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1.
O. Engvold 《Solar physics》1970,11(2):183-197
Absorption band spectra of BH and BO have been searched for and not found in spectra of sunspots.Electronic oscillator strengths are available only for the A
1
-X
1
+ system of the BH molecule. The absence of the (0,0) band of BH at 4332 Å reflects a solar abundance of boron logA
B<2.5.The band spectra of BN are several orders of magnitude weaker in sunspots than those of BH and BO.Kitt Peak National Observatory Contribution No. 488.Visiting Astronomer, Solar Division, Kitt Peak National Observatory - Operated by The Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
2.
Muthu Priyal Jagdev Singh Ravindra Belur Somasundaram Kameshwaran Rathina 《Solar physics》2017,292(7):85
In our previous article (Priyal et al. in Solar Phys. 289, 127, 2014) we have discussed the details of observations and methodology adopted to analyze the Ca-K spectroheliograms obtained at the Kodaikanal Observatory (KO) to study the variation of Ca-K plage areas, enhanced network (EN), and active network (AN) for Solar Cycles, namely 19, 20, and 21. Now, we have derived the areas of chromospheric features using KO Ca-K spectroheliograms to study the long-term variations of Solar Cycles 14 to 21. The comparison of the derived plage areas from the data obtained at the KO observatory for the period 1906?–?1985 with that of MWO, NSO for the period 1965?–?2002, earlier measurements made by Tlatov, Pevtsov, and Singh (Solar Phys. 255, 239, 2009) for KO data, and the SIDC sunspot numbers shows a good correlation. The uniformity of the data obtained with the same instrument remaining with the same specifications provided a unique opportunity to study long-term intensity variations in plages and network regions. Therefore, we have investigated the variation of the intensity contrast of these features with time at a temporal resolution of six months assuming that the quiet-background chromosphere remains unchanged during the period 1906?–?2005 and found that the average intensity of the AN, representing the changes in small-scale activity over solar surface, varies with solar cycle being less during the minimum phase. In addition, the average intensity of plages and EN varies with a very long period having a maximum value during Solar Cycle 19, which was the strongest solar cycle of twentieth century. 相似文献
3.
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
4.
Long-lived (>20 days) sunspot groups extracted from the Greenwich Photoheliographic Results (GPR) are examined for evidence of decadal change. The problem of identifying sunspot groups that are observed on consecutive solar rotations (recurrent sunspot groups) is tackled by first constructing manually an example dataset of recurrent sunspot groups and then using machine learning to generalise this subset to the whole GPR. The resulting dataset of recurrent sunspot groups is verified against previous work by A. Maunder and other Royal Greenwich Observatory (RGO) compilers. Recurrent groups are found to exhibit a slightly larger value for the Gnevyshev?–?Waldmeier Relationship than the value found by Petrovay and van Driel-Gesztelyi (Solar Phys. 51, 25, 1977), who used recurrence data from the Debrecen Photoheliographic Results. Evidence for sunspot-group lifetime change over the previous century is observed within recurrent groups. A lifetime increase of a factor of 1.4 between 1915 and 1940 is found, which closely agrees with results from Blanter et al. (Solar Phys. 237, 329, 2006). Furthermore, this increase is found to exist over a longer period (1915 to 1950) than previously thought and provisional evidence is found for a decline between 1950 and 1965. Possible applications of machine-learning procedures to the analysis of historical sunspot observations, the determination of the magnetic topology of the solar corona and the incidence of severe space–weather events are outlined briefly. 相似文献
5.
A Multi-Application Solar Telescope (MAST) is proposed to be installed at the lake site (Lake Fatehsagar) of Udaipur Solar Observatory (USO) in India. The lake site Observatory of USO is located on a small island in the middle of the lake. To determine the optimum size of the MAST (for use with an adaptive optics system), it was decided to quantify the seeing conditions prevailing at the lake site during the different months of the year. For this purpose, we have used short-exposure (3 ms) high-resolution Hα (6563 Å) images (spatial scale of ～0.55 arc sec per pixel) of the Sun taken in burst mode with the 15-cm refractor Spar telescope located at the lake site of USO. Spectral ratio technique as reported by von der Lühe (1984, J. Opt. Soc. Am. A1, 510) has been used to estimate the Fried’s parameter (r 0) at this site, which gives the quantitative measure of astronomical seeing. This study has been carried out daily on an hourly basis during 4:30?–?10:30 UT over the months January?–?June of the years 2005 and 2006 to understand the diurnal and seasonal variations in r 0 at this site. It is noteworthy that the lake was almost dry during the observing period in 2005, while it overflowed during our observations in 2006 because of abundant monsoon rains. The seeing in the presence of water shows improvement in r 0 by about 1.0 cm with respect to the previous year’s dry condition and mean r 0 varies between 4.0 and 4.5 cm as evident from the data obtained between January and June, 2006. 相似文献
6.
