共查询到20条相似文献，搜索用时 15 毫秒
1.
G. A. Gurzadyan 《Astrophysics and Space Science》1977,48(2):313-334
An extensive analysis is made of the theory of flare stars based on the fast electron hypothesis, in the light of the latest observational evidence. It is shown that an adequate agreement of theory with the observations obtains regarding the internal regular features in the flare amplitude data inUBV rays, as well as the changes of the colour characteristics of stars during the flares; in the latter case the analysis is made not only in respect of the UV Cet-type stars, but flare stars as well, forming a part of the Orion association. Problems bearing on the negative flare and the screening effect are dealt with. New properties of the light curves of flares are revealed, based on the above theory.Particular emphasis is laid on the X-ray radiation from flare stars. It is shown that the observed spectrum of X-ray radiation of flare stars differs sharply from that of X-ray radiation both of the stellar corona and solar X-ray flares. At the same time, the observed X-ray spectrum of flares is in complete harmony with the previously calculated theoretical spectrum corresponding to nonthermal bremsstrahlung with the energy of monoenergetic fast electrons 1.5 MeV. The durations of X-ray flares should be essentially shorter than that of the optical flares. The very high momentary intensities of the X-ray brightness with the exceedingly small duration at the curve maximum is predicted. It is shown that the gamma-ray bursts recorded so far have no relation whatever to flare stars. 相似文献
2.
Beigman I. L. Grineva Yu. I. Mandel'stam S. L. Vainstein L. A. Žitnik I. A. 《Solar physics》1969,9(1):160-165
With the use of X-ray heliographs carried by the satellites Cosmos-166 and Cosmos-230 the height of an X-ray flare was found to be about 20–25 000 km. The regions of the X-ray flares possess a filamentary structure which, during the development of the flares, shows spatial changings with speeds up to 107 cm/sec. 相似文献
3.
Data from SSRT form the basis for initiating a study of the properties of long-lived, compact microwave sources located outside sunspots. A step-like birth of such a source was detected and is described in this study. This sheds light on the relationship between the step-like phenomenon detected with SSRT and the peculiar source phenomenon observed at RATAN-600. Peculiar sources precede large flares and are projected onto the photospheric neutral line. It seems likely that the build-up of a large flare is also step-like in character. We also discuss a source overlying the neutral line which accompanied a large active region that did not produce any large flare. 相似文献
4.
The active region NOAA 6555 had several locations of highly sheared magnetic field structure, yet, only one of them was the site for all the five X-class flares during its disk passage in March 1991. The pre-flare observations of high-resolution H filtergrams, vector magnetograms and H Dopplergrams of the 2B/X5.3 flare on 25 March 1991 show that the flaring site was characterized by a new rising emerging flux region (EFR) near the highly sheared magnetic field configuration. The polarity axis of the emerging flux was nearly perpendicular to the pre-existing magnetic neutral line. The location of the EFR was the site of initial brightening in H. The post-flare magnetograms show higher magnetic shear at the flare location compared to the post-flare magnetograms, which might indicate that the EFR was sheared at the time of its emergence. As the new EFR coincided with the occurrence of the flare, we suggest that it might have triggered the observed flare. Observations from Big Bear Solar Observatory and Marshall Space Flight Center also show that there was emergence of new flux at the same location prior to two other X-class flares. We find that out of five observed X-class flares in NOAA 6555, at least in three cases there are clear signatures of flare-related flux emergence. Therefore, it is concluded that EFRs might play an important role in destabilizing the observed sheared magnetic structures leading to large X-class flares of NOAA 6555. 相似文献
5.
P. A. Sturrock 《Solar physics》1972,23(2):438-443
On the assumption that solar flares are due to instabilities which occur in current sheets in the Sun's atmosphere, one may classify magnetic-field configurations associated with flares into two types. One is characterized by closed current sheets, magnetic-field lines adjacent to these sheets beginning and ending at the Sun's surface. The other is characterized by open current sheets, magnetic-field lines adjacent to these sheets beginning at the Sun's surface but extending out into interplanetary space. Flares associated with open current sheets can produce Type III radio bursts and high-energy-particle events, but flares associated with closed current sheets cannot. The flare of July 6, 1966 apparently consisted of one flare of each type. 相似文献
6.
Syun-Ichi Akasofu 《Astrophysics and Space Science》1985,108(1):81-93
In the past, both magnetospheric substorms and solar flares have almost exclusively been discussed in terms of explosive magnetic reconnection. Such a model may conceptually be illustrated by the so-called tippy-bucket model, which causes sudden unloading processes, namely a sudden (catastrophic, stochastic, and unpredictable) conversion of stored magnetic energy. However, recent observations indicate that magnetospheric substorms can be understood as a result of a directly driven process which can conceptually be illustrated by the pitcher model in which the output rate varies in harmony with the input rate. It is also possible that solar flare phenomena are directly driven by a photospheric dynamo. Thus, explosive magnetic reconnection may simply be an unworkable hypothesis and may not be a puzzle to be solved as the primary energy supply process for magnetospheric substorms and solar flares. 相似文献
7.
