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1.
It is confirmed that the penumbral bright grains are moving towards the sunspots umbra. We find different proper motions of 0.08 to 0.33 km s–1 for different penumbrae and different reduction methods. The lifetimes of these bright grains are about 1.5 to 3 hr depending on the position in the penumbra. 相似文献
2.
Automatic Sunspots Detection on Full-Disk Solar Images using Mathematical Morphology 总被引：1，自引：0，他引：1
Sunspots are solar features located in active regions of the Sun, whose number is an indicator of the Sun’s magnetic activity.
Therefore accurate detection and classification of sunspots are fundamental for the elaboration of solar activity indices
such as the Wolf number. However, irregularities in the shape of the sunspots and their variable intensity and contrast with
the surroundings, make their automated detection from digital images difficult. Here, we present a morphological tool that
has allowed us to construct a simple and automatic procedure to treat digital photographs obtained from a solar telescope,
and to extract the main features of sunspots. Comparing the solar indices computed with our algorithm against those obtained
with the previous method exhibit an obvious improvement. A favorable comparison of the Wolf sunspot number time series obtained
with our methodology and from other reference observatories is also presented. Finally, we compare our sunspot and group detection
to that of other observatories. 相似文献
3.
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
4.
The ratio of penumbral to umbral area of sunspots is an important topic for solar and geophysical studies. Hathaway (Solar Phys.286, 347, 2013) found a curious behaviour in this parameter for small sunspot groups (areas smaller than 100 millionths of solar hemisphere, msh) using records from Royal Greenwich Observatory (RGO). Hathaway showed that the penumbra–umbra ratio decreased smoothly from more than 7 in 1905 to lower than 3 by 1930 and then increased to almost 8 in 1961. Thus, Hathaway proposed the existence of a secular variation in the penumbra–umbra area ratio. In order to confirm that secular variation, we employ data of the sunspot catalogue published by the Coimbra Astronomical Observatory (COI) for the period 1929?–?1941. Our results disagree with the penumbra–umbra ratio found by Hathaway for that period. However, the behaviour of this ratio for large (areas greater or equal than 100 msh) and small groups registered in COI during 1929?–?1941 is similar to data available from RGO for the periods 1874?–?1914 and 1950?–?1976. Nevertheless, while the average values and time evolution of the ratio in large groups are similar those for small groups according to the Coimbra data (1929?–?1941) it is not analogous for RGO data for the same period. We also found that the behaviour of the penumbra–umbra area ratio for smaller groups in both observatories is significantly different. The main difference between the area measurements made in Coimbra and RGO is associated with the umbra measurements. We would like to stress that the two observatories used different methods of observation and while in COI both methodology and instruments did not change during the study period, some changes were carried out in RGO that could have affected measurements of umbra and penumbra. These facts illustrate the importance of the careful recovery of past solar data. 相似文献
5.
Emission core widths of K Ca ii line in the umbra and penumbra of 9 sunspots and in their vicinity are measured. All sunspots are located near the solar disc center. Data on variation of widths W
K along the mean sunspot radius are obtained. Values W
K in the umbra and penumbra centers are equal or somewhat less than on stars of the same luminosity. 相似文献
6.
G. Ekmann 《Solar physics》1974,38(1):73-75
Based on pinhole photometer observations in 4–6 wavelength regions we have searched for a connection between the intensities of the umbra and the penumbra of sunspots. For the 1.67 μm wavelength region it is apparent that spots with dark umbrae also have dark penumbrae. In the other wavelength regions similar relations are found. The darkness of the spot is probably connected with the degree of complexity of the spot. 相似文献
7.
O. S. Gopasyuk 《Kinematics and Physics of Celestial Bodies》2010,26(5):242-248
Torsional oscillations of seven single spots are studied based on the observations of the longitudinal magnetic field and
the field of radial velocities in the photospheric Fe I λ 525.3 nm line. The periods of umbra and penumbra oscillations are
2.2–7.1 and 3.3–7.7 days, respectively. The spots at a greater solar latitude are characterized by a longer period of oscillations
and a smaller axial strength of the magnetic field. The periods of umbra and penumbra oscillations increase with an increase
in the period and amplitude of the sunspot umbra oscillations. The obtained results can point to a unitary mechanism of torsional
oscillations of umbra and penumbra of single spots and a connection of these oscillations with the differential rotation of
the Sun. 相似文献
8.
