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1.
The change in facular area around decaying sunspots is investigated. The data are from full-disk photometric images from CFDT1 (5 arc sec pixels) obtained at the Ca ii K-line = 393.4 nm. The 31 active regions are from a list previously used to study the decay rate of sunspots. We find a weak, marginally significant relation between spot decay rate and growth of the surrounding facular region (r2 = 0.1255). We conclude that, for this group of decaying sunspots, the growth or decay of the surrounding facular region was not clearly related to the decay rate of an active regions sunspots. 相似文献
2.
In a statistical study of the decay of individual sunspots based on DPR data we find that the mean instantaneous area decay rate is related to the spot radius ro and the maximum radius ro as D = CD r/ro, CD = 32.0±0.26 MSH day -1. This implies that sunspots on the mean follow a parabolic decay law; the traditional linear decay law is excluded by the data. The validity of the Gnevyshev–Waldmeier relationship between the maximum area A 0 and lifetime T of a spot group, A0/T 10 MSH day-1, is also demonstrated for individual sunspots. No evidence is found for a supposed supergranular quantization of sunspot areas. Our results strongly support the recent turbulent erosion model of sunspot decay while all other models are excluded. 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.
Variations in total solar irradiance (TSI) correlate well with changes in projected area of photospheric magnetic flux tubes
associated with dark sunspots and bright faculae in active regions and network. This correlation does not, however, rule out
possible TSI contributions from photospheric brightness inhomogeneities located outside flux tubes and spatially correlated with them. Previous reconstructions of TSI report agreement with radiometry that seems to rule out significant “extra-flux-tube” contributions.
We show that these reconstructions are more sensitive to the facular contrasts used than has been generally recognized. Measurements
with the Solar Bolometric Imager (SBI) provide the first reliable support for the relatively high, wide-band, disk-center
contrasts required to produce 10% rms agreement. Longer term bolometric imaging will be required to determine whether the
small but systematic TSI residuals we see here are caused by remaining errors in spot and facular areas and contrasts or by
extra-flux-tube brightness structures such as bright rings around sunspots or “convective stirring” around active regions. 相似文献
5.
We study the influence of faculae on sunspot heat blockage using a thermal model based on eddy heat diffusion through the convection zone. The facula is represented as a localized area of excess emission surrounding the sunspot, which is represented as a thermal plug. Our computations using a range of reasonable combinations of spot and facular depths show no significant influence of the facula on the long storage times of heat blocked by sunspots. However, the local cooling of surface layers produced by excess facular emission in this model propagates globally within the convection zone in a similar way to the heating produced by a spot. The net effect of spots and faculae on L
over time scales longer than an active region lifetime should thus be determined by the global sum of sunspot flux deficits and facular excesses. 相似文献
6.
Plage areas and intensities derived from CaII K spectroheliograms are used as a proxy for the facular irradiance excess of solar active regions for the period 19 August to 4 September 1980. Using a calibration method proposed by Vrnak et al. (1991), the photospheric facular index (PFI) with constant facular contrastC
p
= 0.018 is replaced by a variableC
p
, depending on the plage brightness. A sgnificant increase ofC
p
from 0.015 to 0.025 is found for plage areas varying from a few to approx. 6 · 103 millionths hemispheres.Combining the facular irradiance excess with sunspot deficits (as determined for the same period by Steinegger et al. 1990) yields good aggrement with the irradiance variations measured by ACRIM I, using a center-to-limb variation ofC
p
according to Chapman and Meyer (1986). The ratio of facular excess to sunspot deficit (integrated over solid angle 2) decreases from values of 1.5 to 2 for regions with sunspot areas below 100 millionths hemispheres to 0.2 for sunspots of areas > 1000 millionths hemispheres, 相似文献
7.
Results are presented from a study of various sunspot contrast parameters in broadband red (672.3 nm) Cartesian full-disk
digital images taken at the San Fernando Observatory (SFO) over eight years, 1997 – 2004, of the twenty-third sunspot cycle.
A subset of over 2700 red sunspots was analyzed and values of average and maximum sunspot contrast as well as maximum umbral
contrast were compared to various sunspot parameters. Average and maximum sunspot contrasts were found to be significantly
correlated with sunspot area (r
s=− 0.623 and r
s=− 0.714, respectively). Maximum umbral contrast was found to be significantly correlated with umbral area (r
s=− 0.535). These results are in agreement with the works of numerous other authors. No significant dependence was detected
between average contrast, maximum contrast, or maximum umbral contrast during the rising phase of the solar cycle (r
s=0.024, r
s=0.033, and r
s=0.064, respectively). During the decay phase, no significant correlation was found between average contrast or maximum contrast
and time (r
s=− 0.057 and r
s=0.009, respectively), with a weak dependence seen between maximum umbral contrast and cycle (r
s=0.102). 相似文献
8.
As a first step in constructing three-dimensional decaying sunspot models we select the relevant observational data. From these we conclude:
- sunspots, except the smallest, obey a radial and evolutionary similarity;
- sunspots may be considered as isolated, fairly well defined flux tubes, wrapped in thin current sheets;
- a substantial number among stable regular spots show a phase of slowest decay whose rate is independent of the spot's area.
