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1.
The full magnetic vector has been measured in both the photosphere and chromosphere across sunspots and plage in NOAA Active Region 8299. We investigate the vertical magnetic structure above the umbral, penumbral and plage regions using quantitative statistical comparisons of the photospheric and chromospheric magnetic data. The results include: (1) a general decrease in average magnetic flux density with height; (2) the direct detection of the superpenumbral canopy in the chromosphere; (3) values for dB/dz which are consistent with earlier investigations when derived from a straight difference between the two measurements, but which are somewhat small when derived from the B=0 condition, (4) a monolithic structure in the umbrae which extends well into the upper chromosphere, with a very complex and varied structure in penumbrae and plage, as evidenced by (5) a uniform magnetic scale height in the umbrae with an abrupt jump to widely varying scale heights in penumbral and plage regions. Further, we find (6) evidence that field extrapolations using the photospheric flux as the boundary may not agree with expectations or with observed coronal structures as well as those which use the chromospheric magnetic flux as the extrapolation starting point. 相似文献
2.
R. Muller 《Solar physics》1976,48(1):101-102
It is confirmed that the penumbral bright grains are moving towards the sunspots umbra. At the umbra-penumbra boundary their horizontal velocity is about 0.5 km s–1 and their displacement is inclined downwards with an angle of 5° to 20°. 相似文献
3.
Doppler spectroheliograms of sunspots and their surroundings have been obtained with a spatial resolution approaching one second of arc and a time resolution of 20 s per frame. Observations of 5 sunspots, located 18°, 45°, 56°, 60° and 72° from the disk center respectively, showed considerable long-lived fine structure and, in particular, indicated the following:
- The Evershed outflow terminated in spoke-like structures that constitute the ragged outer boundary of the penumbra. Some of these spokes extended more than 8000 km beyond the average outer boundary.
- Although there was considerable long-lived fine structure of both Doppler polarities in the extra-penumbral photosphere, the spatially-averaged horizontal flow was outward for roughly 10000 km beyond the outer boundary of the penumbra. This extra-penumbral velocity field was distinct from the Evershed flow, and, in particular, did not represent its extension beyond the end of the penumbral spokes.
4.
J. M. Beckers 《Solar physics》1968,3(2):258-268
Modifications to a Zeiss 1/4 Å filter are described which allow high spatial resolution observations of the line-of-sight velocities and magnetic fields in the photosphere and in sunspots. First results show: (1) the granular velocity field to be very strong; differences in upward motions in the granules and downward motions in between are as much as 6 km/sec; (2) the Evershed effect in sunspots to originate primarily in the dark regions between bright penumbral filaments. 相似文献
5.
N. R. Sheeley Jr. 《Solar physics》1972,25(1):98-103
During the summer and fall of 1971, Doppler spectroheliograms were obtained for several sunspots located near the solar limb. These observations confirm a previous result based on the study of only a few sunspots that in the plage-free photosphere surrounding sunspots the spatially-averaged, horizontal flow tends to be outward at 0.5–1.0 km s–1 for distances typically 10000–20000 km beyond the outer boundary of the penumbra. It is suggested that these material motions are the means by which small-scale fragments of magnetic flux are carried away from sunspots.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
6.
In this paper we present the results of a sunspot rotation study using Abastumani Astrophysical Observatory photoheliogram data for 324 sunspots. The rotation amplitudes vary in theinebreak 2–64° range (with maximum at 12–14°), and the periods around 0–20 days (with maximum atinebreak 4–6 days). It could be concluded that sunspot rotations are rather inhomogeneous and asymmetric, but several types of sunspots are distinguished by their rotational parameters.During solar activity maximum, sunspot average rotation periods and amplitudes slightly increase. This can be affected by the increase of sunspot magnetic flux tube depth. So we can suppose that sunspot formation during solar activity is connected to a rise of magnetic tubes from deeper layers of the solar photosphere, strengthening the processes within the tube and causing variations in rotation.There is a linear relation between tilt-angle oscillation periods and amplitudes, showing higher amplitudes for large periods. The variations of those periods and especially amplitudes have a periodical shape for all types of sunspots and correlate well with the solar activity maxima with a phase delay of about 1–2 years. 相似文献
7.