We report on three sequences of high-resolution white-light and magnetogram observations obtained in the summer of 1989. The duration of sub-arcsecond seeing was three to four hours on each day. Study of the white-light and magnetogram data yields the following results:
- For all but one of the sunspots we have observed, both dark fibrils and bright grains in the inner part of the penumbra of sunspots move toward the umbra with a speed of about 0.5 km s-1. In the outer part of the penumbra, movement is away from the umbra. The one exception is a newly formed spot, which has inflow only in its penumbra.
- Granular flows converge toward almost every pore, even before its formation. Pores are observed to form by the concentration of magnetic flux already existing in the photosphere. The pores (or small sunspots), in turn, then move and concentrate to form bigger sunspot.
- We followed an emerging flux region (EFR) from 29 to 31 July, 1989 that was composed of a large number of bipoles with magnetic polarities mixed over a large area in the first day of its birth. As time went on, polarities sorted out: the leading polarity elements moved in one direction; the following, the opposite. During the process a large number of cancellations occurred, with some sub-flares and surges observed simultaneously. After about 24 hours, the positive and negative fluxes were essentially separated.
- We find two kinds of photospheric dark alignments in the region of new flux emergence: (a) alignments connecting two poles of opposite magnetic polarity form the tops of rising flux tubes; (b) alignments corresponding to the magnetic flux of one polarity, which we call elongated pores.
9.
High-resolution MDI magnetograms are used to study the pattern of moving magnetic inhomogeneities in sunspots. We examine the inward and outward moving features in sunspots. The velocity of these features is small in the umbra while it is about 0.5 km s–1 in the outer penumbra. The inward and outward moving features may be the possible origin for the long-term fluctuations of magnetic field strength in sunspots. 相似文献
10.
《Chinese Astronomy and Astrophysics》2020,44(4):462-473
Sunspots are solar features located in active regions of the Sun, whose number is an indicator of the Sun's magnetic activity. With a substantial increase in the quantity of solar image data, the automated detection and verification of various solar features have become increasingly important for the accurate and timely forecasts of solar activity and space weather. In order to use the high time-cadence SDO/HMI data to extract the main sunspot features for forecasting solar activities, we have established an automatic detection method of sunspots based on mathematical morphology, and calculated the sunspot group area and sunspot number. By comparing our results with those obtained from the Solar Region Summary compiled by NOAA/SWPC, it is found that the sunspot group areas and sunspot numbers computed with our algorithm are in good agreement with the active region values released by SWPC, and the corresponding correlation coefficients for the sunspot group area and sunspot number are 0.77 and 0.79, respectively. By using the method of this paper, the high time-cadence feature parameters can be obtained from the HMI data to provide the timely and accurate inputs for the solar activity forecast. 相似文献
11.
We describe a procedure for automated detection of sunspots from SoHO/MDI full-disk continuum images. The MDI Level-1.8 continuum images were first corrected for the limb darkening and stray light, and then were flat-fielded. Sunspots were extracted using a newly developed automated sunspot detection procedure, which is based on the level set, namely the selective binary and Gaussian function regularized level set (SBGFRLS) method (Zhang et al., Image Vis. Comput. 28, 668, 2010). In this method we initialize a two-dimensional level-set function and evolve it using a signed pressure force (SPF) function. For sunspot detection, the level-set function was defined twice, first for umbra and then for penumbra extraction. Using this procedure, along with the characterization of detected sunspots we have also generated tracking reports of all sunspots in a fully unsupervised manner. 相似文献
12.
