共查询到20条相似文献，搜索用时 484 毫秒
1.
A time series of Caii K filtergrams of the chromosphere was used to study the relationship between correlation lifetimes and autocorrelation length scales. The form of the lifetime-scale relation is inferred by comparing the distribution of the two parameters. A linear dependence of lifetime on cell area, with a least squares fit slope of 3.34×107 km2 hr–1, is deduced. The relation can be explained by assuming the network evolves by means of a diffusion process of the magnetic elements. 相似文献
2.
High-resolution H filtergrams and deep magnetograms were obtained from the Big Bear Solar Observatory (BBSO) and Huairou Solar Observation Station (HSOS) during 17–24 October 1997. The three days (17, 18, and 19) with the best image quality were selected for this initial research. We have found that macrospicules are triggered by interaction either between intranetwork and network elements or among several network magnetic elements. We present a model to explain the spatial relationship between macrospicules and magnetic fields. 相似文献
3.
Using high-resolution observations of deep magnetograms and H filtergrams obtained at Big Bear Solar Observatory during 17–24 October 1997, we have studied the interaction of intranetwork and network elements. The relationship between small-scale magnetic fields and active phenomena is investigated. Most of the small-scale active phenomena are triggered by the interaction either between intranetwork and network magnetic elements or among several network elements. The energy released due to the interaction of intranetwork–network elements and network–network elements is large enough to heat the corona. 相似文献
4.
The length scale and life time of the transition region network cells were studied using Heii 304 filtergrams. The temporal structure function was calculated from spatially aligned Heii 304 images. The estimated life time of the network cell was about 27 hr. We compared this life time with the life time of photospheric magnetic network and of the extrapolated magnetic network. The spatial structure function was calculated from the Heii 304 filtergrams. The calculated spatial structure function saturates at 25000 km. The transition region network elements are bigger in size than the photospheric magnetic network element. The magnetic network element equals the size of the Heii 304 network element when the photospheric magnetic field is extrapolated to a height of 3000 km above the photosphere where the magnetic fluxes are deployed. The derived value of the diffusion speed of the network elements was 0.098 km s–1. 相似文献
5.
The dependence of solar rotation on the size of the chromospheric tracers is considered. On the basis of an analysis of Ca ii K3 daily filtergrams taken in the period 8 May–14 August, 1972, chromospheric features can be divided into two classes according to their size. Features with size falling into the range 24 000–110 000 km can be identified with network elements, while those falling into the range 120 000–300 000 km with active regions, or brightness features of comparable size present at high latitudes. The rotation rate is determined separately for the two families of chromospheric features by means of a cross-correlation technique which directly yields the average daily displacement of tracers due to rotation. Before computing the cross-correlation functions, chromospheric brightness data have been filtered with appropriate bandpass and highpass filters for separating spatial periodicities whose wavelengths fall into the two ranges of size, characteristic of the network pattern and of the activity centers. A difference less than 1% of the rotation rate of the two families of chromospheric features has been found. This is an indication for a substantial corotation at chromospheric levels of different short-lived features, both related to solar activity and controlled by the convective supergranular motions. 相似文献
6.
B.N. Handy M.E. Bruner T.D. Tarbell A.M. Title C.J. Wolfson M.J. Laforge J.J. Oliver 《Solar physics》1998,183(1):29-43
The Transition Region and Coronal Explorer is a space-borne solar telescope featuring high spatial and temporal resolution. TRACE images emission from solar plasmas in three extreme-ultraviolet (EUV) wavelengths and several ultraviolet (UV) wavelengths, covering selected ion temperatures from 6000 K to 1 MK. The TRACE UV channel employs special optics to collect high-resolution solar images of the H i L line at 1216 Å, the C iv resonance doublet at 1548 and 1550 Å, the UV continuum near 1550 Å, and also a white-light image covering the spectrum from 2000–8000 Å.We present an analytical technique for creating photometrically accurate images of the C iv resonance lines from the data products collected by the TRACE UV channel. We use solar spectra from several space-borne instruments to represent a variety of solar conditions ranging from quiet Sun to active regions to derive a method, using a linear combination of filtered UV images, to generate an image of solar C iv 1550 Å emission. Systematic and statistical error estimates are also presented. This work indicates that C iv measurements will be reliable for intensities greater than 1014 photons s–1 cm–2 sr–1. This suggests that C iv 1550 Å images will be feasible with statistical error below 20% in the magnetic network, bright points, active regions, flares and other features bright in C iv. Below this intensity the derived image is dominated by systematic error and read noise from the CCD. 相似文献
7.