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
7.
Yngve Öhman 《Solar physics》1969,10(1):178-183
During a stay at the Kitt Peak National Observatory the writer has tried to find an influence of flare radiation on the high photospheric and low chromospheric lines of the area occupied by the flare. Observations have been made in the H region and in the region of the H and K lines. When flare emission is present in sunspots some of the faint (molecular) lines seem to be weakened. When a flare appears near the solar limb some of the Evershed-type (chromospheric) lines are strongly influenced.Kitt Peak National Observatory Contribution No. 481.Visiting Astronomer to the Solar Division, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation. 相似文献
8.
Trans-equatorial loops (TLs) are one of the distinct magnetic structures in the solar corona and have a close relationship to solar activity. We present a systematic study of the origin of TLs linking with the Babcock?–?Leighton dynamo process based on the model of Chatterjee, Nandy, and Choudhuri (Astron. Astrophys. 427, 1019, 2004). We propose that TLs are visible signatures of poloidal field lines across the equator. The cycle variation of TL lengths obtained by the connectivities of poloidal field lines happens to be roughly in agreement with what one gets by considering the positions of sunspots. This explains why this cycle variation of TL lengths was found to be in conformity with Spörer’s law. The active regions always make the poloidal field configuration favorable to form TLs, which causes the conformity. The formation of TLs is a three-dimensional problem, which will require three-dimensional dynamo models for full investigation. 相似文献
9.
V. M. S. Carrasco J. M. Vaquero M. C. Gallego A. Lourenço T. Barata J. M. Fernandes 《Solar physics》2018,293(11):153
A sunspot catalogue was published by the Coimbra Astronomical Observatory (Portugal), which is now called the Geophysical and Astronomical Observatory of the University of Coimbra, for the period 1929?–?1941. We digitalised data included in that catalogue and provide a machine-readable version. We show the reconstructions for the (total and hemispheric) sunspot number index and sunspot area according to this catalogue and compare it with the sunspot number index (version 2) and the Balmaceda sunspot area series (Balmaceda et al. in J. Geophys. Res.114, A07104, 2009). Moreover, we also compared the Coimbra catalogue with records made at the Royal Greenwich Observatory. The results demonstrate that the historical catalogue compiled by the Coimbra Astronomical Observatory contains reliable sunspot data and can therefore be considered for studies about solar activity. 相似文献
10.
As the observational signature of the footprints of solar magnetic field lines open into the heliosphere, coronal holes provide a critical measure of the structure and evolution of these lines. Using a combination of Solar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope (SOHO/EIT), Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), and Solar Terrestrial Relations Observatory/Extreme Ultraviolet Imager (STEREO/EUVI A/B) extreme ultraviolet (EUV) observations spanning 1996?–?2015 (nearly two solar cycles), coronal holes are automatically detected and characterized. Coronal hole area distributions show distinct behavior in latitude, defining the domain of polar and low-latitude coronal holes. The northern and southern polar regions show a clear asymmetry, with a lag between hemispheres in the appearance and disappearance of polar coronal holes. 相似文献
11.
Spectra of several strong lines of sunspots have been obtained with the Echelle spectrograph at the Vacuum Tower Telescope, Sacramento Peak Observatory. With a variety of model atmospheres, Ca ii H, K, and 18498 line profiles were calculated using a non-LTE line formation procedure.In the present study we examined only a specific part of the sunspot umbra which is thought to be coolest over the spot. An optimum model representing such a region is presented and its physical properties are discussed.This work has been supported by the U.S. - Republic of Korea Cooperative Science Program (K-24). 相似文献
12.
The expected equivalent widths of individual rotational lines of the most intense Q
2 branch of the 0-0 band of the A
2-X2i; system of S32H and S34H have been calculated in the umbral spectrum for five disk positions using Zwaan's (1974) sunspot model. Percentage abundance of S34 in the terrestrial case has been considered valid in our calculations.Strong lines of S32H and S34H of the A-X band system should be detectable in the sunspot spectrum. The molecule SH may play a possible role as a major opacity source in the ultraviolet spectrum of sunspots along with the molecule OH in the upper layers (up to
0.5m = 1.0) wherefrom most of the continuum arises. Study of this molecule in the umbral spectrum may also provide the solar isotopic abundance ratio N(S32)/N(S34). 相似文献
13.
