共查询到20条相似文献，搜索用时 15 毫秒
1.
A filament with a very bright rim was observed in the H line on May 11, 1989, using the Meudon spectroheliograph. Absolute calibration of the spectroheliogram allows us to express the intensities in particular sites of the filament, in its bright rim and inside the surrounding chromosphere. From a large number of photometric scans, we obtained a histogram of the intensity excess of the bright rim relative to the quiet chromosphere. The mean value of this excess amounts to about 4%. We present a theoretical explanation of bright rims, based on the nature of H radiative diffusion in the filaments. Computed NLTE model of the filament leads to a rim intensity excess which is in good agreement with our observations. 相似文献
2.
Peter Foukal 《Solar physics》1971,19(1):59-71
A continuous relationship is proposed between the basic elements of the dark fine structure of the quiet and active chromosphere. A progression from chromospheric bushes to fibrils, then to chromospheric threads and active region filaments, and finally to diffuse quiescent filaments, is described. It is shown that the horizontal component of the field on opposite sides of an active region quiescent filament can be in the same direction and closely parallel to the filament axis. Consequently, it is unnecessary to postulate twisted or otherwise complex field configurations to reconcile the support mechanism of filaments with the observed motion along their axis. 相似文献
3.
We study the velocity fields in the region of quiet solar filaments using spectral observations at the Sayan Solar Observatory (ISTP, Irkutsk). Once the series of spectral images have been processed, maps of the two-dimensional distribution of the velocity and its variations in the chromosphere (in the Hβ λ = 486.13 nm line) and the photosphere (in the Fe I λ = 486.37 nm line) are constructed. The motions in the filaments have been found to consist of steady and periodic components. Our analysis of the spatial distributions of various oscillation modes shows that the short-period (<10 min) oscillations propagate mainly vertically and are observed at the filament edges, on scales of several arcseconds. The quasi-hour (>40 min) oscillations propagate mostly along the filament at a small angle to its axis. The intensity in the Hβ core in individual fragments of some filaments varies with a period of about one hour. The observed velocity structures in the filaments and the imbalance of steady motions on the opposite sides of the filaments can be explained in terms of the model of a twisted fine-structure magnetic flux tube. 相似文献
4.
The magnetic structure of arch filament systems 总被引：1，自引：0，他引：1
Edward N. Frazier 《Solar physics》1972,26(1):130-141
Photographic-type magnetograms are used in conjunction with H filtergrams to study the structure and evolution of magnetic fields associated with arch filament systems. The magnetograms show that the opposite ends of the arch filaments are indeed rooted in photospheric magnetic fields of opposite polarity. Furthermore, these magnetic field systems are in every case new magnetic flux appearing at the solar surface. Time lapse studies show the detailed process by which the flux tubes emerge through the surface. First, supergranules bring individual strands of magnetic flux to the surface and sweep the two feet of the flux tube to opposite sides of the supergranule. Then, the flux tube rises through the chromosphere, creating a visible arch filament. It is also shown that the observed rotation of the axis of an arch filament system in the plane of the solar surface is caused by the emergence of successive flux loops, each possessing different axial tilts. 相似文献
5.
Yngve Öhman 《Solar physics》1968,3(2):354-356
Observations are reported of an H filament clearly visible in the image of the chromosphere at the limb as well as in the H spectrum of the same part of the chromosphere. Observations of this kind may give valuable information about the absorption mechanism at work in filaments. 相似文献
6.