9.
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
10.
We examine daily records of sunspot group areas (measured in millionths of a solar hemisphere or μHem) for the last 130 years
to determine the rate of decay of sunspot group areas. We exclude observations of groups when they are more than 60° in longitude
from the central meridian and only include data when at least three days of observations are available following the date
of maximum area for a group’s disk passage. This leaves data for over 18 000 measurements of sunspot group decay. We find
that the decay rate increases linearly from 28 μHem day−1 to about 140 μHem day−1 for groups with areas increasing from 35 μHem to 1000 μHem. The decay rate tends to level off for groups with areas larger
than 1000 μHem. This behavior is very similar to the increase in the number of sunspots per group as the area of the group
increases. Calculating the decay rate per individual sunspot gives a decay rate of about 3.65 μHem day−1 with little dependence upon the area of the group. This suggests that sunspots decay by a Fickian diffusion process with
a diffusion coefficient of about 10 km2 s−1. Although the 18 000 decay rate measurements are lognormally distributed, this can be attributed to the lognormal distribution
of sunspot group areas and the linear relationship between area and decay rate for the vast majority of groups. We find weak
evidence for variations in decay rates from one solar cycle to another and for different phases of each sunspot cycle. However,
the strongest evidence for variations is with latitude and the variations with cycle and phase of each cycle can be attributed
to this variation. High latitude spots tend to decay faster than low latitude spots. 相似文献
11.
Robert F. Howard 《Solar physics》1992,137(1):51-65
Digitized Mount Wilson sunspot data from 1917 to 1985 are analyzed to examine the growth and decay rates of sunspot group umbral areas. These rates are distributed roughly symmetrically about a median rate of decay of a few hemisphere day-1. Percentage area change rates average 502% day-1 for growing groups and -45% day-1 for decaying groups. These values are significantly higher than the comparable rates for plage magnetic fields because spot groups have shorter lifetimes than do plages. The distribution of percentage decay rates also differs from that of plage magnetic fields. Small spot groups grow at faster rates on average than they decay, and large spot groups decay on average at faster rates than they grow. Near solar minimum there is a marked decrease in daily percentage spot area growth rates. This decrease is not related to group area, nor is it due to latitude effects. Sunspot groups with rotation rates close to the average (for each latitude) have markedly slower average rates of daily group growth and decay than do those groups with rotation rates faster or slower than the average. Similarly, sunspot groups with latitude drift rates near zero have markedly slower average rates of daily group growth and decay than do groups with significant latitude drifts in either direction. Both of these findings are similar to results for plage magnetic fields. These various correlations are discussed in the light of our views of the connection of the magnetic fields of spot groups to subsurface magnetic flux tubes. It is suggested that a factor in the rates of growth or decay of spot groups and plages may be the inclination angle to the vertical of the magnetic fields of the spots or plages. Larger inclination angles may result in faster growth and decay rates.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation. 相似文献
12.
We have measured the motion of facular points and granules in the same region near a decaying sunspot. It is found that both features move away across the moat surrounding the sunspot. The mean speed of facular points is larger than that of granules: 0.65 km s–1 and 0.4 km s–1, respectively. These results are consistent with previous measurements of the speed of bright network features and moving magnetic fields, as well as of non-magnetic photospherical material. They support models in which a decaying sunspot is at the center of a supergranule, whose horizontal motions sweep out granules and magnetic flux tubes associated to the facular points. It is also found that granules are dragged by supergranular motions away of the moat.Contributions from the Kwasan and Hida Observatories, University of Kyoto.A part of this work was done while one of the authors (R.M.) was staying at the Kwasan and Hida Observatories, University of Kyoto, Japan, as a JSPS research fellow. 相似文献
13.
Peter Foukal 《Solar physics》1993,148(2):219-232
We analyze the record of facular areas compiled by the Royal Greenwich Observatory (RGO) from daily white-light observations between 1874 and 1976. Curiously, the relative amplitudes of the three largest sunspot cycles 17, 18, and 19 in this record are reversed when they are ranked by facular area. We show that this negative correlation arises from a general decrease of the ratioA
F/A
S, of facular to sunspot area, with increasingA
S. Within a given cycle,A
F/A
Sdecreases in active regions of largeA
S, butA
F/A
Sis also lower at allA
S, in cycles of higher peak amplitude inA
S. This decrease ofA
F/A
Sin large spot groups is consistent with its decrease in younger, more active solar-mass stars, and it may explain why stars only slightly more magnetically active than the Sun tend to exhibit much greater variability in broad-band photometry. We suggest that the physical explanation is an increased spatial filling factor of magnetic flux, favoring formation of sunspots over faculae. We also explain why the decrease inA
F/ASis not seen in the disc-integrated Ca K plage areas, nor in theF10.7 microwave index, both of which exhibit remarkable linearity when plotted against smoothed sunspot area. This explanation suggests how complementary data on faculae and plages from RGO and Mt. Wilson could be used to improve empirical models of total irradiance variation, extending back to 1874. 相似文献
14.