Using photospheric and H observations and total radio flux data we study a two-ribbon flare in AR NOAA 4263 which was a part of a flare event complex on July 31, 1983. We find some facts which illuminate the special way of flare triggering in the analysed event. Around a double spot the photospheric vector magnetic field is discussed with respect to the chromospheric activities. In one of the spots the feet of long stretched loops are pushed down under steepening loops rooted in the same spot. This causes energy build-up by twist and shear in the stretched loops. One foot of the two-ribbon flare (triggered in the stretched and underpushed loop system) roots in a part of the spot umbra and penumbra where the field runs in extremely flat like a pressed spiral spring. A strange radio event, starting before the flares, can be interpreted as a precursor activity of the flare event complex. The radio data support the view that the analyzed flare process and the given magnetic field structure, respectively, are not very effective in energetic particle generation and escape. 相似文献
8.
We show that the requirement of alocal conformal symmetry of the Abelian Higgs sunspot leads, at least formally, to a complex-valued electromagnetic potential, whose imaginary part is a conformal compensating potential. It is shown that there exists a fundamental difference between conformal and ordinary electromagnetic fields; whereas the ordinary total magnetic flux of a spot is quantized its conformal analogue has to vanish if the Higgs field is to be single-valued. We further stress that such a complex-valued Abelian Higgs field configuration mimics quite well, under certain conditions (all the salient features of) the classical Abelian Higgs sunspot. 相似文献
9.
K X-ray line emission from S, Ar, Ca and Fe is calculated for conditions likely to exist in solar flares. We consider both the non-thermal and thermal phases of flares as indicated by X-ray observations. Impulsive non-thermal events seen at the onset of a flare at photon energies > 20 keV generally give rise to small K line fluxes (<250 photons cm-2 s-1) on the basis of data presented by Kane and Anderson. The amount of S K radiation in particular depends sensitively on the lower-energy bound of the non-thermal electron distribution giving rise to the impulsive burst, offering a possible means of determining this. Thermal K emission is significant for only Fe ions. For S, Ar and Ca, the temperatures required for a sizeable number of electrons with energies greater than the K-ionization potential will also strip these elements to ionization stages too high for K transitions to be possible. Comparison of thermal K emission from iron during an intense solar flare leads to a very high emission measure on the basis of these calculations, but such a value seems to be compatible with an analysis of the 1–3 Å continuum during the same event.NAS/NRC Resident Research Associate.Visiting Scientist, High Altitude Observatory, NCAR, Boulder, Colo. 80302. 相似文献
10.
C. Martin Gaskell 《Astrophysics and Space Science》1982,82(1):247-248
The reported correlation between the absorption-line of emission-line redshifts of quasars is shown to be due to selection effects and thus to favour neither the intrinsic nor intervening hypotheses for the origin of quasar absorption lines. 相似文献
11.
Stephen Pintér 《Astrophysics and Space Science》1986,125(2):375-378
A mechanism explaining the generation of the helium-enriched plasma-condensation colud (HAE-events) behind the front of shock waves associated with mass-ejecting flares is presented. The mechanism is based on the occurence of physical conditions, analogous to those in a Wilson cloud chamber in a magnetic field, behind the front of a flare-generated shock wave propagation out into interplanetary space. Consequently, if the solar atmosphere above the flare active region is saturated with ejected helium plasma, conditions are created for the forming of the helium-enriched plasma-condensation colud in the temperature-depressed region behind the shock wave front. 相似文献
12.
E. W. Cliver 《Solar physics》1995,157(1-2):285-293
The evolution of solar flare nomenclature is reviewed in the context of the paradigm shift, in progress, from flares to coronal mass ejections (CMEs) in solar-terrestrial physics. Emphasis is placed on: the distinction between eruptive (Class II) flares and confined (Class I) flares; and the underlying similarity of eruptive flares inside (two-ribbon flares) and outside (flare-like brightenings accompanying disappearing filaments) of active regions. A list of research questions/problems raised, or brought into focus, by the new paradigm is suggested; in general, these questions bear on the interrelationships and associations of the two classes (or phases) of flares. Terms such as eruptive flare and eruption (defined to encompass both the CME and its associated eruptive flare) may be useful as nominal links between opposing viewpoints in the flares vs CMEs controversy. 相似文献
13.
Pierre Kaufmann 《Astrophysics and Space Science》1978,57(1):249-252
A number of suggestive coincidences are found in a purely speculative analogy between the by-products, of a minihole fast evaporation in a plasma, and by-products from flares at magnetospheres. Solar flares might serve as good examples. From an observational point of view our attention is drawn to the considerable extent of the blank time interval existing between known before and after evidences on flares, during which some exotic energy conversion processes could be invoked to explain the large amount of energy released in time-scales that might be very short. We suggest that fundamental progress in the knowledge of energy conversion, processes in flares require observational data with a time resolution several orders of magnitude, better than the currently available data, particularly, for hard X-rays. 相似文献
14.