V. A. Krat 《Solar physics》1967,1(2):191-203
A new model is proposed for the solar chromosphere, which is assumed to be an instable inhomogeneous formation, consisting of numerous elements (filaments), each with different temperature and density. Fluctuations of the magnetic field may give rise to chromospheric turbulence and may also cause the chromospheric inhomogeneities.The chromosphere is suggested to consist of four discrete groups of filaments: (1) metallic filaments where the conditions for the emission of lines of neutral metals are optimal, (2) hydrogenic elements, with optimum conditions for the emission of the Balmer series of hydrogen, (3) helium filaments, with optimum conditions for the appearence of the neutral helium lines, (4) the subcoronal filaments, representing a transition from chromospheric to coronal formations.The metallic filaments may be further subdivided, first into filaments where the emission arises from scattering of photospheric radiation - these emit lines of neutral metals and of some metallic ions (CaII, SrII, and others), and further into filaments where the emission is farther from LTE conditions; the latter filaments are characterized by a somewhat higher electron temperature and by an electron density at least exceeding that of the other elements by an order of 10. Computations of the optimum conditions for the emission of the neutral helium lines were made with the aid of new tables of Sobolev. The helium filaments in the low chromosphere have lower temperatures and are denser than those in the upper chromosphere; for a part they may also be considered as hydrogen filaments. The derivation of the physical parameters of the subcoronal filaments was based on data on the Heii4686 chromospheric line emission and also on rocket observations of the ultraviolet solar spectrum. In order to evaluate the relative distribution of the various filaments between heights of 0 and 5000 km, data on the radio emission of the Sun at 8 mm are also used. Characteristics of the proposed model of the chromosphere are given in Table III and Figure 1. 相似文献
7.
A close temporal and spatial association has been found between erupting filaments/coronal transients and radio noise storm continua. The three transients studied occurred away from active regions and are members of a class not usually accompanied by chromospheric emission. The data analyzed were from the S-054 soft X-ray telescope on Skylab and from one- and two-dimensional interferometers at meter and decameter wavelengths at Nançay and Clark Lake observatories. Calculations confirmed that observed microwave radiation from the transients is due to thermal bremsstrahlung. The results are consistent with an interpretation of heating of an increased amount of coronal plasma by nonthermal, 10–100 keV electrons. Three possibilities for the source of the material are described: (1) The filament material; (2) evaporation from the chromosphere or transition region; and (3) via a long-lived reconnection process. 相似文献
8.
This paper presents a new method which allows for the automatic extraction and tracking of the evolution of filaments in solar images. Series of Hα full-disk images are taken in regular time intervals to observe the changes of the solar disk features. In each picture, the solar chromosphere filaments are identified for further evolution examination. Two alternative preprocessing techniques converting grayscale images into black-and-white pictures with enhanced chromosphere granularity are examined: local thresholding based on median values and global thresholding with brightness and area normalization. The next step employs morphological closing operations with multi-directional linear structuring elements to extract elongated shapes in the image. After logical intersection of directional filtering results, remaining noise is removed from the final outcome using morphological dilation and erosion with a circular structuring element. Experimental results show that the developed technique can achieve excellent results in detecting large filaments and good detection rates for small filaments. 相似文献
9.
Rakesh Mazumder 《天文和天体物理学研究(英文版)》2019,(6):43-50
A filament is a cool, dense structure suspended in the solar corona. The eruption of a filament is often associated with a coronal mass ejection(CME), which has an adverse effect on space weather. Hence,research on filaments has attracted much attention in the recent past. The tilt angle of active region(AR)magnetic bipoles is a crucial parameter in the context of the solar dynamo, which governs the conversion efficiency of the toroidal magnetic field to poloidal magnetic field. Filaments always form over polarity inversion lines(PILs), so the study of tilt angles for these filaments can provide valuable information about generation of a magnetic field in the Sun. We investigate the tilt angles of filaments and other properties using McIntosh Archive data. We fit a straight line to each filament to estimate its tilt angle. We examine the variation of mean tilt angle with time. The latitude distribution of positive tilt angle filaments and negative tilt angle filaments reveals that there is a dominance of positive tilt angle filaments in the southern hemisphere and negative tilt angle filaments dominate in the northern hemisphere. We study the variation of the mean tilt angle for low and high latitudes separately. Investigations of temporal variation with filament number indicate that total filament number and low latitude filament number vary cyclically, in phase with the solar cycle. There are fewer filaments at high latitudes and they also show a cyclic pattern in temporal variation. We also study the north-south asymmetry of filaments with different latitude criteria. 相似文献
10.