N. Alonizan R. Qindeel N. Ben Nessib S. Sahal-Bréchot Milan S. Dimitrijević 《Journal of Astrophysics and Astronomy》2015,36(4)
Stark broadening parameters for nine neutral oxygen (O I) lines have been determined within the impact approximation and the semiclassical perturbation method. The atomic data have been taken from the TOPbase and NIST atomic databases. The electron and proton Stark widths and shifts and ion broadening parameter values for these O I lines have been calculated for electron density of 10 16 cm ?3 and for 4 different electron temperatures in the range of 5000 K to 40000 K. These Stark broadening parameters are compared with our previous results (Ben Nessib, N. et al. 1996, Physica Scripta, 54, 603–613), where we calculated Stark broadening parameters for only four O I spectral lines and where Stark widths and shifts were compared with experimental and theoretical data available in the literature. In the present paper, we have also compared our results with the Griem’s book (Griem, H. R. 1974, Spectral line broadening by plasmas) and VALD (Ryabchikova, T. et al. 2015, Physica Scripta, 90, 054005) values. 相似文献
14.
P. Sriramachandran R. Shanmugavel S. P. Bagare N. Rajamanickam 《Astrophysics and Space Science》2009,323(1):41-49
A high resolution spectrum of a sunspot umbra is used for identification of rotational lines due to (0, 0) band of the A
2Π–X
2Σ+ system and (0, 0), (1, 1), and (2, 2) bands of the B
2Σ+–X
2Σ+ system of the molecule SrF. The published sunspot umbral spectrum obtained with Fourier Transform Spectrometer and solar
telescope of National Solar Observatory/National Optical Astronomy Observatory at Kitt Peak was used for the study. The new
identification of more than 200 SrF lines in the umbral spectrum confirms that this molecule accounts for the majority of
lines in the spectral range 15050 to 15360 cm−1 and 17240 to 17300 cm−1. Equivalent widths have been measured for well-resolved lines of these bands and the effective rotational temperatures have
been estimated for which the presence is confirmed. 相似文献
15.
Leonid Didkovsky 《Solar physics》2018,293(6):87
Some quiet-Sun days observed by the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO) during the time interval in 2010?–?2017 were used to continue our previous analyses reported by Didkovsky and Gurman (Solar Phys.289, 153, 2014a) and Didkovsky, Wieman, and Korogodina (Solar Phys.292, 32, 2017). The analysis consists of determining and comparing spatial spectral ratios (spectral densities over some time interval) from spatial (segmentation-cell length) power spectra. The ratios were compared using modeled compatible spatial frequencies for spectra from the Extreme ultraviolet Imaging Telescope (EIT) on-board the Solar and Heliospheric Observatory (SOHO) and from AIA images. With the new AIA data added to the EIT data we analyzed previously, the whole time interval from 1996 to 2017 reported here is approximately the length of two “standard” solar cycles (SC). The spectral ratios of segmentation-cell dimension structures show a significant and steady increase with no detected indication of SC-related returns to the values that characterize the SC minima. This increase in spatial power at high spatial frequencies is interpreted as a dissipation of medium-size EUV network structures to smaller-size structures in the transition region. Each of the latest ratio changes for 2010 through 2017 spectra calculated for a number of consecutive short-term intervals has been converted into monthly mean ratio (MMR) changes. The MMR values demonstrate variable sign and magnitudes, thus confirming the solar nature of the changes. These changes do not follow a “typical” trend of instrumental degradation or a long-term activity profile from the He?ii (30.4 nm) irradiance measured by the Extreme ultraviolet Spectrophotometer (ESP) either. The ESP is a channel of the Extreme ultraviolet Variability Experiment (EVE) on-board SDO. 相似文献
16.
V. Bumba 《Solar physics》1967,1(3-4):371-376
Preliminary results of magnetic field measurements in small sunspots from spectrograms obtained with the aid of the McMath Solar Telescope at the Kitt Peak National Observatory are presented. The measured intensities are greater than or equal to about 1200 Gauss. Furthermore, a broadening of the Fei line 6302.508 Å was found in some places of intergranular space. The importance of intergranular space as a possible potential earliest stage of sunspot development is mentioned.Kitt Peak National Observatory, Contribution No. 222.Visiting Astronomer, 1964, Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the Nat. Science Foundation. 相似文献
17.