Ilgin Seker 《Solar physics》2013,286(2):303-314
We study whether the birthplaces of sunspots (defined as the location of first appearance in the photosphere) are related to the planetary tides on the Sun. The heliocentric longitudes of newly emerging sunspots are statistically compared to the longitudes of tidal peaks caused by the tidal planets Mercury, Venus, Earth, and Jupiter. The longitude differences between new sunspots and tidal planets (and their conjugate locations) as well as the magnitudes of the vertical and horizontal tidal forces at the birthplace of new sunspots are calculated. The statistical distributions are compared with simulation results calculated using a random sunspot distribution. The results suggest that the birthplaces of sunspots (in the photosphere) are independent of the positions of tidal planets and the strength of tidal forces caused by them. However, since the sunspots actually originate near the tachocline (well below the photosphere) and it takes considerable time for the disturbances to reach photosphere, we hesitate to conclude that the formation of sunspots are not related to planetary positions. 相似文献
8.
M. Sobotka 《Astronomische Nachrichten》2003,324(4):369-373
Sunspots and pores appear as a consequence of interactions between strong magnetic fields and moving plasma. A wide variety of small‐scale features, presumably of convective origin, are observed in photospheric layers of sunspots and pores: Umbral dots, light bridges, penumbral filaments, and penumbral grains. Each type of features has specific morphological, photometric, spectral, and kinematic characteristics. Spots and pores modify velocity fields in adjacent photosphere and sub‐photospheric layers. Recent high‐resolution spectral, broad‐band, and helioseismic observations of the structure, dynamics, and magnetic fields of sunspots and pores, together with theoretical interpretations, are discussed in this review. 相似文献
9.
Two novel methods of measuring umbral and penumbral areas of sunspots and of complex sunspot groups are described. Both methods comprise the digitization of photoheliograms by a frame grabber and the computation of intensity histograms of selected areas of activity. The first method, called cumulative histogram method, in principle determines the intensity boundaries umbra–penumbra and penumbra–photosphere from the intersections of linear fits into the corresponding parts of the cumulative histograms of sunspots. The second method, called maximum gradient method, marks image pixels of a given intensity level ±2 units wide as a white isophote on a display. Interactive variation of this level makes it easy to visually select the contour line fitting the boundary penumbra–photosphere (or umbra–penumbra) best. At the same level usually the width of the contour line is smallest. In both cases the summation of the pixel numbers above the corresponding intensity levels yields the umbral and the total sunspot areas, respectively. Some limitations of the two methods are discussed. 相似文献
10.
N. N. Morozhenko 《Solar physics》1978,60(1):47-56
Observations concerning the structure of sunspots, obtained during the fourth flight of the Soviet Stratospheric Observatory (SSO), are discussed. Objects brighter than the mean photospheric background inside the sunspot penumbra retaining the stable position sometimes vary within time intervals of a few minutes. The brightness change in pores can be explained by their different location at highest levels of the photosphere. The same mechanism can cause the brightness difference of the penumbra filaments. The gradient of the brightness variation inside the pores is determined. The value of this gradient was found to be practically the same for all dark objects. Most penumbral filaments show no magnetic expansion with growing distance from the spot center. 相似文献
11.
M. J. Hagyard 《Solar physics》1988,115(1):107-124
We have analyzed the vector magnetic field of an active region at a location of repeated flaring to determine the nature of the currents flowing in the areas where the flares initiated. The component of electric current density crossing the photosphere along the line-of-sight was derived from the observed transverse component of the magnetic field. The maximum concentrations of these currents occurred exactly at the sites of flare initiation and where the photospheric field was sheared the most. The calculated distribution of current density at the flare sites suggested that currents were flowing out of an area of positive magnetic polarity and across the magnetic inversion line into two areas of negative polarity. This interpretation was reinforced by a calculation of the source field, the magnetic field produced in the photosphere by the electric currents above the photosphere. In the vicinity of the flare sites, the calculated source field exhibited three particular characteristics: (1) maximum magnitudes at the sites of flare initiation, (2) a rotational direction where the vertical current density was concentrated, and (3) a fairly constant angular orientation with the magnetic inversion line. The source field was thus very similar to the field produced by two arcades of currents crossing the inversion line at the locations of greatest magnetic shear with orientations of about 60° to the inversion line. With this orientation, the inferred arcades would be aligned with the observed chromospheric fibrils seen in the H data so that the currents were field-aligned above the photosphere. The field thus exhibited a vertical gradient of magnetic shear with the shear decreasing upward from the photosphere. We estimated the currents in the two arcades by matching the source field derived from observations with that produced by a model of parallel loops of currents. We found that the loops of the model would each have a radius of 4500 km, a separation of 1830 km, and carry a current of 0.15 × 1012 A. Values of vertical current densities and source fields appearing in the umbrae of the two large sunspots away from the flare sites were shown to lie at or below the level of uncertainty in the data. The main source of this uncertainty lay in the method by which the 180° ambiguity in the azimuth of the transverse field is resolved in umbral areas. We thus concluded that these quantities in large umbrae should be treated with a healthy skepticism. Finally, we found that the source field at the flare sites was produced almost entirely by the angular difference between the observed and potential field and not by the difference in field intensity. 相似文献
12.
