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1.
Since 1986, we have made some improvements to the multichannel solar spectrograph at Purple Mountain Observatory (PMO) step by step, and now we have developed and added to it a multichannel infrared imaging solar spectrograph. The original spectrograph can be used to observe simultaneously solar activity at 9 wave bands including Caii H and K line, Mgi b line, Hei D3 line and H through H. The newly developed infrared imaging spectrograph can work in three wavelengths, i.e., Hei 10830 Å, Caii 8542 Å, and H. We replaced plates in the original system with CCDs and placed an image reducer before each CCD in order to match the CCD pixel size. The dispersions for Hei 10830 Å, Caii 8542 Å, and H of the new imaging solar spectrograph are 0.0693 Å, 0.0767 Å, and 0.0754 Å per CCD pixel respectively, and each vertical CCD pixel represents 0.34 arc sec of solar disk. We can obtain the line-center and off-band intensities of the three lines and the intensities of continua adjacent to these lines through the new instrument. We can also acquire velocity maps and line profiles. Therefore, it is specially suitable for two-dimensional (2D) spectroscopic observations of solar flares and active regions. We carry out scanning observation by rotating the second mirror of the coelostat system. In this paper, we introduce the improvements we made and the new imaging solar spectrograph. Some observation results are also presented in this article. 相似文献
2.
After carefully comparing the white-light (5600±00 Å) and the slit-jaw H images (0.5 Å passband) of the 2N/X20 white-light flare of 16 August 1989, we found that the H counterpart identification of the bright kernels in continuum by Hiei, Nakagomi, and Takuma (1992) was incorrect. Now we come to the conclusion that none of the two white-light kernels has a corresponding bright H area. Moreover, the loop shapes in white-light are also different from those in H. H loops rose more rapidly than white-light loops. However, their height–time variations on the whole are similar. This indicates that the continuum and chromospheric emissions of the flare presumably come from different plasmas, but may be modulated by some mutual factors, such as large-scale magnetic fields. Analysis of the Hei 10830 Å spectra taken simultaneously with the slit-jaw H images shows that the line-center intensity of Hei 10830 Å doesn't have a good correlation with the intensity of nearby continuum, which supports the above conclusions. In addition, the electron density at the white-light loop top estimated from the continuum around 5600 Å and 10830 Å is as high as 1012–1013 cm–3. 相似文献
3.
Skomorovsky V.I. Firstova N.M. Kashapova L.K. Kushtal G.I. Boulatov A.V. 《Solar physics》2001,199(1):37-45
A new two-bandpass birefringent filter has been produced at ISTP, Irkutsk for the investigation of the fine structure of the chromosphere. One filter passband is centered on the Hei 10830 Å line, the second one is centered on H. The FWHM of the Hei 10830 Å passband is 0.46 Å and of the H passband is 0.3 Å. A large number of filtergrams were obtained with the filter at the Sayan observatory. At the same time, spectral observations with high spatial and spectral resolution were carried out by the large solar vacuum telescope at the Baikal Observatory. We selected 29 `dark point' spectra with sizes from 2 to 13, as well as `dark points' on the filtergrams. Comparison of spectrograms and filtergrams has shown a good agreement of their size and intensity in relation with the surrounding chromosphere as well as the absence of primary line-of-sight velocities in both observation types. From spectral observations, the depth of 10830 Å is over 30% for some `dark points', and the FWHM is more than 1 Å. Hei 10830 Å line profiles in `dark points' are more deep and wide than in quiet regions. The optical depth of the chromosphere in `dark points' is estimated. Comparison with the unperturbed chromosphere showed that `dark points' in Hei 10830 Å are more optically thin than the nearby chromosphere. 相似文献
4.
In this letter, we bring attention to prominences which show different morphology in H and Heii 304 Å, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two kinds of anomaly: (1) prominences showing strong H emissions in the lower part and strong Heii emissions in the upper part, and (2) erupting prominences showing extensive Heii emission, but nothing in H. Our results indicate that a part or the whole of a prominence may be too hot to emit H radiation, possibly due to heating or thermal instability. Please note that these are not just two isolated cases, many other prominences show the similar differences in H and Heii 304 Å. 相似文献
5.