To study the evolution of large convective cells known as supergranules, a solar telescope was set up at Maitri, Indian permanent station in Antarctica region, during the local summer months (December 1989 through March 1990). A continuous sequence of calcium K-line filtergrams for 106 hours spaced at intervals of about 10 min was obtained. The analysis of the data indicates that the most probable lifetime of the calcium-K network is about 22 hours. The lifetime depends upon the size of the cell and is larger for bigger cells. The data also show that cells (of a given size) associated with remnant magnetic field regions live longer than those in the field-free region. This may mean that the magnetic field plays an important role in the confinement of these structures. 相似文献
8.
A helical surge (S 72, W 90) was recorded by a monochromatic filter at the University Observatory of Istanbul. It is a significient one at a very high latitude and without any center of activity. A sequence of the filtergrams showed some condensed points from which the motions of the plasma are traced. Different velocities were determined on each of the branches of the helical surge during its evolution. The surge reached its maximum height of 298 000 km and the maximum velocity of this upper region was 250 km s–1. 相似文献
9.
The evolution of the velocity and magnetic fields associated with supergranulation has been investigated using the Sacramento Peak Observatory Diode Array Magnetograph. The observations consist of time sequences of simultaneous velocity, magnetic field, and chromospheric network measurements. From these data it appears that the supergranular velocity cells may have lifetimes in excess of the accepted value of 24 hours. Magnetic field motions associated with supergranulation were infrequent and seem to be accompanied by changes in the velocity field. More prevalent were the slow dissipation and diffusion of stationary flux points. Vertical velocity fields of 200 m s–1 appear to be confined to downflows in magnetic field regions at supergranular boundaries. These downflows are only observed using certain absorption lines. Corresponding upflows in the center of supergranules of less than 50 m s–1 may be present but cannot be confirmed. 相似文献
10.
The kinematics of a loop system has been studied from high resolution Ca ii K line spectra and H filtergrams recorded at Oslo Solar Observatory.Emission features are seen to fall at supersonic velocities from the top of the arches towards the chromosphere. Our data are in agreement with the assumption of matter falling freely along a dipole type magnetic field of maximum height 100–150 thousand km. There is a slight asymmetry between positive and negative line shifts which can be accounted for as a tilt of the individual loops relative to the plane of the sky of 5–10°. The planes of the loops are also inclined by a small angle of approximately 15°. It appears that matter starts from rest at the top of the loops. An observed tilt of some emission features in the K line spectra may be explained by a gradient in the line-of-sight velocity with height caused by the curvature of the dipole type loops. 相似文献
11.
The apparent angles of more than 5000 quiet region spicules situated at various position angles around the Sun's limb have been measured on off-band H filtergrams taken during the years 1972–1975. The counts were made exclusively in projection on the disk, within 5–25° of the limb. The tendency of the average spicule to lean towards or away from the pole is small at most, and at no latitude exceeds 8°. The spread in angles is 30–35°. 相似文献
12.
K. A. Marsh 《Solar physics》1976,50(1):37-48
A detailed study has been made of the lifetimes and evolution of fibrils in McMath 12417, using high resolution filtergrams in H and Ca ii K made at Big Bear Solar Observatory. It was found that when viewed near disk centre, the lifetime of a fibril is a monotonically increasing function of its maximum apparent length. This relationship, together with the form of the variation of fibril lengths as a function of time, suggests that fibrils result from material being impulsively injected into magnetic field lines at approximately 30 km s–, and returning under gravity. The lifetimes and apparent lengths of fibrils are then a function of the inclination of the field lines only. A study of wavelength scans through the H line confirms that the apparent extension and retraction of fibrils represents true mass motion. 相似文献
13.
