共查询到20条相似文献，搜索用时 46 毫秒
1.
In the following study our aim is to analyse the magnetic flux-rope topology of some events observed in the interplanetary medium related to ejecta. The magnetic field structures associated with interplanetary coronal mass ejections are globally classified in magnetic clouds and ejecta. One of the main questions regarding these phenomena concerns their flux-rope or non-flux-rope magnetic field line configuration. From the experimental measurements the only way to elucidate such a question is analysing the corresponding data by means of a flux-rope physical model. After selecting the ejecta events observed during the period 1997?–?2006, we have analysed them in light of an analytical model with that topology for the magnetic field components, initially developed for magnetic clouds, and with a non-force-free character; then, incorporating the expansion of the magnetic structure during their evolution in the interplanetary medium. Different parameters obtained from the fitting of the model are related to the orientation of the axis of the magnetic flux-rope structure and, additionally, the closest distance approach of the spacecraft to its axis. One of the main conclusions achieved concerns the fact that the axes of most of those structures are close to the Sun–Earth line, which implies that the passage of the spacecraft through the corresponding ejecta event is by its flank. In general, we show a rough procedure for the analysis and classification of ejecta in terms of their magnetic field topology. 相似文献
2.
The global 3-dimensional topology of the magnetic field of the weakly flaring active region AR 5420 in the early phase has been estimated using a series of photospheric longitudinal and vector magnetogams together with Hα filtergrams and white-light images. As a physical model for this task, we have used the assumption ofa force-free magnetic field character. An arcade-like structure of the magnetic field has been identified in the preflare phase with an apparent sheared configuration already present in the current-free field case. This system might have been an important source of generation of a field-aligned current system for the eruptions that followed. That was, in particular, suggeted by a significant extension of the active region area in the observation period from June 22 to 25, 1984, that resulted in a stronger shear of the detected arcade-like system. The atmospheric electric currents generated in such a way and the transition triggered by a large-amplitude perturbation generated by new flux emergences on June 23 at this place together might be the reason of the sequence of flares observed. Despite the changes in the Hα structure, the global force-free character of the field did not change significantly over the time of observations. The invariance (in the first order) of the force-free (nearly current-free) character of the magnetic field is consistent with the occurrence of relatively small flares only. 相似文献
3.
We show that the Hα luminosity and the Thomson optical depth of supernova iPTF14hls on day 600 after its discovery make it possible to estimate the envelope age at this stage, which turns out to be ~1000 days. A model that suggests the explosion of a massive star with a radius of ~2 × 1013 cm 450 days before the discovery is proposed. In the optimal model the ejecta mass is 30 M? with a kinetic energy of 8 × 1051 erg. The energy source at the main luminosity stage is presumably associated with the relativistic bipolar outflows produced by disk accretion onto a black hole. The [O I] 6300, 6364 Å doublet in the spectrum on day 600 is shown to be the result of emission from at least 1–3M? of oxygen in the central ejecta zone. The oxygen distribution is aspherical and can be represented both by two blue- and redshifted components (in the optically thin case) and by one blueshifted component in the case of optically thick lines at an oxygen filling factor of ~2 × 10?3. 相似文献
4.
An active region loop system was observed in a decaying active region for three hours by TRACE and BBSO in a joint campaign on September 27, 1998. Continuous mass motion was seen in Hα offband filtergrams throughout the three hours, and some UV loops were exhibited transient brightenings. We find that: (1) cool material was flowing along the loops at a speed of at least 20 km s?1. Further, in Hα red and blue wings, we see mass motion along different loops in opposite directions. This is the first report of a counter-streaming pattern of mass motion in an Hα loop system. (2) Transient brightenings of different UV loops at different times were observed at C?iv 1550 Å. These brightened UV loops were located in the same region and at the same altitudes as the Hα loops. The observations show a clear correlation between the transient brightenings of UV loops and mass motion in Hα loops. (3) Both footpoints of the loop system were located in regions of mixed magnetic polarities. Frequent micro-flares at one footpoint of the loops with small-scale brightenings spreading along the loop leg were observed before the brightening and rising of one C?iv loop. Similar to the case of a filament, the continuous mass motion along the loops seems important for maintaining the cool Hα loop system at coronal height. There may be an indication that the mass motion in cool Hα loops and the correlated transient brightening of the active region loops were due to the small-scale chromospheric magnetic reconnection at the footpoint regions of the loop system.
