共查询到20条相似文献，搜索用时 383 毫秒
1.
V. A. Perebeinos N. N. Stepanian V. G. Fainshtein G. V. Rudenko 《Bulletin of the Crimean Astrophysical Observatory》2011,107(1):43-50
Height variation of the magnetic field structure over groups of sunspots for heights ranging from the photosphere to the source
surface (R = 2.5 Ro, where Ro is the radius of the Sun) is examined. For all heights, starting from the photospheric level, groups of
sunspot are shown as being independent of long-lived boundaries of large-scale structures rotating with a period shorter than
the Carrington period. At heights of 1–1.5 Ro, there is a clear relation between sunspot groups and boundaries separating
the head and tail sunspots in the groups (the Hale boundaries). The rotation periods of these structures are close to the
Carrington period, their lifespan being less than three to five rotations. The maximal intensity of the solar magnetic field
drops by two orders when height increases from H = 1 to H = 1.1 Ro. Further decrease in intensity proceeds gradually (dropping by one order from H = 1.1 to 2.5 Ro). The results obtained can be considered as evidence that large-scale magnetic field structures and long-lived
boundries between them (the lines dividing polarities of the magnetic field or zero lines) all exist irrespective of sunspot
fields being generated by other sources than sunspots. At the photospheric level, active regions fields are superimposed on
these structures. 相似文献
2.
N. N. Stepanyan Z. S. Akhtemov V. G. Fainstein G. V. Rudenko 《Bulletin of the Crimean Astrophysical Observatory》2013,109(1):115-123
The radial component of the solar magnetic field, Br, was calculated in the potential approximation in the height range from 1 to 2.5 solar radii, Ro. According to these data, synoptic maps of the magnetic field for solar cycles 21–23 were constructed. For each 10-degree latitudinal zone, the proportion of its area, S +field, that was occupied by the “+” field in each rotation was found. In the entire latitudinal zone, the radial component of the field is assumed to be positive if S+field ≥ 80% and negative if S +field ≤ 20%. The field proved to be virtually unipolar at the level of the photosphere (R = Ro) during most of the cycle, from the poles to the north and south latitude ≈60°. In the vicinity of minimums between cycles 21 and 22, as well as cycles 22 and 23, for a few rotations of the Sun, the field was almost unipolar within the range of latitudes (?40°)-90°. At R = 2.5 Ro, for most of each cycle, the field was unipolar in the range of latitudes (?20°-(-90°)) and (20°–90°). According to our interpretation, the shift of the polar-field boundary to the equator with height reflects superradial expansion of open magnetic flux tubes from the polar coronal holes. It was found that the reversal of the polar fields began with 1–2 rotations and ended from 2 to 14 solar rotations earlier at great heights than at the surface of the Sun. This indicates that the reversal of the large-scale field occurs first and then that of the small-scale one. In the study of the sectoral structure of the magnetic field at different heights it was found that the boundaries that rotate with a period of less than the Carrington revolution extend to greater heights than the boundaries with a Carrington or longer period. We assume that the boundaries of the first type are formed by the large-scale structures of the magnetic field and the boundaries of the second type are determined by the active regions. 相似文献
3.
High-resolution mosaics of the solar polar magnetic fields have been constructed using individual magnetograms obtained with the video magnetograph of the Big Bear Solar Observatory, and the properties of these mosaics are demonstrated in this paper. The mosaics show selected regions of the polar fields on several days during the rising phase of Cycle 23, and are related to the global polar fields (i) by superposing the mosaic for a given day on to a full-disk SOHO-MDI magnetogram obtained on the same day, (ii) by plotting the mosaics in polar projection and using these to identify the approximate regions reported by the mosaics on the NSOKP polar synoptic plots, and (iii) by imposing the locations of the H filaments on to the mosaics in order to infer the neutral lines of the large-scale fields. We have studied the fine structure of the large-scale unipolar fields near the poles and, in particular, have constructed histograms of the magnetic field intensities within particular regions of the mosaics and, in this way, have estimated the ratios of the number of magnetic knots of opposite polarities within the unipolar plumes. We have also generated enlargements of the polar regions of the NSOKP daily magnetograms. These and statistical studies have shown that on days for which the BBSO mosaics are not available, the NSOKP enlargements may be used to study the high-resolution polar fields. Time-series of mosaics obtained over four-hour periods on September 6 and November 18 show that considerable evolution in the structure of existing flux knots and the formation of several new knots has taken place during these periods. 相似文献
4.