Large-scale active coronal phenomena in Yohkoh SXT images 总被引：1，自引：0，他引：1
Zdenk vestka Frantiek Fárník Hugh S. Hudson Yutaka Uchida Paul Hick James R. Lemen 《Solar physics》1995,161(2):331-363
We have found several occurrences of slowly rising giant arches inYohkoh images. These are similar to the giant post-flare arches previously discovered by SMM instruments in the 80s. However, we see them now with 3–5 times better spatial resolution and can recognize well their loop-like structure. As a rule, these arches followeruptive flares with gradual soft X-ray bursts, and rise with speeds of 1.1–2.4 km s–1 which keep constant for >5 to 24 hours, reaching altitudes up to 250 000 km above the solar limb. These arches differ from post-flare loop systems by their (much higher) altitudes, (much longer) lifetimes, and (constant) speed of growth. One event appears to be a rise of a transequatorial interconnecting loop.In the event of 21–22 February 1992 one can see both the loop system, rising with a gradually decreasing speed to an altitude of 120 000 km, and the arch, emerging from behind the loops and continuing to rise with a constant speed for many more hours up to 240 000 km above the solar limb. In the event of 2–3 November 1991 three subsequent rising large-scale coronal systems can be recognized: first a fast one with speed increasing with altitude and ceasing to be visible at about 300 000 km. This most probably shows the X-ray signature of a coronal mass ejection (CME). A second one, with gradually decreasing speed, might represent very high rising flare loops. A third one continues to rise slowly with a constant speed up to 230 000 km (and up to 285 000 km after the speed begins to decay), and this is the giant arch. This event, including an arch revival on November 4–5, is very similar to rising giant arches observed by the SMM on 6–7 November 1980. Other events of this kind were observed on 27–28 April 1992, 15 March 1993, and 4–6 November 1993, all seen above the solar limb, where it is much easier to identify them.The temperature in the brightest part of the arch of 2–3 November 1991 was increasing with its altitude, from 2 to 4 × 106 K, which seems to be an effect of slower cooling at lower densities. Under an assumption of line-of-sight thickness of 50 000 km, the emission measure indicates densities from 1.1 × 1010 cm–3 at an altitude of 150 000 km to 1.0 × 109 cm–3 at 245 000 km 11.5 hours later. It appears that the arch is composed of plasma of widely different temperatures, and that hot plasma rises faster than the cool component. Thus the whole arch expands upward, and its density gradient increases with time, which explains whyYohkoh images show only the lowest and coolest parts of the expanding structure. The whole arch may represent an energy in excess of 1031 erg, and more if conduction contributes to the arch cooling.We suggest that the rise of the arch is initiated by a CME which removes the magnetic field and plasma in the upper corona, and the coronal structures remaining below this cavity begin to expand into the vacuum left behind the CME. However, we are unable to explain why the speed of rise stays constant for so many hours. 相似文献
14.
We extract a temporal sequence of the 1355 UT 4 July, 1974 event from monochromatic filtergrams in Na light obtained in Rome on the McMath region No. 13043-July 1974. It is, to our knowledge, the first temporal sequence of a flare seen through a narrow-band filter (80 mÅ) in the Na-D lines. Due to the properties of Na filtergrams we could also derive quite easily the exact relative position among sunspots, magnetic fields and flare-knots. The last result is indeed a very useful tool when studying an active region. For the McMath No. 13043 we were able to infer some interesting remarks about the magnetic pattern at the flaring site. 相似文献
15.
We report the first detection of molecular hydrogen emission in the vicinity of a Wolf-Rayet star and nebula. The spatial distribution of the excited molecular gas is filamentary and is not correlated with the distribution of the ionised gas as traced by optical emission lines. The typical H2 surface brightness in the filaments is 5× 10–5 ergs s–1 cm–2 str–1. We demonstrate that the excitation mechanism can be shocks or fluorescence from the strong ultraviolet flux of the WR star. 相似文献
16.