The profiles of six photospheric absorption spectral lines (Fei 5250 Å, Fei 5324 Å, Fei 5576 Å, Cai 5590 Å, Cai 6103 Å and Fei 6165 Å), measured in the kernel of a 2N solar flare and in a quiet-Sun area, were compared. The observations were carried out with an echelle spectrograph of the Crimean Astrophysical Observatory. It was shown that, compared to the quiet-Sun profiles, the flare profiles are shallower in the line core and are less steep in the wings. Therefore, measurements of the longitudinal magnetic field made with a magnetograph system which uses the Cai 6103 Å spectral line, can be underestimated by 18–25% in areas of bright H ribbons of a moderate solar flare. Modeling of the solar photosphere performed by using a synthesis method showed that, in a solar flare, the enhanced core emission seems to be related to heating of the photosphere by the flare, whereas the decrease of the slope of the wings was presumably caused by the inhomogeneity of the photospheric magnetic field. 相似文献
6.
The 3N/X3.3 flare of 28 November 1998 was observed in multiple wavelength simultaneously. The available data include H images, spectra in Hei 1083 nm and Caii 854.2 nm from Purple Mountain Observatory (PMO), soft X-ray (SXR) and hard X-ray (HXR) images and flux from Yohkoh. Morphological relationship investigation and spectral analysis of these data show: (1) The sudden brightening at loop top above the active region and the steep increase of SXR flux before flare onset suggest that the corona there had already been heated to some extent in the preflare phase. (2) The scales of the Caii 854.2 nm emission areas are very similar to those of the H line, but the emission profiles look like those of the Caii K line. Most of the Hei 1083 nm emissions exist in the bright H kernels and can last to the decay phase. (3) Flare spectra show that line shift and asymmetry are very common in this flare not only in the impulsive phase but also in the decay phase. The difference in the line shifts or asymmetry between Caii 854.2 nm and Hei 1083 nm, as well as the difference between the line center and wings of Caii 854.2 nm imply the existence of a velocity gradient in the line-of-sight direction. (4) Post-flare loops with very deep absorption (70%) and very-high-velocity red shifts (30–90 km s–1) were observed in Hei 1083 nm during the decay phase. However, only a slight dip can be found in the Caii 854.2 nm profile. 相似文献
7.
Solar Wind Velocity and Anisotropic Coronal Kinetic Temperature Measured with the O Vi Doublet Ratio
Doppler dimming of the Ovi resonance lines (1032 Å, 1037 Å) in an expanding corona is calculated including the pumping effect on the Ovi 1037.61 Å of both Cii lines at 1036.34 Å and 1037.02 Å, and the effect of the width of the absorption profiles of the coronal oxygen ions along the incident radiation. The pumping effect of the Cii line at 1036.34 Å allows us to extend to approximately 450 km s–1 the measurement of solar wind velocities with the Ovi line ratio technique. Since the emissivity ratio of the Ovi doublet depends on the width of the oxygen coronal absorbing profiles, this ratio can provide an accurate measurement of the solar wind velocity in the case that the width of the absorbing profile along the direction of the incident radiation is independently determined. However, if on the one hand the ratio of the emissivities of the Ovi doublet has limitations in probing the wind velocity, on the other hand it can be used as a diagnostics for inferring the velocity distribution of the coronal Ovi ions along the radial, and detecting possible velocity anisotropies. This diagnostics, applied to recent observational results, allows us to infer that the velocity distribution of the oxygen ions is much broader in the direction perpendicular to the magnetic field direction, and that the acceleration of the fast solar wind in the first 2 solar radii is high. 相似文献
8.