We study the relationship between the brightness (I) and magnetic field (B) distributions of sunspots using 272 samples observed at the San Fernando Observatory and the National Solar Observatory,
Kitt Peak, whose characteristics varied widely. We find that the I – B relationship has a quadratic form for the spots with magnetic field less than about 2000 G. The slope of the linear part
of the I – B curve varies by about a factor of three for different types of spots. In general the slope increases as the spot approaches
disk center. The I – B slope does not have a clear dependency on the spot size but the lower limit appears to increase as a function of the ratio
of umbra and penumbra area. The I – B slope changes as a function of age of the sunspots. We discuss various sunspot models using these results. 相似文献
15.
Observations of facular regions on 35 days during 1982 obtained with the Extreme Limb Photometer are reported. The data were obtained at a wavelength of 0.53 m with two apertures, No. 1 covering 36 arc sec and No. 2 covering 11 arc sec, inwards from the limb. The mean contrasts for all regions detected are 1.05 ± 0.12% and 1.59 ± 0.16%, respectively. The mean contrast of the faculae closer to the limb (aperture 2) is 1.51 ± 0.23 times that from aperture No. 1. This contrast ratio can be fit to a
–1-curve. These results are consistent with those from 1975 and 1979 observations and may be consistent with the facular limb-darkening function determined by Libbrecht and Kuhn (1984, 1985) if our data are normalized by the area of the solar surface. However, no calibrations or corrections are required to obtain the mean facular contrast presented here. 相似文献
16.
We have derived the velocities of meridional flows by measuring the latitudinal motions (or drifts) of umbrae of spot groups
classified into three categories of area: 0 – 5 μ, 5 – 10 μ, and >10 μ (μ area in millionths of the solar hemisphere). The latitudinal drifts (or the meridional flows) in all three categories are
directed equatorward in both the northern and southern hemispheres. By sorting the spot groups into three area classes, we
are able to relate the respective latitudinal drifts with the three depths in the convection zone where the footpoints of
the flux loops of the spot groups of each area class are anchored. We obtain estimates of the anchor depths through a comparison
of the rotation rates of the spot groups of each area class with the rotation-rate profiles from helioseismic inversions.
The equatorward drifts obtained provide estimates of the meridional flows at the three depths in the convection zone and thereby
suggest the presence of return meridional flows as envisaged in the flux-transport dynamo models, which have remained undetected
so far. The data sources for this study are measurements of positions and areas of umbrae of sunspots from the photographic
white-light images of the Sun of the Kodaikanal Observatory archives for the period 1906 – 1987 and a very similar, but independent,
data set from the Mt. Wilson Observatory archives for the period 1917 – 1985. 相似文献
17.
We consider sterile neutrinos as a component of dark matter in the Milky Way and clusters, and compare their rest mass, decay
rate and the mixing angle. A radiative decaying rate of order Γ∼10−19 s−1 for sterile neutrino rest mass m
s
=18–19 keV can satisfactorily account for the cooling flow problem and heating source in Milky Way center simultaneously.
Also, these ranges of decay rate and rest mass match the prediction of the mixing angle sin 22θ∼10−3 with a low reheating temperature in the inflation model, which enables the sterile-active neutrino oscillation to be visible
in future experiments. However, decaying sterile neutrinos have to be ruled out as a major component of dark matter because
of the high decay rate. 相似文献
18.
The longitudinal distributions of the polar faculae, bright K Ca+ points, and sunspot areas have been investigated in three-year intervals at the minima and maxima of the last five solar cycles in the rotation system which corresponds to the background magnetic field:T = 27.23 days (Mikhailutsa, 1994b). It has been shown that there were three specific features of the polar faculae and bright K Ca+ point longitudinal distributions: (1) The longitudes of maxima and minima of the distributions were approximately the same in the last five solar cycles. (2) There were predominantly two opposite longitudinal maxima and two opposite longitudinal minima in the distributions of each hemisphere. (3) The distributions of the northern and southern hemispheres were in opposite phase. The extremes of the sunspot area longitudinal distributions were preferentially between the longitudes of the polar facular extremes. The period of the sector structure rotation was defined more precisely:T = 27.227 ± 0.003 days. The results found can serve as an indication that there is a global foursector structure seated in the solar interior which plays a visible role in the polar facular and sunspot distributions. 相似文献
19.
20.
For z = 0.8–2.2 redshift interval, quasar pair correlation function parameters and β redshift space distortion parameter (connected
to large-scale potential flows) values are estimated. We base them on the Main QSO Sample from SDSS Data Release 5. Standard
correlation function form ξ(r) = (r
0/r)γ is used for comoving distances r = 2–50 Mpc between quasars. We fix the parameters of the cosmological model: ΩΛ = 1 − Ω
M
= 0.726 and H
0 = 70.5 km/(s Mpc). We come to the best-fit parameter values of γ = 1.77 ± 0.20, r
0 = 5.52 ± 0.95 Mpc/h for r in the range 2–30 Mpc, γ = 1.91 ± 0.11, r
0 = 5.82 ± 0.61 Mpc for r in the range 2–50 Mpc. The mean β value is β = 0.43 ± 0.22. 相似文献