相似文献5.
In this paper we present simulations of an extragalactic jet interacting with a clumpy and filamentary narrow line region (NLR) similar to the one observed in NGC 1068. We study the kinematic disturbance produced by the interaction. Hα recombination emissivity maps and the spectral distribution of the emission are calculated. We find that ablation flows from high density clouds in the turbulent cocoon can produce fast, high emissivity flows, resulting in line widths of the order of 1000 km s-1 comparable to those observed in NGC 1068 and other Seyfert galaxies with radio ejecta. 相似文献
6.
We study the process of flux cancellation and filament formation in a nest of three decaying active regions, using data from SOHO MDI and EIT, and Hα images from Meudon and Big Bear. We find that there are no apparent EUV loops connecting the two poles of a cancelling feature prior to and during cancellation, suggesting an absence of coronal magnetic connectivity between these opposite polarity flux patches. We further find that the cancellation occurs at the ends of the Hα sections of the filament and is accompanied by a noticeable increase in Hα intensity and linkage of the Hα sections, but that the locations of the links remain the weakest in Hα absorption. We present our measurements of the amount of flux cancelled at each site and show it is in agreement with an estimate of the axial flux contained in the filament. We also observe two events of flux emergence, and find that they do not influence the filament formation in this case. We compare our results with similar measurements in recent papers and find agreement for the amounts of cancelled flux per patch, except for one case in a young emerging active region, for which we provide an alternative interpretation. We conclude that our measurements of flux cancellation are consistent with both the scenarios in which the filament is formed through ``head-to-tail" linkage, as well as the scenario in which filament flux tubes emerge as a whole from below the photosphere, but that only the former scenario is consistent with the apparent absence of coronal magnetic links between the cancelling magnetic patches. 相似文献
7.
Abstract— A simple granular flow model is used to investigate some of the conditions under which ejecta may flow as a granular media. The purpose of this investigation is to provide some bounds as to when either volatiles or an atmosphere are required to explain the fluid‐like morphology of many Martian ejecta deposits. We consider the ejecta deposition process from when an ejecta curtain first strikes a target surface via ballistics and possibly flows thereafter. A new finding is that either hard‐smooth surfaces or slightly erodible surfaces allow ejecta to flow readily as a granular medium. Neither volatiles nor an atmosphere are required to initiate flow. A low friction coefficient between ejecta grains can also generate flow and would be analogous to adding volatiles to the ejecta. The presence of either a rough or a densely packed erodible surface does not permit easy ejecta flow. High friction coefficients between ejecta grain also prevent flow, while changes in the coefficient of restitution (a measure of how much energy is retained after collisions between particles) plays a minor role in the flow dynamics of ejecta. A hard smooth or a somewhat erodible surface could be generated by past fluvial activity on Mars, which can either indurate a surface, erode and smooth a surface, or generate sedimentary terrains that are fairly easy to erode. No ramparts or layered ejecta morphologies are generated by our model, but this may be because several simplifying assumptions are used in our model and should not be construed as proof that either volatiles or an atmosphere are required to form fluidized ejecta morphologies. 相似文献
8.
We present a technique for automatic determination of flare ribbon separation and the energy released during the course of two-ribbon flares. We have used chromospheric Hα filtergrams and photospheric line-of-sight magnetograms to analyse flare ribbon separation and magnetic field structures, respectively. Flare ribbons were first enhanced and then extracted by the technique of “region growing”, i.e., a morphological operator to help resolve the flare ribbons. Separation of flare ribbons was then estimated from the magnetic-polarity reversal line using an automatic technique implemented into an Interactive Data Language (IDLTM) platform. Finally, the rate of flare-energy release was calculated using photospheric magnetic field data and the corresponding separation of the chromospheric Hα flare ribbons. This method could be applied to measure the motion of any feature of interest (e.g., intensity, magnetic, Doppler) from a given point of reference. 相似文献
9.
H observations, using the Multichannel Subtractive Double Pass (MSDP) spectrograph operating on the Meudon Solar Tower, have been made of an active region filament which undergoes a disparition brusque. The period of observation was from 10 45 to 13 30 UT on 22 June, 1981. Velocity and intensity fluctuations in H were measured. The proper motions of ejecta were followed allowing their trajectories and vector velocities to be determined. To model the dynamics of ejecta several models using thermal or magnetic driving forces are compared. The most promising model explains the motion as the consequence of magnetic stresses acting on an isolated magnetized plasmoïd in a diverging flux tube. 相似文献
10.
