共查询到20条相似文献，搜索用时 31 毫秒
1.
David L. Glackin 《Solar physics》1974,36(1):51-60
The latitudinal component of solar differential rotation and the possibility of a radial component are discussed and compared to the observed rotational velocities of solar filaments. Our values of rotational rate versus heliographic latitude for 100 points in the solar atmosphere derived from 17 quiescent filaments are comparable to the rates found by d'Azambuja and d'Azambuja (1948). The filament rate is significantly greater than the spot rate (Newton and Nunn, 1951); the difference cannot be accounted for by the poleward migration of filaments and seems to reflect a true radial gradient of rotational velocity in the Sun. We show that filaments in closer proximity to active regions usually exhibit no differential rotation, while those far from active regions generally show it clearly. Comparison with Mt. Wilson photospheric Doppler measurements shows that filaments rotate faster than the general photosphere and that, as is well known, the spot rate exceeds that for the general photosphere. 相似文献
2.
By tracing the positions of filaments on the solar disk for a series of consecutive Carrington rotations, one can make a compact representation of the changes in general topology of photospheric magnetic fields during the course of a solar cycle. Examples are shown for the time period 1964–1974, which may provide some insight into the long-term relationship of the mid-latitude diagonal filaments and the high latitude polar crown. 相似文献
3.
The Carte Synoptique catalogue of solar filaments from 1919 March to 1957 July, corresponding to complete cycles 16‐18, is utilized to show the latitudinal migrations of solar filaments at low (≤50°) and high (>50°) latitudes and the latitudinal distributions of solar filaments for all solar filaments, solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° and solar filaments whose maximum lengths during solar disk passage are larger than 70°. The results show the following. (1) The latitudinal migrations of all low‐latitude solar filaments and low‐latitude solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° follow the Spörer sunspot law. However, the latitudinal migration of low‐latitude solar filaments whose maximum lengths during solar disk passage are larger than 70° do not follow the Spörer sunspot law: there is no equatorward and no poleward drift. The latitudinal migration of high‐latitude solar filaments whose maximum lengths during solar disk passage are larger than 70° is more significant than those of all high‐latitude solar filaments and high‐latitude solar filaments whose maximum lengths during solar disk passage are less than or equal to 70°: there is a poleward migration from the latitude of about 50° to 70° and an equatorward migration from the latitude of about 70° to 50° of all high‐latitude solar filaments and high‐latitude solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° and there is a poleward migration from the latitude of about 50° to 80° and an equatorward migration from the latitude of about 80° to 50° of high‐latitude solar filaments whose maximum lengths during solar disk passage are larger than 70°. (2) The statistical characteristics of latitudinal distribution of solar filaments whose maximum lengths during solar disk passage are larger than 70° is different from those of all solar filaments and solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
太阳暗条作为太阳大气磁场的示踪,对研究太阳磁场有极其重要的意义。针对现有的暗条检测方法存在检测精度不高,弱小暗条错检、漏检等问题,提出一种基于改进VNet网络的太阳暗条检测方法。首先,使用大熊湖天文台Hα全日面图像并结合磁图制作了太阳暗条数据集;其次,在VNet网络下采样部分采用Inception模块融合不同尺度特征图的特征,同时加入注意力机制增强特征图中暗条部分的语义信息;最后在上采样部分引入深度监督模块,更多地保留太阳暗条的细节特征。为验证算法性能,采用191幅Hα全日面图像数据集,其中包含暗条共3372条。算法在测试数据集上平均准确率达到0.9883,F1值达到0.8385。实验结果证明,该方法可以有效识别Hα全日面图中的暗条。 相似文献
5.
The periodicity of high-latitude solar activity has been studied with the use of the Carte Synoptique solar filaments archive.
