from the previous one. One of the main differences is the presence of flux variations in the forbidden [NII] 5775 Å, [OI] 6300 Å, [OIII] 4959 Å, [OIII] 5007 Å, [KIV] 6101 Å, [FeVII] 6086 Å, and [FeX] 6375 Å lines, as well as in the HeI 5876 Å, HeI 6678 Å, HeII 4686 Å lines. We also obtained high-dispersion (0.06 Å per pixel) spectra in the region of the Hα and HeI 5876 Å lines between the 9th and 113th days after the outburst. The HeI 5876 Å profile has three components. This shape of the profile may result from the formation of an envelope after the aspherical explosion.  相似文献   

15.
Low-frequency pulsations of 22 and 37 GHz microwave radiation detected during solar flares are analyzed. Several microwave bursts observed at the Metsähovi Radio Observatory are studied with time resolutions of 100 and 50 ms. A fast Fourier transformation with a sliding window and the Wigner-Ville method are used to obtain frequency-time diagrams for the low-frequency pulsations, which are interpreted as natural oscillations of coronal magnetic loops; the dynamical spectra of the pulsations are synthesized for the first time. Three types of low-frequency fluctuations modulating the flare microwave radiation can be distinguished in the observations. First, there are fast and slow magneto-acoustic oscillations with periods of 0.5–0.8 s and 200–280 s, respectively. The fast magneto-acoustic oscillations appear as trains of narrow-band signals with durations of 100–200 s, a positive frequency drift dν/dt=0.25 MHz/min, and frequency splitting δν=0.01–0.05 Hz. Second, there are natural oscillations of the coronal magnetic loops as equivalent electrical circuits. These oscillations have periods of 0.5–10 s and positive or negative frequency drift rates dν/dt=8×10?3 Hz/min or dν/dt=?1.3×10?2 Hz/min, depending on the phase of the radio outburst. Third, there are modulations of the microwave radiation by short periodic pulses with a period of 20 s. The dynamical spectra of the low-frequency pulsations supply important information about the parameters of the magnetic loops: the ratio of the loop radius to its length r/L≈0.1, the plasma parameter β≈10?3, the ratio of the plasma densities outside and inside the loop ρe/ρi≈10?2, and the electrical current flowing along the loop I≈1012 A.  相似文献   

16.
The characteristic time scales for variations in the differential rotation of the solar corona are determined using measurements of the intensity of the FeXIV 5303 Å coronal line made from 1939–2004. Drift waves of the variations in the rotational speed with an 11-year periodicity can be distinguished. Moving averages with time intervals from two to five years are used to identify torsional waves. In addition, longer-period variations in the rotational speed can be distinguished when longer averaging intervals are used. When the interval used for the moving average is increased to 8–12 years, a quasi-22-year rotational period appears. The low-latitude corona rotates more slowly in odd cycles than in even cycles. Increasing the duration of the averaging interval further shows that rapid rotation at low latitudes was observed in 1940–1950 and 1990–2000, while slow rotation was observed in 1960–1980, possibly suggesting the presence of a 55-year period in the rotational variations. Long-term variations are found in the rotation of polar regions. The rotational variations for high-latitude corona are in antiphase with those for the low-latitude corona. The origins of zones of anomalous coronal rotation and their dynamics in the global activity cycle are discussed.  相似文献   