Corrections are given which transform the Tables of the solar radiation data (Labs and Neckel, 1968) into the International Practical Temperature Scale of 1968. Additionally, for the adjustment of the data of the true continuum and the corresponding line blanketing as well, the veiled line effect mentioned first by Carbon et al. (1968), but studied in more detail by Holweger (1970a), has been considered also.The corresponding corrections of the solar irradiance result in an improved value of the spectrophotometric solar constant: S = 1.947 cal cm-2 min-1 or 0.1358 W cm-2. Two Tables presenting the highest (window-) intensities and the corrected irradiance data have been added. 相似文献
15.
Robert M. Wilson 《Solar physics》1986,106(1):29-33
Mt. Wilson numbers of spots data (as defined in Howard et al., 1984) appear to be distributed according to even-odd cycle numbering. Linear fits of annual numbers of spots versus annual sunspot number for even- and odd-numbered cycles have slopes which are statistically different at the 5% level of significance. The existence of an even-odd split in Mt. Wilson numbers of spots data may be due either to a real difference in even- and odd-numbered cycles on the Sun or to a difference in weather at Mt. Wilson (perhaps, related to the 22-yr rhythm of drought in the western United States) during even- and odd-numbered cycles, or both. For cycle 22, an even-numbered cycle, the peak numbers of spots is estimated to be near 2600. 相似文献
16.
Quasi-steady high-temperature current sheets are an energy source during the main or hot phase of solar flares. Such sheets are shown to be stabilized with respect to the tearing instability by a small transverse component of magnetic field existing in the sheets. 相似文献
17.
A study is made of Lyman continuum observations of solar flares, using data obtained by the Harvard College Observatory EUV spectroheliometer on the Apollo Telescope Mount. We find that there are two main types of flare regions: an overall mean flare coincident with the H flare region, and transient Lyman continuum kernels which can be identified with the H and X-ray kernels observed by other authors. It is found that the ground level hydrogen population in flares is closer to LTE than in the quiet Sun and active regions, and that the level of Lyman continuum formation is lowered in the atmosphere from a mass column density m 5/sx 10–6 g cm–2 in the quiet Sun to m 3/sx 10–4 g cm–2 in the mean flare, and to m 10–3g cm–2 in kernels. From these results we derive the amount of chromospheric material evaporated into the high temperature region, which is found to be - 1015g, in agreement with observations of X-ray emission measures. A comparison is made between kernel observations and the theoretical predictions made by model heating calculations, available in the literature; significant discrepancies are found between observation and current particle-heating models. 相似文献
18.
DOUBLE-LOOP CONFIGURATION OF SOLAR FLARES 总被引：2，自引：0，他引：2
We analyzed several flares, which are presumed to be caused by interactions between an emerging loop and an overlying loop. We call such a basic combination of loops a double-loop configuration, and we reveal its topology on the basis of the microwave and soft X-ray observations of the flares and the magnetograms. In many cases, the magnetic field of the flare loops shows a bipolar + remote unipolar structure, rather than a quadrapole structure. The footpoints of two loops are distributed in three magnetic patches, and two of the footpoints of the loops, one from the emerging loop and the other from the overlying loop, are included in a single magnetic polarity patch. Therefore, the two loops form a three-legged structure, and the two loops are not anti-parallel as assumed in the traditional reconnection models. Typically, the emergence of a parasitic polarity near the major preceding-polarity region or the following one in an active region creates this configuration, but, in one of the analyzed flares, two active regions are involved in the configuration. Not only the flares, but various other active phenomena – microflares, thermal plasma flows like jets, and surges – occur in the same magnetic configuration. Hence, the interaction between two loops, which forms the three-legged structure, is an important source of the various types of activity. 相似文献
19.
We present the results of an analysis of the east-west asymmetry in the solar flare distribution, observed during the years from 1976 to 1985. We conclude that flare events, all type of H flares, are not uniformly spread in heliolongitude over the solar disc when considering events with heliolongitudes greater than 60°, or even closer to central meridian for certain periods. This lack of homogeneity, however, does not have an influence on the definition of east-west asymmetries. Simple random distribution of flares over the solar disc can not account for the asymmetries found, but they can be explained in terms of the transit of active regions in front of the observer's position. Nonetheless, this is not the case for the distribution of flares equal or more intense than importance 1F observed during 1979. 相似文献
20.
A coronal bright point is resolved into a pattern of emission which, at any given time, consists of 2 or 3 miniature loops (each 2500 km in diameter and 12 000 km long). During the half-day lifetime of the bright point individual loops evolved on a time scale 6 min. A small ctive region seemed to evolve in this way, but the occasional blurring together of several loops made it difficult to follow individual changes. 相似文献