In this paper we utilize the latitude distribution of the coronal temperature during the period 1984–1992 that was derived in a paper by Guhathakurta et al, 1993, utilizing ground-based intensity observations of the green (5303 Fe XIV) and red (6374 Fe X) coronal forbidden lines from the National Solar Observatory at Sacramento Peak, and estabish its association with the global magnetic field and the density distributions in the corona. A determination of plasma temperature,T, was estimated from the intensity ratio Fe X/Fe XIV (whereT is inversely proportional to the ratio), since both emission lines come from ionized states of Fe, and the ratio is only weakly dependent on density. We observe that there is a large-scale organization of the inferred coronal temperature distribution that is associated with the large-scale, weak magnetic field structures and bright coronal features; this organization tends to persist through most of the magnetic activity cycle. These high-temperature structures exhibit time-space characteristics which are similar to those of the polar crown filaments. This distribution differs in spatial and temporal characterization from the traditional picture of sunspot and active region evolution over the range of the sunspot cycle, which are manifestations of the small-scale, strong magnetic field regions.affiliated to USRA 相似文献
5.
E. E. Benevolenskaya 《Solar physics》1996,167(1-2):47-55
The polar magnetic field on the Sun changes its sign during the maximum of solar cycles. It is known that the phenomenon of three-fold reversal of the polar magnetic field occurred in solar cycle 20. Using the magnetograph data of the Mount Wilson Observatory from 1967 to 1993, we confirm a previously suggested topological model of the three-fold magnetic-field reversal (Benevolenskaya, 1991). From the data set we have found that cycles with three-fold polar magnetic field reversals are characterized by a pronounced high-frequency component of the magnetic field compared with cycles with single polar magnetic-field reversals. 相似文献
6.
In this paper we present our results of the application of the magnetograph formula to synthetic Stokes V profiles in prominences. We investigate both the Zeeman and atomic-polarization signatures within the V profile and question why previous attempts to determine magnetic field strength, on average, were correct, even if the magnetograph formula does not apply in general.The National Center for Atmospheric Research is sponsored by the National Science FoundationSponsored by the Summer Undergraduate Program of the High Altitude Observatory 相似文献
7.
NOAA active region 6659, during its June 1991 transit across the solar disk, showed highly sheared vector magnetic field structures
and produced numerous powerful flares, including five white-light flares. Photospheric vector magnetograms of this active
region were obtained at the Huairou Solar Observing Station of the Beijing Astronomical Observatory. After the resolution
of the 180° ambiguity of the transverse magnetic field and transformation of off-center vector magnetograms to the heliographic
plane, we have determined the photospheric vertical current density and discussed the relationship with powerful flares. The
following results were obtained: (a) The powerful 3B/X12 flare on June 9, 1991 was triggered by the interaction between the
large-scale electric current system and magnetic flux of opposite polarity. (b) The kernels of the powerful Hβ flare (sites of the white-light flare) were close to the peaks of the vertical electric current density. (c) Some small-scale
structures of the vertical current relative to the magnetic islands of opposite polarity have not been found. This probably
implies that the electric current is not always parallel to the magnetic field in solar active regions. 相似文献
8.