L. C. Garcia de Andrade 《Astrophysics and Space Science》2007,312(3-4):161-163
A new class of analytical solution of the coupled system of Da Rios-diffusion equation in magnetohydrodynamic (MHD) representing solitonic vortex filaments is obtained. One of the solutions is similar to the one found by Rogers and Schief describing a solitary wave propagating along a constant torsion vortex filament. Scalar magnetic diffusion equations are obtained by decomposing the magnetic filament along Frenet frame. The integral invariant of curvature is used to place limits on the diffused 100 eV plasma filament curvature. The resistivity of η=5×10?5 ohm?cm—close to the stainless steel limit is used to approximate the Frenet curvature. From the scalar diffusion equations the vortex filaments are constrained to move along torsionless (planar) trajectories. Da Rios equations are coupled to diffusion equation to obtain a solitonic vortex diffused filaments. Due to bounds in time and length L we show that the model discussed is particularly useful in solar physics. 相似文献
11.
1 ＩｎｔｒｏｄｕｃｔｉｏｎＩｔｉｓｎｏｗｗｅｌｌａｃｃｅｐｔｅｄｔｈｅｍａｇｎｅｔｉｃｆｉｅｌｄｉｎｆｉｌａｍｅｎｔｉｓｎｅａｒｌｙｈｏｒｉｚｏｎｔａｌａｎｄｔｈｅｃｏｍｐｏｎｅｎｔｏｆｔｈｅｆｉｅｌｄａｌｏｎｇｔｈｅｆｉｌａｍｅｎｔａｘｉｓｉｓｄｏｍｉｎａｎｔ (Ｄ啨ｍｏｕｌｉｎ ,1 997) .Ｗｈｅｎａｆｉｌａｍｅｎｔｉｓｐｒｅｓｅｎｔｉｎａｃｔｉｖｅｒｅｇｉｏｎ ,ｔｈｅｐｈｏｔｏｓｐｈｅｒｉｃｔｒａｎｓｖｅｒｓｅｆｉｅｌｄｂｅｎｅａｔｈｆｉｌａｍｅｎｔｍｏｓｔｌｙｌｉｅａｌｏｎｇｔｈｅｐｏｌａｒ… 相似文献
12.
Bruce W. Lites 《Solar physics》1980,68(2):327-337
Two years of data from the University of Colorado ultraviolet spectrometer aboard OSO-8 were searched for steady line-of-sight flows in the chromosphere and transition-zone above active regions. The most conspicuous pattern that emerges from this data set is that many sunspots show persistent blueshifts of transition-zone lines indicating velocities of about 20 km s–1 with respect to the surrounding plage areas. The data show much smaller shifts in ultraviolet emission lines arising from the chromosphere: the shifts are frequently to the blue, but sometimes redshifts do occur. Plage areas often show a redshift of the transition-zone lines relative to the surrounding quiet areas, and a strong gradient of the vertical component of the velocity is evident in many plages. One area of persistent blueshift was observed in the transition-zone above an active region filament. The energy requirement of these steady flows over sunspots is discussed. 相似文献
13.
Jiangtao Su Yu Liu Hiroki Kurokawa Xinjie Mao Shangbin Yang Hongqi Zhang Haimin Wang 《Solar physics》2007,242(1-2):53-63
We present new observations of the interactions of two close, but distinct, Hα filaments and their successive eruptions on
5 November 1998. The magnetic fields of the filaments are both of the sinistral type. The interactions between the two filaments
were initiated mainly by an active filament of one of them. Before the filament eruptions, two dark plasma ejections and chromospheric
brightenings were observed. They indicate that possible magnetic reconnection had occurred between the two filaments. During
the first filament eruption, salient dark mass motions transferring from the left erupting filament into the right one were
observed. The right filament erupted 40 minutes later. This second filament eruption may have been the result of a loss of
stability owing to the sudden mass injection from the left filament. Based on the Hα observations, we have created a sketch
for understanding the interactions between two filaments and accompanying activities. The traditional theory of filament merger
requires that the filaments share the same filament channel and that the reconnection occurs between the two heads, as simulated
by DeVore, Antiochos, and Aulanier (Astrophys. J.