The increased amount of information provided by ongoing missions such as the Solar Dynamics Observatory (SDO) represents a great challenge for the understanding of basic questions such as the internal structure of sunspots and how they evolve with time. Here, we contribute with the exploitation of new data, to provide a better understanding of the separate growth and decay of sunspots, umbra, and penumbra. Using fuzzy sets to compute separately the areas of sunspot umbra and penumbra, the growth and decay rates for active regions NOAA 11117, NOAA 11428, NOAA 11429, and NOAA 11430 are computed from the analysis of intensitygrams obtained by the Helioseismic and Magnetic Imager onboard SDO. A simplified numerical model is proposed for the decay phase, whereby an empirical irrotational and uniformly convergent horizontal velocity field interacting with an axially symmetric and height-invariant magnetic field reproduces the large-scale features of the much more complex convection observed inside sunspots. 相似文献
13.
Philip A. Isenberg 《Solar physics》1976,50(1):49-63
The boundary between the umbra and penumbra of a sunspot is consistently observed to be very sharp, on the order of 500 km. Approximating the sunspot as a static region in a homogeneous medium with a radiative surface, temperature distributions resulting from a variety of convective motions exterior to the sunspot are calculated. The calculations suggest that, for the exterior convection to produce the observed boundary, the maximum depth of the region of inhibited convection below a sunspot umbra is on the order of 103 km. 相似文献
14.
The first statistical results in sunspot distributions in 1996–2004 obtained from the Solar Feature Catalogues (SFC) are presented.
A novel robust technique is developed for automated identification of sunspots on SOHO/MDI white-light (WL) full-disk solar
images. The technique applies image standardization procedures for elimination of the limb darkening and non-circular image
shape, uses edge-detection methods to find the sunspot candidates and their edges and morphological operations to smooth the
features and fill in gaps. The detected sunspots are verified with the SOHO/MDI magnetograms by strong magnetic fields being
present in sunspots. A number of physical and geometrical parameters of the detected sunspot features are extracted and stored
in the relational SFC database including umbra/penumbra masks in the form of run-length data encoding of sunspot bounding
rectangles. The detection results are verified by comparison with the manual daily detection results in Meudon and Locarno
Observatories in 2002 and by correlation (about 96%) with the 4 year sunspot areas produced manually at NOAA. Using the SFC
data, sunspot area distributions are presented in different phases of the solar cycle and hemispheres which reveals a periodicity
of the north–south asymmetry with a period of about 7–8 years. The number of sunspots increases exponentially with the area
decrease with the index slightly increasing from −1.15 (1997) to −1.34 (2001). 相似文献
15.
The peculiarities of magnetosensitive lines in the penumbral spectrum and the abnormal distribution of circular polarization in them are explained satisfactorily in terms of superposition of radiation originating in different elements of penumbral fine structure. Complicated asymmetric rv
– contours can be represented as a sum of two components related to bright (BR) and dark (DR) penumbral regions. Crossover effect in sunspot penumbra appears, when there is considerable relative radial mass velocity in BR and DR, having the magnetic field of different polarities in them. Such conditions are supposed to exist in the penumbra of some sunspots, situated close to the solar limb. 相似文献
16.
Most of our knowledge about the Sun's activity cycle arises from sunspot observations over the last centuries since telescopes have been used for astronomy. The German astronomer Gustav Spörer observed almost daily the Sun from 1861 until the beginning of 1894 and assembled a 33‐year collection of sunspot data covering a total of 445 solar rotation periods. These sunspot drawings were carefully placed on an equidistant grid of heliographic longitude and latitude for each rotation period, which were then copied to copper plates for a lithographic reproduction of the drawings in astronomical journals. In this article, we describe in detail the process of capturing these data as digital images, correcting for various effects of the aging print materials, and preparing the data for contemporary scientific analysis based on advanced image processing techniques. With the processed data we create a butterfly diagram aggregating sunspot areas, and we present methods to measure the size of sunspots (umbra and penumbra) and to determine tilt angles of active regions. A probability density function of the sunspot area is computed, which conforms to contemporary data after rescaling. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
Time series of the nonsplit Fei 7090 Å line have been observed in several sunspots with a 100 x 100 diode array corresponding to 48 arc sec times 1.39 Å. The spatial behaviour of Doppler motions along one fixed slit position has been studied as a function of time. Former results are confirmed, that the power in the five minute range decreases from the photosphere to the umbra, where, however, values still well above the noise level are measured. Regarding the penumbra, the power tends to exhibit a maximum at locations where the line-of-sight component of a radial horizontal field should be maximal. This indicates that the direction of the oscillatory velocities might be influenced by the magnetic field or the Evershed flow. No significant power is found in the 3 min range. An exception might be seen in a small patch at the limb of the umbra of one spot. 相似文献
18.