High-resolution magnetograph observations of the polar magnetic fields have been obtained at intervals of time since the end of 1986 at Big Bear Solar Observatory. The Big Bear data differ from the low-resolution, full-disk magnetograph observations in that the 2 arc sec resolution makes it possible to resolve concentrated field upward of 100 G. The purpose of this ongoing observation is to examine the evolution of polar fields during the expected polarity reversal as cycle 22 passes its maximum phase, and secondly, to study the polar magnetic field: its true field strength, distribution, and how it compares to other parts of the quiet Sun.We find that the >70° net polar flux of both poles has not reversed as of the end of 1989. However, in the lower latitudes of both poles, 50° to 70°, there are signs reminiscent of those preceding the reversals in cycles 19 and 20. These include: decreasing field intensity in the old polarity fluctuations in net flux between the old and new polarities.We find that the net average longitudinal polar fields (above 50°) are 1–2 G, in agreement with results found in cycles 19 and 20. For individual elements, however, the strongest observed field strength poleward of 70° is over 100 G.We compare the polar fields with the equatorial limb as a function of latitute and longitude, respectively, and find the polar fields are comparable to (or stronger than) the quiet equatorial limb. When the observed mean flux density of the polar field as a function of latitude is corrected for limb-darkening and projection effects (assuming the field is radial), the result is nearly constant. These results suggest that despite the high latitudes, the polar fields have field strength and distribution similar to other parts of the quiet Sun. 相似文献
9.
Z. S. Akhtemov O. A. Andreeva G. V. Rudenko N. N. Stepanian V. G. Fainstein 《Bulletin of the Crimean Astrophysical Observatory》2014,110(1):114-124
Calculations of the magnetic field in the potential approximation (using Bd technology (Rudenko, 2001)) were used to study the time variations of several parameters of the large-scale magnetic field in the solar atmosphere during the last four cycles. Synoptic maps (SMs) for the radial component Br of the calculated magnetic field were plotted at 10 heights between the solar surface (R = R ⊙) and the source (R = 2.5R ⊙). On these SMs, we marked the 10-degree latitudinal areas. The following (averaged within the zone) characteristics of the magnetic field were determined corresponding to these zones: Sp, Sm; S +fields , where Sp is the positive value of Br, Sm is the averaged modulus of the negative Br; S +fields is the percentage of latitudinal zones with positive Br. The analysis of temporal variations in the magnitude of S points to different origins of the large-scale magnetic field in the near-equatorial and polar regions of the solar atmosphere. The analysis of temporal variations of S +fields showed that there were almost no periods with a mixed polarity at R = 2.5R ⊙ during the 21st and 22nd solar cycles and in an ascending phase of the 23rd cycle. However, beginning from the maximum of the 23rd cycle, a mixed polarity in the equatorial region was observed until the end of the long minimum of activity. We hypothesized that this could be a precursor for a long minimum between the 23rd and 24th solar cycles. It was shown that during the maximum phase of the 24th solar cycle the magnetic field at R = R ⊙ is much less than that during the maximum phase of the 23rd cycle, and in the region from 55° to 75°, this difference reaches an order of magnitude. 相似文献
10.
We describe the application of the synoptic transport equation to simulate the temporal evolution of the magnetic flux over
the solar surface. This provides a means of predicting each day both the synoptic maps for the Carrington rotation starting
the next day and the instantaneous map of the solar flux over the whole solar surface for the next day. The reliability of
the predicted synoptic maps is tested by comparing the locations of the zero-flux contour with those of the observed maps
produced by the National Solar Observatory, Kitt Peak and with the locations of Hα filaments measured on filtergrams obtained
by the Big Bear Solar Observatory. We conclude that the best match at high latitudes is obtained by long-term simulations
(over 20 rotations) with flux updates each rotation between latitudes ± 60°. We illustrate the use of the simulations to describe
the evolution of the polar fields at the time of the polarity reversals in Cycle 23. The reconstruction of the instantaneous
maps is tested by comparison with full-disk magnetograms. The method provides a simple means of estimating the large-scale
flux distribution over the whole surface. It does not take account of flux emerging after the central meridian passage each
rotation so it is only approximate in the activity belts but provides a reliable map beyond those latitudes. 相似文献
11.