R-matrix calculations of electron impact excitation rates in Nixviii are used to derive theoretical electron-temperature-sensitive emission line ratios involving 3s–4p,3p–4d,3p –4s, and 3d–4f transitions in the 41–53 Å wavelength range. A comparison of these with solar flare observations from a rocket-borne X-ray spectrograph (XSST) reveals generally excellent agreement between theory and experiment (within the experimental and theoretical uncertainties), which provides support for the atomic data adopted in the analysis. However the 3s 2S–4p 2P1/2 line of Nixviii at 41.22 Å appears to be blended with the Fexix 13.74 Å feature observed by XSST in third order. In addition, the measured Nixviii intensity ratio I(3p 2P3/2– 4s 2S)/I(3p 2P1/2–4s 2S)=I(51.02 Å)/I(50.26 Å)=0.56, a factor of 3.8 smaller than the theoretical (temperature and density-insensitive) value of 2.1. The reason for this discrepancy is currently unexplained, but is unlikely to be due to blending of the 50.26 Å line, as the intensity of this feature is consistent with that expected from the other Nixviii lines in the XSST spectrum. Future observations of the Nixviii lines by the Advanced X-ray Astrophysics Facility (AXAF) should allow this problem to be resolved, and may also permit the use of the lines as electron-temperature diagnostics. 相似文献
9.
On 27 September 1998, Big Bear Solar Observatory (BBSO) and Transition Region and Coronal Explorer (TRACE) coordinated observations from 16:00 to 19:00 UT to study properties of microflares in AR NOAA No. 8340. Fortuitously, a C5.2 flare occurred at 16:30 UT in this active region. H and magnetograph movies were obtained at BBSO; Civ 1550 Å, Feix 171 Å, and Fexii 195 Å movies were obtained by TRACE; both with a cadence about 1 min. In this paper, we concentrate on the study of magnetic properties of 70 Civ microflares, as well as their relationship to the C5.2 flare. We obtained the following results: (1) We found two kinds of microflares: microflares of transient brightenings with a time scale of 1 to 5 min (impulsive events) and microflares lasting half an hour or longer (persistent events). Ninety percent of the microflares are impulsive events. Most of the event in this category are associated with well defined magnetic neutral lines, but some are found in non-neutral line areas. All of seven persistent events are found at parasitic magnetic configurations with inclusions of small magnetic flux within dominant magnetic flux of opposite polarity. (2) More than a third of the impulsive microflares occurred near the C5.2 flare site indicating that a local instability is responsible for both the C5.2 flare and microflares. This indirectly supports the avalanche theory of flare energy release, which implies that a big flare may be spatially associated with many small flares. 相似文献
10.
Blanco S. Bocchialini K. Costa A. Domenech G. Rovira M. Vial J.-C. 《Solar physics》1999,186(1-2):281-290
We have studied through a multiresolution wavelet analysis the oscillations in a limb prominence. Intensity fluctuations in time and height corresponding to different lines of Siiv and Oiv observed with SUMER on board SOHO have been analyzed in the wavelet bands of J3= 1 min 36 s to 3 min 12 s and J4=3 min 12 s to 6 min 24 s. For all species, oscillations in the J4 band were dominant. We found relevant differences between the behavior of line D1 (1393.76 Å) corresponding to Siiv and the set D2 (1401.16 Å), D3 (1404.81 Å), D4 (1402.77 Å) corresponding to Oiv, Oiv and Siiv respectively. We also report the identification of a pulse in the intensity of the line D1 that appears in the range of 15–20 min. This disturbance seems to travel with a speed of about 170 km s–1. 相似文献
11.
In this paper we present the results of inversion of Stokes polarization profiles of a sunspot, to recover the vector magnetic field parameters of the spectral-line-forming region, using the Fei 5324.19 Å line and a nonlinear least-squares fitting. Observations of the simple sunspot were obtained using the Video Vector Magnetograph at the Huairou Solar Observing Station (HSOS) of the National Astronomical Observatories of China, over the wavelength interval of 150 mÅ redward of line center of Fei 5324.19 Å to 150 mÅ to the blue, in steps of 10 mÅ. The curves of the observed variation of azimuth with wavelength are also compared with model calculations of the azimuth at each wavelength, as derived from the inverse Zeeman effect modified by Faraday rotation. The results show that the rotation of azimuth is less significant in the observations taken near the center of the Fei 5324.19 Å line than those taken near the center of the Fei 5250.22 Å line. 相似文献
12.
