共查询到20条相似文献，搜索用时 26 毫秒
1.
The time and spatial characteristics of 324 large sunspots (S50 millionths of the solar hemisphere) selected from the Abastumani Astrophysical Observatory photoheliogram collection (1950–1990) have been studied. The variations of sunspot angular rotation velocity residuals and oscillations of sunspot tilt angle were analyzed. It has been shown that the differential rotation rate of selected sunspots correlates on average with the solar cycle. The deceleration of differential rotation of large sunspots begins on the ascending arm of the activity curve and ends on the descending arm reaching minimum near the epochs of solar activity maxima. This behavior disappears during the 21st cycle. The amplitudes and periods of sunspot tilt-angle oscillations correlate well with the solar activity cycle. Near the epochs of activity maximum there appear sunspots with large amplitudes and periods showing a significant scatter while the scatter near the minimum is rather low. We also found evidence of phase difference between the sunspot angular rotation velocity and the amplitudes and periods of tilt-angle oscillations. 相似文献
2.
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
3.
L. Gy?ri 《Solar physics》2012,280(2):365-378
Sunspot and white light facular areas are important data for solar activity and are used, for example, in the study of the evolution of sunspots and their effect on solar irradiance. Solar Dynamic Observatory??s Helioseismic and Magnetic Imager (SDO/HMI) solar images have much higher resolution (??0.5????pixel?1) than Solar and Heliospheric Observatory??s Michelson Doppler Imager (SOHO/MDI) solar images (??2????pixel?1). This difference in image resolution has a significant impact on the sunspot and white light facular areas measured in the two datasets. We compare the area of sunspots and white light faculae derived from SDO/HMI and SOHO/MDI observations. This comparison helps the calibration of the SOHO sunspot and facular area to those in SDO observations. We also find a 0.22 degree difference between the North direction in SDO/HMI and SOHO/MDI images. 相似文献
4.
A new method to detect sunspots on full-disk solar images, recorded in an optical wide spectral band and in the line of Ca ii K1, is presented. It is based on the compact wavelet transform and a process that automatically identifies the noise in the images of the Sun. This method estimates also its center and the limb positions with a precision of a few milliarcseconds. Precisions of 1 and 8 milliarcseconds are, respectively, found for the disk center position and the radius of simulated solar images. The results obtained on sunspot identification on solar images recorded during April 2002 at Meudon Observatory (France) reveal that we are able to detect 3.35 % additional sunspots compared to a manual method. Our method preserves the sunspot areas better than 95 %. 相似文献
5.
Long-term homogeneous observations of solar activity or many solar cycles are essential for investigating many problems in solar physics and climatology. The one key parameter used in most long-term studies is the Wolf sunspot number, which is susceptible to observer bias, particularly because it is highly sensitive to the observer's ability to see the smallest sunspots. In this paper we show how the Wolf sunspot number can be derived from the number of sunspot groups alone. We utilize this approach to obtain a Group Wolf number. This technique has advantages over the classical method of determining the Wolf number because corrections for observer differences are reduced and long-term self-consistent time series can be developed. The level of activity can be calculated to an accuracy of ± 5% using this method. Applying the technique to Christian Horrebow's observations of solar cycles 1, 2, and 3 (1761–1777), we find that the standard Wolf numbers are nearly homogeneous with sunspot numbers measured from 1875 to 1976 except the peak of solar cycle 2 is too low by 30%. This result suggests that further analyses of early sunspot observations could lead to significant improvements in the uniformity of the measurements of solar activity. Such improvements could have important impacts upon our understanding of long-term variations in solar activity, such as the Gleissberg cycle, or secular variations in the Earth's climate. 相似文献
6.
It is well known that sunspots are dark. This statement is not correct in the sunspot atmosphere between the chromosphere and the corona, where sunspots often are brighter than their surroundings. The brightest feature in the sunspot transition region is called a sunspot plume. Not all sunspots contain a plume. We find that 20 out of 21 sunspots show a plume when one magnetic polarity dominates the sunspot region out to a distance of 50 from the sunspot. Most sunspots show downflows that exceed 25 km s–1 in the sunspot plumes at temperatures close to 250000 K. This downflow is not maintained by inflow from the corona, but by gas at transition region temperatures, streaming in flow channels from locations well outside the sunspot. We suggest that this inflow is a necessary requirement for the sunspot plume to occur and present a working hypothesis for the origin of sunspot plumes. This paper is the first thorough spectral analysis of sunspot plumes. It is based on simultaneous observations of ten or six EUV emission lines in 42 sunspot regions with the Coronal Diagnostic Spectrometer – CDS on the Solar and Heliospheric Observatory – SOHO. The line profiles are studied in detail with another SOHO instrument, the Solar Ultraviolet Measurements of Emitted Radiation – SUMER. 相似文献
7.