Heat transport in the Sun is describable by a Fokker-Planck, or diffusion, transfer equation. A study of the general character of the solutions of the transfer equation shows that the inhibition of convective transport beneath the photosphere produces a photospheric dark ring surrounded by a bright ring, or at best, a dark area surrounded by a bright ring. The mean temperature beneath the sunspot is unavoidably above normal, so that the enhanced gas pressure would disperse, rather than concentrate, the magnetic field. Hence we conclude that the inhibition of convection cannot be the cause of a sunspot.We suggest, instead, that a sunspot is a region of enhanced, rather than inhibited, energy transport and emissivity. The magnetic field of the sunspot causes a dynamical overstability in the outer thousand km of the convective zone, generating copious fluxes of hydromagnetic waves, which propagate rapidly out of the region along the magnetic field. We suggest that this heat engine is so efficient as to convert at least three fourths of the heat flux into waves. Solutions of the heat transport equation in the presence of a heat sink automatically resemble the observed sunspot, including a dark interior, a sharp transition at the edge of the umbra, and an extended grey area around the outside, the penumbra. The mean temperature is reduced, causing the observed concentration of the magnetic field.The enhanced radiation is in the form of hydromagnetic waves, which do not appear in ordinary photographs, but which light up the sky over the sunspot in a manner conspicuous in any UV or X-ray picture. In this respect, then, a sunspot is effectively a hole in the Sun, extending down to temperatures of 2 × 104 K or more.This work was supported in part by the National Aeronautics and Space Administration under Grant NGL 14-001-001. 相似文献
19.
The area ratio of umbra to penumbra (Au/Ap) was investigated for a series of 126 sunspots observed around the maximum of solar activity in 1980. Plotting log (Au) as function of log (Ap) a linear relation is obtained with a slope of 1.10, yielding an average ratio Au/Ap of 0.24 for small spots and of 0.32 for large spots. This deviates noticeably from the commonly adopted constant value of Au/Ap = 0.21 (Allen, 1973) used e.g. for modelling the sunspot irradiance deficit (cf. Willson et al., 1981) from the Solar Geophysical Data.Mitteilungen aus dem Kiepenheuer-Institut Nr. 328 相似文献
20.
《New Astronomy》2024
A huge collection of solar images to visualize sunspot are acquired by various solar observatories spread across the globe. This necessitates efficient tools for detecting and analyzing the sunspots encompassing diverse solar features. One such contribution is delivered in this work by exploiting the intrinsic intensity variations of solar images associated with sunspots and their attributes. The presented mechanism initially, pre-processes the acquired solar images by correcting the intensity variations introduced while profiling from the sun center to the limb followed by smoothening using a localized window. The resultant is then differenced from the global threshold that is obtained as a result of the statistical analysis computed over the probability distribution function of the input image. This arrangement offers higher discerning variations concerned with the local contextual structures related to sunspot, umbra, and penumbra. Also, it captures the major gradient variation between these regions that adds to the pixel heterogeneity surrounding them to finally render an automatic sunspot detection mechanism distinguishing the diverse solar regions. Receiver Operating Characteristics (ROC) investigation on annual solar images in Flexible Image Transport System (FITS) format reveals the presented method’s efficacy. Also, Pearson correlation analysis of the evaluated sunspot numbers from the detected sunspots with the solar catalog reveals the scheme’s detection closeness. Moreover, the model’s simplicity analyzed along the time and space dimensions affirms its extension to real-time analysis 相似文献