P. Maltby 《Solar physics》1972,26(1):76-82
Observations of the penumbral intensity of sunspots in 13 wavelength regions are presented. In 4 wavelength regions 54 sunspots are measured. In the other wavelength regions the number of sunspots considered ranges from 3–19.The penumbral intensity alters with position within the spot. This intensity variation is found to be comparable with the change in intensity from one spot to another. The penumbral intensity is found to be independent of spot size in the sample considered.The penumbra model of Kjeldseth Moe and Maltby (1969) with = 0.055 is supported by the measurements. 相似文献
13.
B. Ravindra 《Solar physics》2006,237(2):297-319
A time sequence of high-resolution SOHO/MDI magnetograms, Dopplergrams, and continuum images is used to study the moving magnetic
features (MMFs) in and out of penumbral filaments. Precursors of MMFs have been observed inside the penumbral filaments. One
hundred and fifteen out of 127 well-observed individual MMFs in the moat of two sunspots have been identified to have precursors
at an average distance of 4″ inside the penumbral filaments. The velocity of these precursors is small inside the penumbral
filaments and becomes large once the MMFs cross the outer penumbra. The paths followed by the MMFs exhibit large fluctuations
in their magnetic field strength values, with an additional hike in the fluctuations near the outer penumbra. It is also observed
that the path followed by the MMFs appear as a cluster of fibrils which could be traced back inside the penumbra. The appearance
of MMFs and their azimuthal velocity is position and time dependent.
Electronic Supplementary Material Electronic Supplementary Material is available for this article at 相似文献
14.
Mitsugu Makita 《Solar physics》1986,106(2):269-286
The broad-band circular polarization of sunspots is discussed on the basis of the observations made in the Okayama Astrophysical Observatory. The observation with the spectrograph proves that it is the integrated polarization of spectral lines in the observed spectral range. A velocity gradient in the line-of-sight can produce this integrated polarization due to the differential saturation between Zeeman components of magnetically sensitive lines. The observed degree of polarization and its spatial distribution in sunspots is explained when we introduce a differentially twisted magnetic field in addition to the velocity gradient. The differential twist has the azimuth rotation of the magnetic field along the line-of-sight and generates the circular polarization from the linear polarization due to the magneto-optical effect. The required azimuth rotation is reasonable and amounts at most to 30°. The required velocity gradient is compatible with the line asymmetry and its spatial distribution observed in sunspots. The observed polarity rule leads to the conclusion that the sunspot magnetic field has the differential twist with the right-handed azimuth rotation relative to the direction of the main magnetic field, without regard to the magnetic polarity and to the solar cycle. The twist itself is left-handed under the photosphere, when the sunspot is assumed to be a unwinding emerging magnetic field. 相似文献
15.
One goal of helioseismology is to determine the subsurface structure of sunspots. In order to do so, it is important to understand
first the near-surface effects of sunspots on solar waves, which are dominant. Here we construct simplified, cylindrically-symmetric
sunspot models that are designed to capture the magnetic and thermodynamics effects coming from about 500 km below the quiet-Sun
τ
5000=1 level to the lower chromosphere. We use a combination of existing semi-empirical models of sunspot thermodynamic structure
(density, temperature, pressure): the umbral model of Maltby et al. (1986, Astrophys. J. 306, 284) and the penumbral model of Ding and Fang (1989, Astron. Astrophys. 225, 204). The OPAL equation-of-state tables are used to derive the sound-speed profile. We smoothly merge the near-surface properties
to the quiet-Sun values about 1 Mm below the surface. The umbral and penumbral radii are free parameters. The magnetic field
is added to the thermodynamic structure, without requiring magnetostatic equilibrium. The vertical component of the magnetic
field is assumed to have a Gaussian horizontal profile, with a maximum surface field strength fixed by surface observations.