Franca Chiuderi-Drago Rino Bandiera Roberto Falciani Ester Antonucci Kenneth R. Lang Robert F. Willson Cornelis Slottje 《Solar physics》1982,80(1):71-85
The Solar Maximum Mission Satellite, the Sacramento Peak Vacuum Tower Telescope, the Very Large Array and the Westerbork Synthesis Radio Telescope have been used to observe active region AR 2490 on two consecutive days at soft X-ray, ultraviolet, optical and radio wavelengths (2, 6, and 20 cm), with comparable angular resolution (2 to 15) and field of view (4 × 4). The radio emissions at = 6 cm and 20 cm show a double structure in which one component is associated with bright H plage, C iv and soft X-ray emission, and the other component is associated only with sunspots. No radiation at = 2 cm is detected in this latter component. Coronal temperature and emission measure derived from X-ray lines indicate that the dominant radiation mechanism of the plage-associated component is due to thermal bremsstrahlung while the gyroresonance absorption coefficient must be invoked to account for the high brightness temperature (T
b
2×106K) observed in the sunspot associated component. The high magnetic field strength needed (600 G at a level where T2×106K) is explained assuming a thin transition zone, in order to reach a high electron temperature close to the sunspot, where the magnetic fields are stronger. A higher temperature gradient above sunspots is also consistent with the absence of detectable C iv emission.Cooperative study of the SMY-FBS Project.On leave from the University of Napoli.On leave from the University of Torino.On sabbatical leave 1980–81 at the Arcetri Observatory.On leave from Toyokawa Observatory, Japan. 相似文献
18.
In our previous articles (Chertok et al. in Solar Phys. 282, 175, 2013; Chertok et al. in Solar Phys. 290, 627, 2015), we presented a preliminary tool for the early diagnostics of the geoeffectiveness of solar eruptions based on the estimate of the total unsigned line-of-sight photospheric magnetic flux in accompanying extreme ultraviolet (EUV) arcades and dimmings. This tool was based on the analysis of eruptions observed during 1996?–?2005 with the Extreme-ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). Empirical relationships were obtained to estimate the probable importance of upcoming space weather disturbances caused by an eruption, which just occurred, without data on the associated coronal mass ejections. In particular, it was possible to estimate the intensity of a non-recurrent geomagnetic storm (GMS) and Forbush decrease (FD), as well as their onset and peak times. After 2010?–?2011, data on solar eruptions are obtained with the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We use relatively short intervals of overlapping EIT–AIA and MDI–HMI detailed observations, and additionally, a number of large eruptions over the next five years with the 12-hour cadence EIT images to adapt the SOHO diagnostic tool to SDO data. We show that the adopted brightness thresholds select practically the same areas of arcades and dimmings from the EIT 195 Å and AIA 193 Å image, with a cross-calibration factor of 3.6?–?5.8 (5.0?–?8.2) for the AIA exposure time of 2.0 s (2.9 s). We also find that for the same photospheric areas, the MDI line-of-sight magnetic flux systematically exceeds the HMI flux by a factor of 1.4. Based on these results, the empirical diagnostic relationships obtained from SOHO data are adjusted to SDO instruments. Examples of a post-diagnostics based on SDO data are presented. As before, the tool is applicable to non-recurrent GMSs and FDs caused by nearly central eruptions from active regions, provided that the southern component of the interplanetary magnetic field near the Earth is predominantly negative, which is not predicted by this tool. 相似文献
19.
Hyungmin Park Jongchul Chae Donguk Song Ram Ajor Maurya Heesu Yang Young-Deuk Park Bi-Ho Jang Jakyoung Nah Kyung-Suk Cho Yeon-Han Kim Kwangsu Ahn Wenda Cao Philip R. Goode 《Solar physics》2013,288(1):105-116
We observed solar prominences with the Fast Imaging Solar Spectrograph (FISS) at the Big Bear Solar Observatory on 30 June 2010 and 15 August 2011. To determine the temperature of the prominence material, we applied a nonlinear least-squares fitting of the radiative transfer model. From the Doppler broadening of the Hα and Ca ii lines, we determined the temperature and nonthermal velocity separately. The ranges of temperature and nonthermal velocity were 4000?–?20?000 K and 4?–?11 km?s?1. We also found that the temperature varied much from point to point within one prominence. 相似文献