Recent dedicated Hinode polar region campaigns revealed the presence of concentrated kilogauss patches of the magnetic field in the polar regions of the Sun, which are also shown to be correlated with facular bright points at the photospheric level. In this work, we demonstrate that this spatial intermittency of the magnetic field persists even up to the chromospheric heights. The small-scale bright elements visible in the bright network lanes of the solar network structure as seen in the Ca ii H images are termed network bright points. We use special Hinode campaigns devoted to the observation of polar regions of the Sun to study the polar network bright points during the phase of the last extended solar minimum. We use Ca ii H images of chromosphere observed by the Solar Optical Telescope. For magnetic field information, level-2 data of the spectro-polarimeter is used. We observe a considerable association between the polar network bright points and magnetic field concentrations. The intensity of such bright points is found to be correlated well with the photospheric magnetic field strength underneath with a linear relation existing between them.
相似文献12.
Extreme-ultraviolet data from EIT/SOHO (1996–2002), soft X-ray data from Yohkoh (1991–2001), and magnetic field data from MDI/SOHO (1996–2002) and Kitt Peak Observatory, NSO/NOAO (1991–2002) are analyzed
together in the form of synoptic maps for the investigation of solar cycle variations of the corona and their relation to
the magnetic field. These results show new interesting relations between the evolution of the topological structure of the
corona, coronal heating and the large-scale magnetic field. The long-lived coronal structures are related to complexes of
solar activity and display quasi-periodic behavior (in the form of impulses of coronal activity) with periods of 1.0–1.5 year,
in the axisymmetric distribution of EUV and X-ray fluxes during the current solar cycle 23. In particular, during the second
maximum of this cycle the solar corona became somewhat hotter than it was in the period of the first maximum. 相似文献
13.
E. E. Benevolenskaya 《Solar physics》1995,161(1):1-8
The source of the poloidal magnetic field was fixed using a uniform series of surface low-resolution magnetic field observations begun at Wilcox Solar Observatory at Stanford. The results obtained confirm the idea that low-frequency dynamo waves with a period approximately equal to 22 years and a high-frequency wave of a quasi-two-year period can coexist. It seems that an interaction between these components in the convection zone takes place on the Sun. Surface large-scale solar magnetic fields are analyzed using a two-dimensional Fourier method technique to study the poloidal field distribution. The first harmonic approximately equals the period of the magnetic cycle, appears at all latitudes, and reaches its the maximum value in the polar regions. Moreover, spectral analyses of axisymmetric magnetic field derivative in time found that the second important harmonic of a period approximately equal to two years appears at all latitudes. This second high-frequency harmonic dominates the polar latitude regions at the same time as the low-frequency one. 相似文献
14.
We compare the shape and position of some plasma formations visible in the polar corona with the cyclic evolution of the global
magnetic field. The first type of object is polar crown prominences. A two-fold decrease of the height of polar crown prominences
was found during their poleward migration from the middle latitudes to the poles before a polar magnetic field reversal. The
effect could be assigned to a decrease of the magnetic field scale. The second type of object is the polar plumes, ray like
structures that follow magnetic field lines. Tangents to polar ray structures are usually crossed near some point, “a magnetic
focus,” below the surface. The distance q between the focus and the center of the solar disk changes from the maximum value about 0.65 R
⊙ at solar minimum activity to the minimum value about 0.45 R
⊙ at solar maximum. At first glance this behaviour seems to be contrary to the dynamics of spherical harmonics of the global
magnetic field throughout a cycle. We believe that the problem could be resolved if one takes into account not only scale
changes in the global magnetic field but also the phase difference in the cyclic variations of large-scale and small-scale
components of the global field. 相似文献
15.
Models of the polarity reversals of the Sun's polar magnetic fields based on the surface transport of flux are discussed and are tested using observations of the polar fields during Cycle 23 obtained by the National Solar Observatory at Kitt Peak. We have extended earlier measurements of the net radial flux polewards of ±60° and confirm that, despite fluctuations of 20%, there is a steady decline in the old polarity polar flux which begins shortly after sunspot minimum (although not at the same time in each hemisphere), crosses the zero level near sunspot maximum, and increases, with reversed polarity during the remainder of the cycle. We have also measured the net transport of the radial field by both meridional flow and diffusion across several latitude zones at various phases of the Cycle. We can confirm that there was a net transport of leader flux across the solar equator during Cycle 23 and have used statistical tests to show that it began during the rising phase of this cycle rather than after sunspot maximum. This may explain the early decrease of the mean polar flux after sunspot minimum. We also found an outward flow of net flux across latitudes ±60° which is consistent with the onset of the decline of the old polarity flux. Thus the polar polarity reversals during Cycle 23 are not inconsistent with the surface flux-transport models but the large empirical values required for the magnetic diffusivity require further investigation. 相似文献
16.
