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1.
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
2.
We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space Flight Center (MSFC) (FeI 5250.2 Å) and SOHO/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic field distribution of active and quiet regions considered as global structures. To study the spatial structure of sunspots, we use a well-known method of determining the fractal dimension based on an analysis of the perimeter—area relation. To analyze the fractal properties of the spatial magnetic field distribution over the solar surface, we use a technique developed by Higuchi. We have revealed the existence of three families of self-similar contours corresponding to the sunspot umbra, penumbra, and adjacent photosphere. The fractal coefficient has maxima near the umbra—penumbra and penumbra—photosphere boundaries. The fractal dependences of the longitudinal and transverse magnetic field distributions are similar, but the fractal numbers themselves for the transverse fields are larger than those for the longitudinal fields approximately by a factor of 1.5. The fractal numbers decrease with increasing mean magnetic field strength, implying that the magnetic field distribution is more regular in active regions. 相似文献
3.
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
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.
K. Puschmann B. Ruiz Cobo M. Vzquez J.A. Bonet A. Hanslmeier 《Astronomische Nachrichten》2003,324(4):352-353
From inversion of a time series of slit spectra, observed in a quiet region of the solar photosphere, averaged models of a granular cell have been obtained showing the stratification of physical quantities versus optical depth and geometrical height. Furthermore a semi‐empiric dynamic model of a mean granular cell has been derived and the results are presented. 相似文献
6.
The differences between physical conditions in solar faculae and those in sunspots and quiet photosphere (increased temperature and different magnetic field topology) suggest that oscillation characteristics in facula areas may also have different properties. The analysis of 28 time series of simultaneous spectropolarimetric observations in facula photosphere (Fe?i 6569 Å, 8538 Å) and chromosphere (Hα, Ca?ii 8542 Å) yields the following results. The amplitude of five-minute oscillations of line-of-sight (LOS) velocity decreases by 20?–?40% in facula photosphere. There are only some cases revealing the inverse effect. The amplitude of four- to five-minute LOS velocity oscillations increases significantly in the chromosphere above faculae, and power spectra fairly often show pronounced peaks in a frequency range of 1.3?–?2.5 mHz. Evidence of propagating oscillations can be seen from space?–?time diagrams. We have found oscillations of the longitudinal magnetic field (1.5?–?2 mHz and 5.2 mHz) inside faculae. 相似文献
7.
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
8.
Martin D. Altschuler 《Solar physics》1967,1(3-4):377-388
Recently E. H. Schroeter showed that the electrical conductivity of the sunspot umbra, at least in the upper photospheric layers, is about ten-thousand times less than the value used by Cowling. This result implies that electrical conductivity gradients near sunspots may be relatively large. Upon taking such gradients into consideration, we find that the photosphere is current free and that current rings might encircle the sunspot, under suitable conditions, both in the lower photosphere and in the chromosphere. Plasma motions are neglected in the calculation. 相似文献
9.
Phase-correlation statistics comparing acoustic radiation coming out of a particular point on the solar photosphere with acoustic radiation going into it show considerably reduced sound travel times through the subphotospheres of active regions. We have now applied techniques in phase-sensitive seismic holography to data from the Solar Oscillations Investigation – Michelson Doppler Imager (SOI-MDI) on the Solar and Heliospheric Observatory (SOHO) spacecraft to obtain high resolution phase-correlation maps of a large, complex active region and the `acoustic moat' which surrounds it. We report the following new results: First, the reduced sound travel-time perturbations in sunspots, acoustic moats, and isolated plages increase approximately in proportion to the logarithm of the surface magnetic flux density, for flux densities above 10 G. This is consistent with an interpretation of the travel-time anomalies, observed with holographic and other local-helioseismic procedures, as caused by acoustic Wilson-like depressions in photospheres of magnetic regions. Second, we find that, compared with isolated plages, the acoustic moats have an additional sound travel-time reduction on the order of 3–5 s which may be explained by a thermal excess due to the blockage of convective transport by the sunspot photosphere. Third, the combined effect of the Wilson depression in plages, acoustic moats, and sunspots may explain the observed variation of global p-mode frequencies with the solar cycle. Fourth, we find that active regions, including sunspots, acoustic moats, and plages, significantly reflect p modes above the acoustic cut-off frequency, where the surface of the quiet Sun acts as a nearly perfect absorber of incident acoustic radiation. 相似文献
10.