629, 1122, 2005; 646, 1349, 2006). Our interpretation is that the external bodily magnetic reconnection between flux ropes of the same chirality is another
possible way for two filament bodies to coalesce.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
14.
P. C. Liewer E. M. De Jong J. R. Hall R. A. Howard W. T. Thompson J. L. Culhane L. Bone L. van Driel-Gesztelyi 《Solar physics》2009,256(1-2):57-72
A filament eruption, accompanied by a B9.5 flare, coronal dimming, and an EUV wave, was observed by the Solar TERrestrial Relations Observatory (STEREO) on 19 May 2007, beginning at about 13:00 UT. Here, we use observations from the SECCHI/EUVI telescopes and other solar observations to analyze the behavior and geometry of the filament before and during the eruption. At this time, STEREO A and B were separated by about 8.5°, sufficient to determine the three-dimensional structure of the filament using stereoscopy. The filament could be followed in SECCHI/EUVI 304 Å stereoscopic data from about 12 hours before to about 2 hours after the eruption, allowing us to determine the 3D trajectory of the erupting filament. From the 3D reconstructions of the filament and the chromospheric ribbons in the early stage of the eruption, simultaneous heating of both the rising filamentary material and the chromosphere directly below is observed, consistent with an eruption resulting from magnetic reconnection below the filament. Comparisons of the filament during eruption in 304 Å and Hα? show that when it becomes emissive in He II, it tends to disappear in Hα?, indicating that the disappearance probably results from heating or motion, not loss, of filamentary material. 相似文献
15.
Solar filaments exhibit a range of eruptive-like dynamic activity from the full, or partial, eruption of the filament mass
and surrounding magnetic structure, as a CME, to a fully confined dynamic evolution or “failed” eruption, sometimes producing
a flare but no CME. Additionally, observations of erupting filaments often show a clear helical structure, indicating the
presence of a magnetic flux rope. Dynamic helical structures, in addition to being twisted, frequently show evidence of being
kinked, with the axis of the flux rope exhibiting a large-scale writhe. Motivated by the fact that kinking motions are also
detected in filaments that fail to erupt, we investigate the possible relationship between the kinking of a filament and its
success or failure to erupt. We present an analysis of kinking in filaments and its implications for other filament phenomena
such as the nature of the eruption, eruptive acceleration, and post-eruptive re-formation. We elucidate the relationship between
kinking and the various filament phenomena via a simple physical picture of the forces involved in kinking together with specific
definitions of the types of filament eruption. The present study offers results directly applicable to observations, allowing
a thorough exploration of the implications of the observational relationship between kinking and filament phenomena and provides
new insight for modelers of CME initiation. 相似文献
16.
K. J. Li Q. X. Li P. X. Gao J. Mu H. D. Chen T. W. Su 《Journal of Astrophysics and Astronomy》2007,28(2-3):147-156
Long-term variation in the distribution of the solar filaments observed at the Observatorie de Paris, Section de Meudon from
March 1919 to December 1989 is presented to compare with sunspot cycle and to study the periodicity in the filament activity,
namely the periods of the coronal activity with the Morlet wavelet used. It is inferred that the activity cycle of solar filaments
should have the same cycle length as sunspot cycle, but the cycle behavior of solar filaments is globally similar in profile
with, but different in detail from, that of sunspot cycles. The amplitude of solar magnetic activity should not keep in phase
with the complexity of solar magnetic activity. The possible periods in the filament activity are about 10.44 and 19.20 years.
The wavelet local power spectrum of the period 10.44 years is statistically significant during the whole consideration time.
The wavelet local power spectrum of the period 19.20 years is under the 95% confidence spectrum during the whole consideration
time, but over the mean red-noise spectrum of α = 0.72 before approximate Carrington rotation number 1500, and after that the filament activity does not statistically show
the period. Wavelet reconstruction indicates that the early data of the filament archive (in and before cycle 16) are more
noiseful than the later (in and after cycle 17). 相似文献
17.