We present a search for the acoustic oscillation deficit which may exist at the antipodes of sunspots. Dopplergrams from Big Bear Solar Observatory 1988 helioseismology data were selected for five days on which large sunspots were known to be on the unseen hemisphere of the Sun. Acoustic oscillation amplitudes in the antipodal regions of these sunspots were compared with amplitudes in surrounding quiet-Sun regions. We did not detect a statistically significant acoustic amplitude deficit in our data. Our results indicate that the amplitude deficit at the sunspot antipodal points is limited to no more than 3% of the acoustic amplitude in the region, for solar oscillation modes of spherical harmonic degree l 200. We conclude that no strong acoustic deficit exists at the antipodes of sunspots. A more sensitive search, requiring more elaborate observations than we have performed, would be desirable in order to determine if a weak acoustic amplitude deficit exists at some level at the antipodes of sunspots, perhaps at higher spatial frequencies of oscillation. The noise level in any signals detected by such observations would probably limit their usefulness as seismic probes. However, information on the lifetimes of solar oscillation modes can be deduced even if no acoustic amplitude deficit is detected. 相似文献
8.
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
9.
R. T. Stewart 《Solar physics》1985,96(2):381-395
A synoptic study of the occurrence and polarization of 160 MHz noise storms recorded at Culgoora during the current solar cycle shows that the storm sources occur in large unipolar cells extending >90° in solar longitude and 60° in latitude, with lifetimes of 1 yr. From solar maximum onwards these large cells stretch across the solar equator to form a longitudinal sector pattern reminiscent of that observed in the interplanetary magnetic field. Comparisons with published heliospheric current sheet simulations support this conclusion. The noise storms occur in the strong magnetic fields above large, complex, flare-active sunspots. Unlike most active regions, those associated with noise storms do not always have dominant sunspots as leaders. Rather, about one-third have the dominant sunspot as a follower. The dominant sunspot polarities tend to agree with the long-lived sector structure, implying that emerging magnetic flux occurs at preferred longtitudes on the solar surface. 相似文献
10.
The extremely low sunspot activity during the period of the Maunder minimum 1645–1715 was confirmed by group sunspot numbers, a new sunspot index constructed by Hoyt and Schatten (1998a,b). Neither sunspots nor auroral data time behavior indicate the presence of 11-year solar cycles as stated by Eddy (1976). The evidence for solar cycles was found in the butterfly diagram, constructed from observations made at Observatoire de Paris. After Clivier, Boriakoff, and Bounar (1998) the solar cycles were reflected also in geomagnetic activity. Results are supported by the variation of cosmogenic isotopes 10Be and 14C. The majority of the observed 14 naked-eye sunspots occurred on days when telescopic observations were not available. A part of them appeared in the years when no spot was allegedly observed. Two-ribbon flares appear in plages with only very small or no sunspots. Some of these flares are geoactive. Most aurorae (90%), which were observed during the Maunder minimum, appeared in years when no spot was observed. Auroral events as a consequence of proton flares indicate that regions with enhanced magnetic field can occur on the Sun when these regions do not produce any sunspots. 相似文献
11.
《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
12.
We applied automatic identification of sunspot umbrae and penumbrae to daily observations from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to study their magnetic flux density (B) and area (A). The results confirm an already known logarithmic relationship between the area of sunspots and their maximum flux density. In addition, we find that the relation between average magnetic flux density ( $B_{\rm avg}$ ) and sunspot area shows a bimodal distribution: for small sunspots and pores (A≤20 millionth of solar hemisphere, MSH), $B_{\rm avg} \approx 800~\mbox{G}$ (gauss), and for large sunspots (A≥100 MSH), $B_{\rm avg}$ is about 600 G. For intermediate sunspots, average flux density linearly decreases from about 800 G to 600 G. A similar bimodal distribution was found in several other integral parameters of sunspots. We show that this bimodality can be related to different stages of sunspot penumbra formation and can be explained by the difference in average inclination of magnetic fields at the periphery of small and large sunspots. 相似文献
13.
The Extreme Limb Photometer (ELP) has been used to measure the irradiance fluctuation of the Sun due to selected active regions. Forty-five active regions that were completely scanned at various disk positions are included in the analysis. The contribution of these active regions to a global solar irradiance fluctuation has been correlated with photometric sunspot and facular indices (PSI and PFI) using published values of sunspot and calcium plage areas. The measured ELP fluctuations are converted to a global brightness fluctuation, B/B. The sunspot component of B/B correlates with PSI with r = 0.95. The facular component of B/B correlates with PFI with r - 0.72. The expression for PFI is important to the question of energy balance between sunspots and faculae and the results presented here are not incompatible with energy balance between the two phenomena; that is the energy deficit of sunspots may be balanced by the energy excess of faculae. 相似文献
14.
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
15.
N. R. Sheeley Jr. 《Solar physics》1969,9(2):347-357
A time-lapse sequence of spectroheliograms in the bandhead of CN at λ3883 reveals the following behavior of the photospheric network with time:
- There is a steady flow of bright ‘points’ (? 1000 km in diameter) laterally outward from sunspots at speeds on the order of 1 km·sec?1. After traveling about 10 000 km from a sunspot they either conglomerate to form fragments of the photospheric network or disappear.