The Morlet wavelet is utilized to analyze the periodicity of the number of solar filaments at latitudes over 50° during Carrington
solar rotations 876 – 1823. For solar filaments at latitudes over 50°, the most eminent periods are about 10.23 and 10.90
years, which correspond to the Schwabe period of high-latitude solar activity, and the these periods make-up a highly significant
proportion of the time span considered. The periods of 1.3 and 1.7 years and the quasi-biennial 2 – 3-year oscillation often
mentioned in the literature are not found to be a feature of every solar cycle but seem to appear only from time to time. 相似文献
6.
Vršnak B. Roša D. Božić H. Brajša R. Ruždjak V. Schroll A. Wöhl H. 《Solar physics》1999,185(2):207-225
Two large stable solar filaments were used as test tracers to determine the apparent synodic rotation rate as a function of the central meridian distance for several filaments' segments at different heights. An analytic fitting procedure was applied to determine simultaneously the real synodic rotation rate and the height of the traced filament segments. The determined heights were compared with the values obtained from the widths of filament contours on the solar disk and with the values obtained by direct measurements at the solar limb. Furthermore, the obtained rotation rates and heights of the filaments' segments close to the filaments' pivot points were compared with the values obtained using two successive central meridian passages. Finally, sources and scales of errors were investigated and possible implications on the previous studies of the solar differential rotation were considered. 相似文献
7.
《天文和天体物理学研究(英文版)》2020,(10)
Solar filaments are an intriguing phenomenon, like cool clouds suspended in the hot corona.Similar structures exist in the intergalactic medium as well. Despite being a long-studied topic, solar filaments have continually attracted intensive attention because of their link to coronal heating, coronal seismology, solar flares and coronal mass ejections(CMEs). In this review paper, by combing through the solar filament-related work done in the past decade, we discuss several controversial topics, such as the fine structures, dynamics, magnetic configurations and helicity of filaments. With high-resolution and highsensitivity observations, combined with numerical simulations, it is expected that resolving these disputes will definitely lead to a huge leap in understanding the physics related to solar filaments, and even shed light on galactic filaments. 相似文献
8.
We developed a method to automatically detect and trace solar filaments in Hα full-disk images. The program is able not only to recognize filaments and determine their properties, such as the position, the area, the spine, and other relevant parameters, but also to trace the daily evolution of the filaments. The program consists of three steps: First, preprocessing is applied to correct the original images; second, the Canny edge-detection method is used to detect filaments; third, filament properties are recognized through morphological operators. To test the algorithm, we successfully applied it to observations from the Mauna Loa Solar Observatory (MLSO). We analyzed Hα images obtained by the MLSO from 1998 to 2009 and obtained a butterfly diagram of filaments. This shows that the latitudinal migration of solar filaments has three trends in Solar Cycle 23: The drift velocity was fast from 1998 to the solar maximum, after which it became relatively slow. After 2006, the migration became divergent, signifying the solar minimum. About 60 % of the filaments with latitudes higher than 50° migrate toward the polar regions with relatively high velocities, and the latitudinal migrating speeds in the northern and the southern hemispheres do not differ significantly in Solar Cycle 23. 相似文献
9.
Solar filaments show the position of large-scale polarity-inversion lines and are used for the reconstruction of large-scale
solar magnetic field structure on the basis of Hα synoptic charts for the periods that magnetographic measurements are not
available. Sometimes crossing filaments are seen in Hα filtergrams. We analyze daily Hα filtergrams from the archive of Big
Bear Solar Observatory for the period of 1999 – 2003 to find crossing and interacting filaments. A number of examples are
presented and filament patterns are compared with photospheric magnetic field distributions. We have found that all crossing
filaments reveal quadrupolar magnetic configurations of the photospheric field and presume the presence of null points in
the corona. 相似文献
10.
This paper presents a generic method to automatically segment and characterize solar filaments from various Hα full-disk solar
images, obtained by different solar observatories, with different dynamic ranges and statistical properties. First, a cascading
Hough circle detector is designed to find the center location and radius of the solar disks. Second, polynomial surface fitting
is adopted to correct unbalanced luminance. Third, an adaptive thresholding method is put forward to segment solar filaments.