17.
The plane of polarization of the solar coronal emission on August 11, 1999   总被引：1，自引：0，他引：1  
A two-dimensional polarization image of the inner regions of the solar corona (R≤1.5R ?) during the total solar eclipse of August 11, 1999 is presented. This image clearly exhibits both small-and large-scale structure in the distribution of deviations of the plane of polarization from its theoretical direction for coronal emission in the near infrared (570–800 nm). An accuracy for the deviation angles of ≤1° was achieved by reducing the instrumental scattered light in the telescope, installing a continuously rotating polaroid near the image plane of the entrance pupil (i.e., the Lyot stop plane), and developing a special algorithm for constructing the polarization images based on the IDL software, in which the properties of the light are described in terms of the Stokes parameters. This algorithm was used to process 24 digitized polarization images of the corona, corresponding to one complete rotation of the polaroid. Analysis of the polarization image for angles of 0°–5° indicates the existence of significant deviations in the inner corona. The polar and equatorial coronal regions are characterized by diffuse and almost uniform structure of the deviation angles, 0.5° ± 0.5°, corresponding to Thomson scattering of the photospheric radiation by free electrons. Four large-scale structures over the NE, SE, NW, and SW limbs covering about 60° in position angle have deviations of 1°–3°. Numerous small-scale structures with dimensions up to 30″ and deviation angles of 3°–5° tracing strongly curved coronal streamers were detected in active coronal regions, especially over the NE limb. Interpretation of these deviations in terms of flows of moving electrons implies tangential velocities of up to 2.5×104 km/s, i.e., electron energies of up to 2×103 eV.  相似文献   

18.
Spatial and temporal variations in the line-of-sight velocities and brightnesses measured in the Hα and FeI 6564 Å Hβ and FeI 4864 Å NiI 4857 Å lines at the bases of polar coronal holes are analyzed. Time series with durations of 43–120 min were recorded using a CCD strip (3700 pixels 200×7 µm in size) and a CCD array (256×1024 pixels 24 µm in size). Quasi-stationary upward flows (with radial velocities reaching 3 km/s in the photosphere and 12–15 km/s in the chromosphere) were observed near dark points at the boundaries of the chromospheric network. The acoustic 3-min and 5-min oscillations are amplified in the coronal hole, and reach 1 km/s in the photosphere and 3–4 km/s in the chromosphere. The spectra of fluctuations of the line-of-sight velocity exhibit significant maxima at low frequencies, clustering near 0.4, 0.75, and 1 mHz.  相似文献   

19.
We present new spectroscopic observations of the peculiar supergiant IRC+10420. In 1997–2000, we obtained three high signal-to-noise ratio spectra of the object at 4300–8000 Å with a spectral resolution of 15 000 (20 km/ s) using the 6-m telescope of the Special Astrophysical Observatory. From our 2000 spectrum, we estimate the spectral type of IRC+10420 to be A2, corresponding to a temperature of ～9200 K. Many emission lines were detected, identified with lines of Fe I; Fe II, Ti II, Cr II, and Sc II ions; and [O I], [Fe II], and [Ca II] forbidden lines. The radial velocity derived from absorption lines without obvious emission components (He I λ5876, O I, N I, Si II) and from absorption components of the Balmer lines is 93±1 km/s. The redshift of photospheric lines relative to the star’s center-of-mass velocity is interpreted as a consequence of scattering in the expanding, optically thick dust envelope. Both emission and absorption lines show a correlation between radial velocity and oscillator strength. We found variability in the relative intensities of the H α and H β emission components. We conclude that IRC+10420 is rapidly evolving towards a Wolf-Rayet stage; the current rate of the photospheric temperature increase is ～120 K per year. Based on the intensity of the O I (λ7773) triplet, we estimate the star’s luminosity to be M bol=?9.5m. In all 1997–2000 spectra of IRC+10420, the He I λ5876 line has a significant equivalent width of at least 200 mÅ; this may be possible in the presence of such a low temperature due to the star’s high luminosity and the enhanced helium abundance in the supergiant’s atmosphere.  相似文献   

20.
The excitation of the ballooning instability by the eigenoscillations of coronal loops is analyzed using the energy method. The second variation of the potential energy for the case of a plasma—plasma boundary is obtained via the linearized ideal MHD equations. It is shown that the eigenmodes of a magnetic tube and of a toroidal coronal loop coincide in a first approximation. The bending oscillations of the loops are able to excite the ballooning instability when β ? 1. The effects of the instability in solar coronal loops are discussed.  相似文献   

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