C. S. Rosenthal 《Solar physics》1992,139(1):25-45
Observations of the scattering of acoustic waves by sunspots show a substantial deficit in scattered power relative to incident power. A number of calculations have attempted to model this process in terms of absorption at the magnetohydrodynamic Alfvén resonance. The results presented here extend these calculations to the case of a highly structured axisymmetric translationally invariant flux-tube embedded in a uniform atmosphere. The fractional energy absorbed is calculated for models corresponding to flux-tubes of varying radius, mean flux-density and location below the photosphere. The effects of twist are also included.It is found that absorption can be very efficient even in models with low mean magnetic flux density, provided the flux is concentrated into intense slender annuli. Twist is found to increase the range of wave numbers over which absorption is efficient, but it does not remove the low absorption at low azimuthal orders which is a feature of resonance absorption calculations in axisymmetric geometry, and which is in conflict with observation.These results suggest that resonance absorption could be an efficient mechanism in plage fields and fibril sunspots as well as in monolithic sunspots. At present it is too early to make any definite deductions about sunspot structure from the observations, but the possible future use of sunspot seismology to resolve open questions in the theory of sunspots is briefly discussed. 相似文献
11.
An analysis of the local sources (LS) structure of the S-component of solar radio emission confirms the presence of a core component which is characterized by strong circular polarization and a steep growing spectrum at shorter centimeter wavelengths. These details coincide in position with the sunspots' umbra and their height above the photosphere does not generally exceed about 2000 km. Gyroresonance emission of thermal electrons of the corona is generally accepted as being responsible for this type of emission. The spectral and polarization observations of LS made with RATAN-600 using high resolution in the wavelength range 2.0–4.0 cm, allow us to measure the maximum magnetic fields of the corresponding sunspots at the height of the chromosphere-corona transition region (CCTR). This method is based on determining the short wavelength limit of gyroresonance emission of the LS and relating it to the third harmonic of gyrofrequency.An analysis of a large number of sunspots and their LS (core component) has shown a good correlation between radio magnetic fields near the CCTR and optical photospheric ones. The magnetic field in CCTR above a sunspot is found only 10 to 20% lower than in the photosphere. The resulting gradient of the field strength is not less than 0.25 G km–1. This result seems to contradict the lower values of magnetic fields generally found above sunspots using the chromospheric H line. Some possible ways of overcoming this difficulty are proposed. 相似文献
12.
Syun-Ichi Akasofu 《Planetary and Space Science》1984,32(10):1257-1261
It is suggested that the formation of a pair of sunspots results from amplification of the weak, largescale fields in the photosphere, rather than from emergence of a hypothetical magnetic flux “tube” from beneath the photosphere. 相似文献
13.
R. Muller 《Solar physics》1983,85(1):113-121
A high resolution time series of pictures, obtained at Pic du Midi Observatory, is used to analyze the dynamical behavior of facular points in the quiet Sun. The following characteristics of the behavior are revealed: (a) relative to the supergranular pattern, facular points appear at the supergranular boundaries, rarely inside the cells; (b) relative to the pattern of the granulation, they appear in spaces at the junction of several granules, never inside a granule nor in a space between two granules only; (c) their mean lifetime is 18 min; (d) they remain in intergranular lanes during their whole life; (e) their observed size never significantly exceeds 0″. 5; (f) they have a strong tendency to appear very close to an already existing facular point; (g) about 15% of them seem to split in two facular points; (h) they disappear simply by fading away in an intergranular space; (i) they never merge with another facular point or with a granule. The formation of facular points in the quiet photosphere is very closely connected to both granular and supergranular patterns. Some possible consequences on the behavior of the associated magnetic flux tubes are discussed. 相似文献
14.
Observations have consistently pointed out that the longitudinal and latitudinal motions of sunspots are correlated. The magnitude of the covariance was found to increase with latitude, and its sign was found to be positive in the N-hemisphere and negative in the S-hemisphere. This correlation was believed to be due to the underlying turbulence where the sunspot flux tubes are anchored, and the covariance had the right sign and magnitude needed to explain the transfer of angular momentum toward the equator through Reynolds stresses.Here we present an alternate explanation for these sunspot velocity correlations: It is believed that the dynamo operates in a thin overshoot layer beneath the base of the convection zone, and the flux tubes generated there produce sunspots at the photosphere. By studying the dynamics of flux tubes emerging from the base of the convection zone to the photosphere, we show that these velocity correlations of sunspots could be merely a consequence of the effect of Coriolis force on rising flux tubes. The effect of the Coriolis force, as demonstrated by even a back-of-the-envelope calculation, is to push the faster rotating spots equatorward and the slower rotating spots poleward, giving rise to a correlation in their longitudinal and latitudinal velocities, which is positive in the N-hemisphere and negative in the S-hemisphere. The increase in the correlation with latitude is due to the increase in magnitude of the Coriolis force. Hence we show that these velocity correlations might have nothing to do with the Reynolds stresses of the underlying turbulence.We present analyses of observations, and show that the covariances of plages are an order of magnitude higher than the sunspot covariances. If plages and sunspots share the same origin, and if their horizontal velocity correlations are wholly due to the effect of Coriolis force on rising flux tubes, then the study of their dynamics suggests that the flux tubes that form plages should have diameters of a couple of thousand km at the base of the convection zone and remain intact until they reach the photosphere, whereas sunspots should be formed by a collection of small flux tubes (each measuring about a hundred km in diameter), that rise through the convection zone as individual elements and coalesce when they emerge through the photosphere.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation. 相似文献
15.