Finally, for each piece of a solar filament, its centroid location, area, and length are characterized, in which morphological
thinning and graph theory are used for identifying the main skeletons of filaments. To test the performance of the proposed
methods, a dataset composed of 125 Hα images is considered. These images were obtained by four solar observatories from January
2000 to May 2010, one image per month. Experimental results show that the accuracy rate is above 95% as measured by filament
number and above 99% as measured by filament area, indicating that only a few tiny filaments are not detected. 相似文献
11.
The 180-degree ambiguity in magnetic field direction along polarity reversal boundaries can be resolved often and reliably
by the chiral method. The chiral method requires (1) identification of the chirality of at least one solar feature related
to a polarity reversal boundary along which the field direction is sought and (2) knowledge of the polarity of the network
magnetic field on at least one side of the polarity reversal boundary. In the context of the Sun, chirality is an observable
signature of the handedness of the magnetic field of a solar feature. We concentrate on how to determine magnetic field direction
from chirality definitions and illustrate the technique in eight examples. The examples cover the spectrum of polarity boundaries
associated with filament channels and filaments ranging from those connected with active regions to those on the quiet Sun.
The applicability of the chiral method to all categories of filaments supports the view that active region filaments and quiescent
filaments are the extreme ends in a continuous spectrum of filaments.
The chiral method is almost universally applicable because many types of solar features that reveal chirality are now readily
seen in solar images accessible over the World Wide Web; also there are clear differences between left-handed and right-handed
solar structures that can be identified in both high- and low-resolution data although high-resolution images are almost always
preferable. In addition to filaments and filament channels, chirality is identifiable in coronal loop systems, flare loop
systems, sigmoids, some sunspots, and some erupting prominences. Features other than filament channels and filaments can be
used to resolve the 180-degree ambiguity because there is a one-to-one relationship between the chiralities of all features
associated with a given polarity reversal boundary.
Y. Lin is now at the Institute of Theoretical Astrophysics, University of Oslo. 相似文献
12.
For both even and odd-numbered solar cycles, right-hand heliform filaments predominate at middle and high latitudes in the northern hemisphere while left-handed ones predominate in the south. This recent discovery has prompted a re-examination of past measurements of magnetic fields in prominences. This re-examination indicates that Rust (1967), in his interpretation of solar cycle 20 measurements in terms of the Kippenhahn-Schlüter model, and Leroy, Bommier, and Sahal-Bréchot (1984), in their interpretation of solar cycle 21 measurements in terms of the Kuperus-Raadu model were both misled by the global pattern of helicity. While the original magnetic field measurements are consistent with the new results about heliform magnetic fields in filaments, neither of the well-known classes of two-dimensional models can produce both the proper axial field direction and the observed pattern of helicity. A global, subsurface velocity pattern that would twist the fields before emergence as filaments seems to be required. In this paper a twisted-flux-rope model consistent with the new understanding of filament fields is presented. The model is based on a constant- solution of the magnetostatic equations, where electric current densityj(r) =
B(r). The model filament has dimensions in general agreement with observations. It is shown to be stable if the length is less than 140 000 km to 1,400 000 km, depending on the value of. The model also provides a new explanation of eruptive prominences and for the origin of the entrained material. 相似文献
13.
This paper examines the locations where large, stable solar filaments form relative to magnetic bipoles lying underneath them.
The study extends the earlier work of F. Tang to include two additional classification categories for stable filaments and
to consider their population during four distinct phases of the solar cycle. With this new classification scheme, results
show that over 92% of filaments form in flux distributions that are nonbipolar in nature where the filament lies either fully
(79%) or partially (13%) above a polarity inversion line (PIL) external to any single bipole. Filaments that form within a
single bipole (traditionally called Type A) are not as common as previously thought. These results are a significant departure
from those of F. Tang. Consistency with the earlier work is shown when our data are regrouped to conform to the two-category
classification scheme for filaments adopted by F. Tang. We also demonstrate that only filaments that form along the external
PIL lying between two bipoles (62% of the full sample, traditionally called Type B) show any form of solar cycle dependence,
where their number significantly increases with magnetic activity over the solar cycle. Finally, current observations and
theoretical models for the formation of filaments are discussed in the context of the present results. We conclude that key
elements in the formation of the majority of filaments considered within this study must be the convergence of magnetic flux
resulting in either flux cancellation or coronal reconnection. 相似文献
14.