- Spatial changes in the network pattern seem to take place by means of the shifting of network fragments laterally on the solar surface. Although most small-scale details are recognizable after 5–10 minutes, within 30 minutes nearly all the details have changed completely. In contrast to this, the large-scale network pattern seems relatively unchanged after 2 1/2 hours.
- Occasionally ‘new’ network, not resulting from the lateral motion of bright features from either previously existing network or sunspots, appears on the solar surface. This process consists of the formation in approximately 10 minutes of bright points and a darker-than-average feature between them. The dark feature disappears in another 5–10 minutes and the bright points separate at a relative speed of a few km·sec?1. If the event is of a sufficiently large magnitude, a sunspot will appear.
16.
17.
In the bookMachina Coelestis (1679), Johannes Hevelius lists his daily solar observations from 1653 to 1679. He mentions 19 sunspot groups during this interval, of which 14 are unique to Hevelius and five are confirmed by other observers. There are an additional 9 sunspot groups during this interval that were not observed by Hevelius. In five cases he was not observing, but in the other four cases he did observe but failed to comment upon sunspots. The spots he missed or failed to observe tend to occur near the end of his career. This suggests Hevelius occasionally missed sunspots but usually was a reliable observer. These observations are important because they provide us the only known daily listing of solar observations during the early years of the Maunder Minimum. They are also important because they were overlooked by Wolf, Spoerer, Maunder, Eddy, and others in their study of solar activity in the seventeenth century. They provide us the best record of the sunspot maximum of 1660 when one sunspot lasted at least 86 days as it traversed the solar disk four times. The same region was active for seven solar rotations. 相似文献
18.
Saken Obashevich Obashev Rimma Khaliullovna Gainullina Tamara Mikhajlovna Minasyants Gennadij Sergeevich Minasyants 《Solar physics》1982,78(1):59-66
The Wilson effect, used before only as a method of determining the physical depression of sunspots, is used here to estimate a quite different parameter - the sunspot symmetry axis inclination angle to the solar surface, this explains the observed negative Wilson effect.On the basis of photoheliograms taken with three telescopes of the High-Altitude Solar observatory Peak Alma-Ata, the Wilson effect for the whole solar disk is investigated, the east and west parts of the disk being studied separately. 111 sunspots of regular shape at different heliocentric angles were measured, eight of them being under observations from one limb to the other. To study the dependence of the Wilson effect on the heliocentric angle, all observations within an angular interval of 10° were averaged. The dependence thus derived is described by two sinusoids having the zero point shifted along both axes. The shift of the zero Wilson effect to the west, i.e., a shift along the heliocentric angle axis, can be caused by the deviation of the sunspot axis to the east from the normal to the solar surface. On the line of sight-normal plane the angle corresponding to this deviation is =34°±14°. 相似文献
19.
Observations of sunspot transition region oscillations 总被引：1，自引：0，他引：1
Oscillations with a period of 3 minutes are observed in the transition region of six sunspots with the Solar and Heliospheric Observatory - SOHO joint observing programme for velocity fields in sunspot regions. Observations of the transition region lines Ov 629 and Nv 1238, 1242 with the SUMER instrument show significant differences in the amplitude of the 3-minute oscillations from one sunspot to another, both in intensity and line-of-sight velocity. In four sunspots the central part of the umbra is observed. Two of these sunspots show coincidence between the maxima in peak line intensity and velocity directed towards the observer, as is expected for an upward-propagating acoustic wave. The two other sunspots show large oscillation amplitudes and a difference of 25° between maxima in intensity and blue shift. The possible effect of partial wave reflection on the observed phase relation is discussed. For one sunspot only a part of the umbra, close to the penumbra, was observed and the observations show a difference of 50° between maxima in intensity and blueshift. For the smallest sunspot the observations are found to be contaminated by contributions from an area without oscillations. Observed oscillations in line width are small, but probably significant in two sunspots. The observations of NOAA 8378 allow us to compare simultaneous recordings of the oscillations in the chromospheric Siii 1260 line with the oscillations in the transition region lines. We question the suggestion by Fludra (1999) that the sunspot transition region oscillations are a typical feature of the sunspot plumes. 相似文献
20.
对太阳大气磁场的可靠测量有助于人们更好地理解太阳活动区内外的许多活动现象,如耀斑的触发和能量释放过程、黑子的形态和黑子大气的平衡、日珥的形成等.由于原子在磁场中的一些能级会产生分裂(Zeeman效应),使对应这些能级的谱线分裂成若干个具有不同偏振特性的分量,因此目前对黑子磁场的测量主要是通过偏振光,即Stokes参量I、Q、U、V的观测来实现的.该文主要介绍近30年来太阳黑子光谱反演的方法以及所取得的成就;同时也对光谱反演和滤光器型的望远镜矢量磁场的测量进行了简单的比较. 相似文献