Makarov V. I. Stoyanova M. N. Sivaraman K. R. 《Journal of Astrophysics and Astronomy》1982,3(4):379-382
Ring-like filaments have been detected on the spectroheliograms in the H-alpha line. Inside these filaments the magnetic field
flux has a predominant polarity. Some of the dark filaments are connected by filament channels which can be seen at the limb
either as (a) weak prominences or (b) dense low chromospheric features or (c) multi-channel system of matter flow between
two prominences or (d) common quiescent prominences. The filament and the filament channel together form a continuous closed
contour and outline the region of thef polarity particularly at the beginning of the solar cycle. The change in sign of the polar field of the Sun is associated
with the drift of the filament band to high latitudes. 相似文献
18.
周道祺 《中国天文和天体物理学报》1991,(3)
在黑子半影电流的磁场中存在扰动不稳定模式,本文认为黑子半影纤维是由这种不稳定扰动发展而形成的,利用短波近似,分别在黑子半径方向及围绕黑子方向上求解非绝热慢波色散方程。由不稳定条件可得到(1)纤维的长度与宽度的数值;(2)纤维模式在长度方向上是静止的,在宽度方向上几乎是不动的;(3)半影纤维是黑子在重力场中的磁流特征之一;(4)半影纤维的出现,表示着黑子扭转磁场的存在。 相似文献
19.
In this paper we seek the origin of the axial component of the magnetic field in filaments by adapting theory to observations.
A previous paper (Mackay, Gaizauskas, and van Ballegooijen, 2000) showed that surface flows acting on potential magnetic fields
for 27 days – the maximum time between the emergence of magnetic flux and the formation of large filaments between the resulting
activity complexes – cannot explain the chirality or inverse polarity nature of the observed filaments. We show that the inclusion
of initial helicity, for which there is observational evidence, in the flux transport model results in sufficiently strong
dextral fields of inverse polarity to account for the existence and length of an observed filament within the allotted time.
The simulations even produce a large length of dextral chirality when just small amounts of helicity are included in the initial
configuration. The modeling suggests that the axial field component in filaments can result from a combination of surface
(flux transport) and sub-surface (helicity) effects acting together. Here surface effects convert the large-scale helicity
emerging in active regions into a smaller-scale magnetic-field component parallel to the polarity inversion line so as to
form a magnetic configuration suitable for a filament. 相似文献
20.
We propose a new model for the initiation of solar coronal mass ejections (CMEs) and CME-associated flares. The model is inferred from observations of a quiescent filament eruption in the north-western quadrant of the solar disk on 4 September 2000. The event was observed with the Siberian Solar Radio Telescope (5.7 GHz), the Nobeyama Radioheliograph (17 GHz) and SOHO/EIT and LASCO. Based on the observations, we suggest that the eruption could be caused by the interaction of two dextral filaments. According to our model, these two filaments merge together to form a dual-filament system tending to form a single long filament. This results in a slow upward motion of the dual-filament system. Its upward expansion is prevented by the attachment of the filaments to the photosphere by filament barbs as well as by overlying coronal arcades. The initial upward motion is caused by the backbone magnetic field (first driving factor) which connects the two merging filaments. Its magnetic flux increases slowly due to magnetic reconnection of the cross-interacting legs of these filaments. If a total length of the dual-filament system is large enough, then the filament barbs detach themselves from the solar surface due to magnetic reconnection between the barbs with oppositely directed magnetic fields. The detachment of the filament barbs completes the formation of the eruptive filaments themselves and determines the helicity sign of their magnetic fields. The appearance of a helical magnetic structure creates an additional upward-directed force (second driving factor). A combined action of these two factors causes acceleration of the dual-filament system. If the lifting force of the two factors is sufficient to substantially extend the overlying coronal magnetic arcade, then magnetic reconnection starts below the eruptive filament in accordance with the classical scheme, and the third driving factor comes into play. 相似文献