Lorenzo Iorio 《Celestial Mechanics and Dynamical Astronomy》2001,79(3):201-230
The general relativistic Lense—Thirring effect can be measured by inspecting a suitable combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. The solid and ocean Earth tides affect the recovery of the parameter by means of which the gravitomagnetic signal is accounted for in the combined residuals. Thus an extensive analysis of the perturbations induced on these orbital elements by the solid and ocean Earth tides is carried out. It involves the l=2 terms for the solid tides and the l=2,3,4 terms for the ocean tides. The perigee of LAGEOS II turns out to be very sensitive to the l=3 part of the ocean tidal spectrum, contrary to the nodes of LAGEOS and LAGEOS II. The uncertainty in the solid tidal perturbations, mainly due to the Love number k
2, ranges from 0.4% to 1.5%, while the ocean tides are uncertain at 5–15% level. The obtained results are used in order to check in a preliminary way which tidal constituents the Lense-Thirring shift is sensitive to. In particular it is tested if the semisecular 18.6-year zonal tide really does not affect the combined residuals. It turns out that, if modeled at the level of accuracy worked out in the paper, the l=2,4 m=0 and also, to a lesser extent, the l=3, m=0 tidal perturbations cancel out.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
13.
Based on EUV observations of eleven sunspot regions obtained with the Coronal Diagnostic Spectrometer, CDS, on SOHO we have studied the spatial distribution, temporal variation and wavelength shift of the Hei 584 line. We find a relatively high spatial correlation between the coronal line Fexvi 360 and the Hei 584 line. This points to coronal back-radiation as an important contributor to the formation of the Hei line in active regions. However, contribution to the line formation from another source is suggested by the following two findings: First, the red-shifted line profiles of both Hei 584 and the transition region lines tend to be more intense than blue-shifted profiles. Second, the Hei 584 emission changes significantly faster than the coronal line emission. 相似文献
14.
G. Contopoulos M. Harsoula N. Voglis 《Celestial Mechanics and Dynamical Astronomy》2000,78(1-4):197-210
We find the form of cantori surrounding an island of stable motion in the standard map for various values of the nonlinearity parameter K near the value K=5 (much larger than the critical value K
cr=0.971635...). The asymptotic curves of unstable periodic orbits inside the cantorus cross it after a certain time and then escape to the large chaotic sea. For K=5 the crossing time (in appropriate units) is t=1 and the escape time is t=2. For K=4.998 the crossing time is t=7 and the escape time t=23000. This delay of escape is due to the existence of higher order cantori, with very small gaps. We found that, as K increases the noble torus [2,4,1,1,..] is destroyed before the destruction of the higher order tori [2,4,1,1,1,1,2,1,...] and [2,4,1,1,1,1,3,1,...]. Thus the torus with the simplest noble number is not the last KAM curve to be destroyed. Then we find that nearby orbits deviate considerably, but the average times spent near various resonance before escape are very similar. 相似文献
15.