M. Berge-Nguyen A. Cazenave A. Lombard W. Llovel J. Viarre J.F. Cretaux 《Global and Planetary Change》2008,62(1-2):1-13
This study investigates past sea level reconstruction (over 1950–2003) based on tide gauge records and EOF spatial patterns from different 2-D fields. In a first step, we test the influence on the reconstructed signal of the 2-D fields temporal coverage. For that purpose we use global grids of thermosteric sea level data, available over 1950–2003. Different time spans (in the range 10–50 yr) for the EOF spatial patterns, and different geographical distributions for the 1-D thermosteric sea level time series (interpolated at specific locations from the 2-D grids), are successively used to reconstruct the 54-year long thermosteric sea level signal. In each case we compare the reconstructed trend map with the reference. The simulation indicates that the longer the time span covered by the spatial EOFs, the closer to the reference the reconstructed thermosteric sea level trends. In a second step, we apply the method to reconstructing 2-D sea level data over 1950–2003, combining sparse tide gauge records available since 1950, with EOF spatial patterns from different sources: (1) thermosteric sea level grids over 1955–2003, (2) sea level grids from Topex/Poseidon satellite altimetry over 1993–2003, and (3) dynamic height grids from the SODA reanalysis over 1958–2001. The reconstructed global mean sea level trend based on thermosteric EOFs (case 1) is significantly lower than the observed trend, while the interannual/decadal sea level fluctuations are well reproduced. Case 2 (Topex/Poseidon EOFs over 1993–2003) leads to a global mean sea level trend over the 54-year time interval very close to the observed trend. But the spatial trends of the reconstruction over 1950–2003 are significantly different from those obtained with thermosteric EOFs. Case 3 (SODA EOFs over 1958–2001) provides a reconstruction trend map over 1950–2003 that differs significantly from the previous two cases. We discuss possible causes for such differences. For the three cases, on the other hand, reconstructed spatial trends over 1993–2003 agree well with the regional sea level trends observed by Topex/Poseidon. 相似文献
17.
Stephen W. Prata 《Solar physics》1973,33(1):119-130
Centerline H filtergrams providing nearly full day coverage of the Sun are used to study the lifetimes of enhanced network features near active regions. In the two cases studied the fraction remaining of those features present at an original epoch remains near unity for 50 h, then drops exponentially with a 1/e decay time of 30 h. Histories of representative enhanced network features are discussed. 相似文献
18.
In this paper we carry out an analysis of the spatial–temporal line-of-sight velocity variations measured in the chromospheric (H, H) and photospheric (Fei 6569 Å, Fei 4864 Å, Nii 4857 Å) lines at the base of 17 coronal holes. Time series of a duration from 43 to 120 min were recorded with the CCD line-array and the CCD matrix. Rather frequently we observed quasi-stationary upward flows with a measured velocity of up to 1 km s–1 in the photosphere and up to 4–5 km s–1 in the chromosphere (equivalent radial velocity of up to 3 km s–1 and up to 12–15 km s–1 accordingly) near dark points on the chromospheric network boundary inside polar CH. Line-of-sight velocity fluctuation spectra contain meaningful maxima in the low-frequency region clustering around the values 0.4, 0.75, and 1 mHz. Usually, the spatial localization of these maxima mutually coincides and, in our opinion, coincides with the chromospheric network boundary. Acoustic 3- and 5-min oscillations are enhanced in the coronal hole region and reach 1 km s–1 in the photosphere and 3–4 km s–1 in the chromosphere. These oscillations are not localized spatially and are distinguished throughout the entire region observed. 相似文献
19.
We studied quantitatively the relation between the intensity of Caii K-line bright features and the intensity of the associated magnetic elements using two data sets obtained at the Big Bear Solar Observatory. Both network and intranetwork (IN) structures were considered. Magnetic field changes always affected the K-line emission; for example, the appearance of new bipoles was always followed by enhanced K-line emission. There is an almost linear correlation between the K-line intensity and the magnetic field strength of the stronger network elements (elements with absolute field strength higher than 11–19.5 G). We identified two classes of intranetwork K-line elements: magnetic and non-magnetic ones. The number of the magnetic K-line IN elements above a 1-sigma threshold was only 5%–10% of the number of the non-magnetic ones. The magnetic K-line IN elements were almost 3 to 4 times brighter compared to the non-magnetic elements. On the other hand, the non-magnetic elements were moving with typical velocities of 35–40 km s–1 while the velocities of the magnetic K-line elements were of the order of 1 km s–1. 相似文献
20.
An occultation of X-ray emission from a solar flare occurred during the eclipse of 7 March, 1970 and was observed by an NRL instrument aboard the OSO-5 satellite. Ionization chamber photometers covering the wavelength ranges 0.5–3 Å, 1–8 Å, and 8–16 Å provided flux measurements once every 15 s providing a spatial resolution of 20 arc sec at the solar surface. Within this limitation the X-ray flare was observed to be confined within a region 136 000 km in one dimension.However, the measurements indicate the existence of a denser core 54 000 km wide in the direction of advance of the Moon's limb. Comparison of these results with X-ray photographs of flare regions are made and a model for the development of the soft X-ray flare is proposed. 相似文献