Nobuyuki Oda 《Solar physics》1984,93(2):243-255
Time-sequential high quality photographs of the photospheric granule on a quiet region of the disc center obtained at the Pic-du-Midi Observatory by Kawaguchi are analyzed. The size variation of individual granules in the area of 54×52 on the photosphere are traced over a period of 4 min. The granules are classified according to their morphological features as follows. (1) Active granules, they repeat the expansion and the fragmentation. (2) Quiet granules, they do not alter the size noticeably during the observed time span. (3) Declining granules, they disappear without further fragmentation or merging.The distribution of active granules on the photosphere reveals a presence of a cellular pattern. The relationships between the cellular pattern and the brightness on the quiet photosphere are investigated. The results show that there is a good spatial correlation between them. The autocorrelation analysis shows a kind of periodicity on the photospheric intensity and its mean wavelengths are 11.3. The size of the cellular pattern is comparable, in magnitude, to that of mesogranulation found by Novemberet al. (1981) on the velocitygram obtained at the Sacramento Peak Observatory. Then the cellular pattern revealed by the chain of granules in the present study may be bentatively identified as the mesogranulation. The possible physical connection between the mesogranulation and the clumpy assemblage of active granules is briefly discussed. 相似文献
16.
High-quality stratospheric photographs in the continuum were used to investigate spatial scales of the solar granulation field. Two-dimensional intensity power spectra are shown to contain most frequently the modes corresponding to the sizes of granules, protogranules, mesogranules, and supergranules. The place of these four, the most steady formations of the quiet Sun in the global structure of the solar photosphere, is discussed as well as their interconnection and their relation to weak and strong magnetic fields. The protogranulation scale is argued to play an important role in organization of the fine structure of the photosphere and magnetic fields in the quiet and active regions of the Sun. 相似文献
17.
It is shown that sunspots as tracers can give the same results for the differential rotation of the solar photosphere as the Doppler-shift measurements, if the sunspots used have only insignificant motion relative to their immediate photospheric surroundings. 相似文献
18.
V. N. Krivodubskii 《Kinematics and Physics of Celestial Bodies》2012,28(5):232-238
We study the effects of two-dimensional turbulence generated in sunspot umbra due to strong magnetic fields and Alfven oscillations excited in sunspots due to relatively weak magnetic fields on the evolution of sunspots. Two phases of sunspot magnetic field decaying are shown to exist. The initial rapid phase of magnetic field dissipation is due to two-dimensional turbulence. The subsequent slow phase of magnetic field decaying is associated with Alfven oscillations. Our results correspond to observed data that provide evidence for two types of sunspot evolution. The effect of macroscopic diamagnetic expulsion of magnetic field from the convective zone or photosphere toward sunspots is essential in supporting the long-term stability and equilibrium of vertical magnetic flux tubes in sunspots. 相似文献
19.
本文对Ｏｓｈｅｒｏｖｉｃｈ的黑子返回磁通量模型作了适当的修改，使用黑子中心作为边界条件，用五种观测结果，导出了理论模型所需的五个主要参量，用半经验方法求得了黑子静力学模型的磁场、压力和温度等物理量．将此模型应用于一个中等大小的圆形对称黑子，可得到一个特解，结果发现我们的模型既能满足黑子的磁性质，同时又能满足合理的热力学量分布． 相似文献
20.
Using a magnetograph, we examine four sunspots for evidence of a magnetic canopy at the penumbra/photosphere boundary. The penumbral edge is determined from the photometric intensity and is defined to correspond to the value of the average intensity minus twice the standard deviation from the average. From a comparison of the location of this boundary with the location of contours of the vertical and horizontal components of the magnetic field, we conclude that the data are best represented by canopy-type fields close to all four sunspots. There is some evidence that the magnetic inclination in the canopies is 5°–15° with respect to the horizontal and that the canopy base height lies in the middle/upper photosphere. The observations further suggest that the magnetic canopy of a sunspot begins at its outer penumbral boundary. 相似文献