High resolution KPNO magnetograph measurements of the line-of-sight component of the photospheric magnetic field over the entire dynamic range from 0 to 4000 gauss are used as the basic data for a new analysis of the photospheric and coronal magnetic field distributions. The daily magnetograph measurements collected over a solar rotation are averaged onto a 180 × 360 synoptic grid of equal-area elements. With the assumption that there are no electric currents above the photospheric level of measurement, a unique solution is determined for the global solar magnetic field. Because the solution is in terms of an expansion in spherical harmonics to principal index n = 90, the global photospheric magnetic energy distribution can be analyzed in terms of contributions of different scale-size and geometric pattern. This latter procedure is of value (1) in guiding solar dynamo theories, (2) in monitoring the persistence of the photospheric field pattern and its components, (3) in comparing synoptic magnetic data of different observatories, and (4) in estimating data quality. Different types of maps for the coronal magnetic field are constructed (1) to show the strong field at different resolutions, (2) to trace the field lines which open into interplanetary space and to locate their photospheric origins, and (3) to map in detail coronal regions above (specified) limited photospheric areas.The National Center for Atmospheric Research is sponsored by the National Science foundation.Kitt Peak National Observatory is operated by the Association of Universities for Research in Astronomy, Inc. Under contract with the National Science Foundation. 相似文献
17.
It is shown that leading and following magnetic field lines are inclined toward each other by a few degrees at nearly all latitudes in both the north and south hemispheres. The amplitudes of these inclinations are lower by about a factor 3 for weak fields than for strong fields. There are significant differences between the hemispheres and from one activity cycle to the next in the leading and following polarity field-line inclinations at latitudes poleward of the activity latitudes. In a narrow latitude zone just south of the solar equator the inclinations of both the leading and following fields reduce to zero (or perhaps slightly negative values). Although one would expect such a zone at the equator, where diffusion will mix field lines with opposite inclinations from the two hemispheres, it is not clear why this zone should be on one side of the equator only. The results discussed here were obtained with Mount Wilson magnetograph data (1967–1992), and are confirmed in many respects with National Solar Observatory/Kitt Peak (NSO/KP) data (1976–1986).Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation. 相似文献
18.
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
19.
Robert C. Smithson 《Solar physics》1975,40(1):241-246
A new magnetograph using a solid state monolithic linear silicon diode array has been constructed at Lockheed Solar Observatory. This magnetograph uses a digital image processor, and makes data available both in digital and analog form. The diode array detector is capable of a signal-to-noise ratio of 2000:1 or better when cooled to a temperature of -40 deg centigrade. Thus, intensity differences of the order of one part in a thousand may easily be detected without signal averaging. This instrument may be considered a prototype for an instrument using a two-dimensional array. The magnetograph is now fully operational, and is being used to produce data for statistical studies of solar magnetic field diffusion. 相似文献
20.
A magnetograph is an instrument which makes measurement of solar magnetic field by measuring Zeeman induced polarization in
solar spectral lines. In a typical filter based magnetograph there are three main modules namely, polarimeter, narrow-band
spectrometer (filter), and imager(CCD camera). For a successful operation of magnetograph it is essential that these modules
work in synchronization with each other. Here, we describe the design of instrument control system implemented for the Solar
Vector Magnetograph under development at Udaipur Solar Observatory. The control software is written in Visual Basic and exploits
the Component Object Model (COM) components for a fast and flexible application development. The user can interact with the
instrument modules through a Graphical User Interface (GUI) and can program the sequence of magnetograph operations. The integration
of Interactive Data Language (IDL) ActiveX components in the interface provides a powerful tool for online visualization,
analysis and processing of images. 相似文献