The observed distribution of waiting times t between X-ray solar flares of greater than C1 class listed in the Geostationary Operational Environmental Satellite (GOES) catalog exhibits a power-law tail (t) for large waiting times (t>10hours). It is shown that the power-law index varies with the solar cycle. For the minimum phase of the cycle the index is =–1.4±0.1, and for the maximum phase of the cycle the index is –3.2±0.2. For all years 1975–2001, the index is –2.2±0.1. We present a simple theory to account for the observed waiting-time distributions in terms of a Poisson process with a time-varying rate (t). A common approximation of slow variation of the rate with respect to a waiting time is examined, and found to be valid for the GOES catalog events. Subject to this approximation the observed waiting-time distribution is determined by f(), the time distribution of the rate . If f() has a power-law form for low rates, the waiting time-distribution is predicted to have a power-law tail (t)–(3+) (>–3). Distributions f() are constructed from the GOES data. For the entire catalog a power-law index =–0.9±0.1 is found in the time distribution of rates for low rates (<0.1hours
–1). For the maximum and minimum phases power-law indices =–0.1±0.5 and =–1.7±0.2, respectively, are observed. Hence, the Poisson theory together with the observed time distributions of the rate predict power-law tails in the waiting-time distributions with indices –2.2±0.1 (1975–2001), –2.9±0.5 (maximum phase) and –1.3±0.2 (minimum phase), consistent with the observations. These results suggest that the flaring rate varies in an intrinsically different way at solar maximum by comparison with solar minimum. The implications of these results for a recent model for flare statistics (Craig, 2001) and more generally for our understanding of the flare process are discussed. 相似文献
16.
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
17.
Morphological differences between coronal images on the one hand, and a Hei image on the other, are used to demonstrate the independence of Heii excitation from coronal radiation. The distribution of magnetic flux is found to be more important for Heii excitation. Collisional excitation by non-thermal electrons produced in nano-flare events is proposed as the mechanism for Heii excitation. 相似文献
18.
By solving the Euler hydrodynamical equations we have obtained closed form solutions for the angular velocities and pressures of a three stratified non-confocal heterogeneous oblate spheroid. Limiting and particular solutions cases, such as a spheroid with N layers, a stratified spheroid with the same eccentricities, as well as confocal layered spheroids are also explicitly written down. As an application, we have numerically estimated planet Earth's outer and inner cores' ellipticities to be o=1/413.318 and i=1/424.616, respectively. These Earth's ellipticities values are in good agreement with those found in the literature. 相似文献
19.
Solar flares,microflares, nanoflares,and coronal heating 总被引：2，自引：0，他引：2
H. S. Hudson 《Solar physics》1991,133(2):357-369
Solar flare occurrence follows a power-law distribution against total flare energy W: dN/dW W
– with an index 1.8 as determined by several studies. This implies (a) that microflares must have a different, steeper distribution if they are energetically significant, and (b) there must be a high-energy cutoff of the observed distribution. We identify the distinct soft distribution needed for coronal heating, if such a distribution exists, with Parker's nanoflares.This paper considers a microflare to be a member of the normal X-ray burst population, with comparable physical parameters except for a smaller total energy. 相似文献
20.
We obtained a complete set of H, Ca 8542 and He I 10830 spectra and slit-jaw H images of the C5.6 limb flare of 1 August 2003 using the Multi-channel Infrared Solar Spectrograph (MISS) at Purple Mountain Observatory. This flare was also observed by the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and partially by the Extreme-ultraviolet Imaging Telescope (EIT) on SOHO. This flare underwent a rapid rising and expanding episode in the impulsive phase. All the H, Ca 8542 and He I 10830 profiles of the flare are rather wide and the widest profiles were observed in the middle bright part of the flare instead of at the flare loop top near the flare maximum. The flare manifested obvious rotation in the flare loop and the decrease of the rotation angular speed with time at the loop-top may imply a de-twisting process of the magnetic field. The significant increases of the Doppler widths of these lines in the impulsive phase reflect quick heating of the chromosphere, and rapid rising and expanding of the flare loop. The RHESSI observations give a thermal energy spectrum for this flare, and two thermal sources and no non-thermal source are found in the reconstructed RHESSI images. This presumably indicates that the energy transfer in this flare is mainly by heat conduction. The stronger thermal source is located near the solar limb with its position unchanged in the flare process and spatially coincident with the intense EUV and H emissions. The weaker one moved during the flare process and is located in the H dark cavities. This flare may support the theory of the magnetic reconnections in the lower solar atmosphere. 相似文献