The relationships between disappearing solar filaments and geomagnetic activity are examined using data obtained between 1974 and 1980. The average level of geomagnetic activity is found to increase after the disappearance of large filaments. The magnitudes of the geomagnetic disturbances depend upon the sizes and, to a lesser extent, upon the darkness of the filaments. The delays between filament disappearances and resulting geomagnetic disturbances are typically 3–6 days, corresponding to Sun-Earth velocities 580–290 km s–1. These are consistent with the observed velocities of those coronal mass ejections that are associated with disappearing filaments.The average delay is: (a) shorter for large and dark filaments than for small and faint filaments respectively; (b) shorter during solar maximum than during solar minimum; (c) dependent in a complex way upon the longitudes of the filaments. Disturbances associated with filaments with longitudes 50 ° have delays 10 days.Quieter than average geomagnetic conditions sometimes occur for several days prior to the geomagnetic disturbances that follow disappearing filaments. 相似文献
15.
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
16.
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
17.
R. K. Zhigalkin G. V. Rudenko N. N. Stepanian V. G. Fainshtein N. I. Shtertser 《Bulletin of the Crimean Astrophysical Observatory》2008,104(1):67-78
Based on the developed method of jointly using data on the magnetic fields and brightness of filaments and coronal holes (CHs) at various heights in the solar atmosphere as well as on the velocities in the photosphere, we have obtained the following results: The upward motion of matter is typical of filament channels in the form of bright stripes that often surround the filaments when observed in the HeI 1083 nm line. The filament channels observed simultaneously in Hα and HeI 1083 nm differ in size, emission characteristics, and other parameters. We conclude that by simultaneously investigating the filament channels in two spectral ranges, we can make progress in understanding the physics of their formation and evolution. Most of the filaments observed in the HeI 1083 nm line consist of dark knots with different velocity distributions in them. A possible interpretation of these knots is offered. The height of the small-scale magnetic field distribution near the individual dark knots of filaments in the solar atmosphere varies between 3000 and 20000 km. The zero surface separating the large-scale magnetic field structures in the corona and calculated in the potential approximation changes the inclination to the solar surface with height and is displaced in one or two days. The observed formation of a filament in a CH was accompanied by a significant magnetic field variation in the CH region at heights from 0 to 30000 km up to the change of the predominant field sign over the entire CH area. We assume that this occurs at the stage of CH disappearance. 相似文献
18.
We have measured the rotation rate of short-lived solar filaments as a function of their latitude. The resulting rotation curve appears to be somewhat flatter than the corresponding curve for long-lived filaments. 相似文献
19.
F. Schmeidler 《Astronomische Nachrichten》1985,306(2):77-80
The agreement between radiastronomical measurements of the gravitational deflection of light at the solar limb and the theory of relativity is compatible with the exces found by most optical observers. The optical excess is caused by stars so near to the Sun that radioastronomical observations are impossible. Optical and radioastronomical measurements both make it likely that there is an additional term inversely proportional to a power higher than the first of the distance from the Sun. Results found by BOUET indicate that this additional term is of solar origin. 相似文献
20.
《New Astronomy》2003,8(6):529-536
Peculiarities in the characteristics of the solar differential rotation are investigated using hydrogen filaments as tracers. The existence of North–South (N–S) asymmetry in hydrogen filaments rotation is confirmed statistically. The connection of asymmetry with the solar activity cycles is established. It is found that the northern hemisphere rotates faster during the even cycles (Cycles 20 and 22) while the rotation of southern hemisphere dominates in odd one (Cycle 21). The mechanism of the solar activity should be responsible for the N–S asymmetry of the solar differential rotation. 相似文献