The full magnetic-field vector is solenoidal and determined by the on-axis vertical field, which, at the surface, is chosen
such that the field inclination is 45° at the umbral – penumbral boundary. We construct a particular sunspot model based on
SOHO/MDI observations of the sunspot in active region NOAA 9787. The helioseismic signature of the model sunspot is studied
using numerical simulations of the propagation of f, p
1, and p
2 wave packets. These simulations are compared against cross-covariances of the observed wave field. We find that the sunspot
model gives a helioseismic signature that is similar to the observations. 相似文献
16.
Broad band pinhole photometer intensity observations of 15 large sunspots covering the spectral region 0.387–2.35 m are presented. The data are based on measurements on approximately 500 days during the period June, 1967 to December, 1979.We have found real and significant intensity differences between large sunspots. These differences may be explained by a systematic variation in the umbral temperature throughout the solar cycle. A connection between umbra intensity and heliographic latitude is discussed.No center-limb variation in the umbra/photosphere intensity ratio is detected. We have searched for possible connections between umbra intensity and a number of other sunspot parameters, like the spot size, without detecting any significant correlation. We conclude that the umbra/photosphere intensity ratio seems to be a unique function of epoch for large sunspots. 相似文献
17.
E. Haugen 《Solar physics》1969,9(1):88-101
The wavelength shifts of approximately 8000 absorption elements in the H-line from spectra of 66 different sunspot regions have been measured.The average velocity field in the chromosphere close to sunspots is determined. Inside 15000 km from the spot's penumbral rim the average velocity vector is directed towards the spot and downwards in the chromosphere; the angle with the horizontal direction is on the average equal to 20°. The magnitude of the average velocity vector shows a maximum of 6.8 ± 1.2 km/sec just outside the penumbral rim and decreases quickly with increasing distance from the spot. Outside 15000 km from the penumbral rim the average velocity vector is small (-0.7 km/sec) and directed nearly vertically outwards from the sun. No significant tangential component of the average velocity field is found.The deviations of the individual elements from the average velocity field are on the average larger than the value of the average velocity. The total rms deviation in the line of sight velocity is equal to 6.8 km/sec. Thus, a large number of elements, as used in this investigation, is required to give significant values of the average velocity vector.We have also observed velocities in the penumbra. The average velocity vector is here probably small and its direction uncertain. The rms deviation in the line of sight velocities observed in the penumbra is equal to 7.5 km/sec. 相似文献
18.
Béla Kálmán 《Solar physics》2002,209(1):109-117
Comparison of photographic observations and vector-magnetograph measurements demonstrate that the outer boundary of the sunspot
penumbra – even in complex sunspot groups – closely follows the 0.075 T iso-gauss line of the total value of the magnetic
field, corresponding approximately to the equipartition value in the photosphere. Radio observations also show this feature.
The thick penumbra model with interchange convection (Jahn and Schmidt, 1994) gives the best explanation of the penumbral
structure.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1020985530075 相似文献
19.
H. I. Abdussamatov 《Solar physics》1976,48(1):117-119
From investigating spectrograms of penumbrae of some sunspots it is concluded that the maximum magnetic field strength occurs in dark filaments and amounts to 1800–1900 G; the intensity of the magnetic field in dark filaments is 100–400 G larger than in the neighbouring bright filaments; the bright filaments seen in the space between the dark features cannot be attributed to the ordinary undisturbed photosphere. 相似文献
20.
The uncertainty about a possible correlation between magnetic field strength, inclination, and the continuum intensity of sunspot penumbral fine-structure has been removed from detailed analysis of a spatially very well-resolved spectrum: the darker, long penumbral lanes host a 10% stronger and 30° flatter magnetic field as compared to the field in bright penumbral locations. This finding is not only based on the high spatial resolution but also on the use of a spectral line, here Fe 6842.7 Å, obtaining its essential contribution from those deep layers where the penumbral structure is seen, i.e. the continuum intensity level. The almost perfect correlation establishes that the penumbral structure is formed by the two magnetic components mainly differing by the field inclination. The different results from other Zeeman lines, as, e.g., Fe 6302.5 Å, indicate a different field structure above the white-light penumbral layers. 相似文献