3D simulations of basin-scale lunar impacts are carried out to investigate: (a) the origins of strong crustal magnetic fields and unusual terrain observed to occur in regions antipodal to young large basins; and (b) the origin of enhanced magnetic and geochemical anomalies along the northwest periphery of the South Pole-Aitken (SPA) basin. The simulations demonstrate that a basin-forming impact produces a massive, hot, partially ionized cloud of vapor and melt that expands thermally around the Moon, converging near the basin antipode approximately 1 h after the impact for typical impact parameters. In agreement with previous work, analytic calculations of the interaction of this vapor-melt cloud with an initial ambient magnetic field predict a substantial temporary increase in field intensity in the antipodal region. The time of maximum field amplification coincides with a period when impacting ejecta also converge near the antipode. The latter produce antipodal shock stresses within the range of 5-25 GPa where stable shock remanent magnetization (SRM) of lunar soils has been found experimentally to occur. Calculated antipodal ejecta thicknesses are only marginally sufficient to explain the amplitudes of observed magnetic anomalies if mean magnetization intensities are comparable to those produced experimentally. This suggests that pre-existing ejecta materials, which would also contain abundant metallic iron remanence carriers, may be important anomaly sources, a possibility that is consistent with enhanced magnetic anomalies observed peripheral to SPA. The latter anomalies may be produced by amplified secondary ejecta impact shock waves in the thick SPA ejecta mantle occurring near the antipodes of the Imbrium and Serenitatis impacts. Together with converging seismic compressional waves, these antipodal impact shocks may have produced especially deep fracture zones along the northwest edge of SPA near the Imbrium antipode, allowing the ascent of magma with enhanced KREEP concentrations. 相似文献
11.
High‐resolution studies of double‐layered ejecta craters: Morphology,inherent structure,and a phenomenological formation model 
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下载免费PDF全文 The ejecta blankets of impact craters in volatile‐rich environments often possess characteristic layered ejecta morphologies. The so‐called double‐layered ejecta (DLE) craters are characterized by two ejecta layers with distinct morphologies. The analysis of high‐resolution image data, especially HiRISE and CTX, provides new insights into the formation of DLE craters. A new phenomenological excavation and ejecta emplacement model for DLE craters is proposed based on a detailed case study of the Martian crater Steinheim—a well‐preserved DLE crater—and studies of other DLE craters. The observations show that the outer ejecta layer is emplaced as medial and distal ejecta that propagate outwards in a debris avalanche or (if saturated with water) a debris flow mode after landing, overrunning previously formed secondary craters. In contrast, the inner ejecta layer is formed by a translational slide of the proximal ejecta deposits during the emplacement stage that overrun and superimpose parts of the outer ejecta layer. Based on our model, DLE craters on Mars are the result of an impact event into a rock/ice mixture that produces large amounts of shock‐induced vaporization and melting of ground ice, leading to high ejection angles, proximal landing positions, and an ejecta curtain with relatively wet (in terms of water in liquid form) composition in the distal part versus dryer composition in the proximal part. As a consequence, basal melting of ice components in the ejecta at the transient crater rim, which is induced by frictional heating and the enhanced pressure at depth, initiates an outwards directed collapse of crater rim material in a translational slide mode. Our results indicate that similar processes may also be applicable for other planetary bodies with volatile‐rich environments, such as Ganymede, Europa, and the Earth. 相似文献
12.
A model was developed for the mass distribution of fragments that are ejected at a given velocity for impact and explosion craters. The model is semiempirical in nature and is derived from (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationships between maximum ejecta fragment size and crater diameter, (4) measurements of maximum ejecta size versus ejecta velocity, and (5) an assumption on the functional form for the distribution of fragments ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity is broad; e.g., 68% of the mass of the ejecta at a given velocity contains fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. Using this model, we have calculated the largest fragment that can be ejected from asteroids, the Moon, Mars, and Earth as a function of crater diameter. The model is unfortunately dependent on the size-dependent ejection velocity limit for which only limited data are presently available from photography of high explosive-induced rock ejecta. Upon formation of a 50-km-diameter crater on an atmosphereless planet having the planetary gravity and radius of the Moon, Mars, and Earth, fragments having a maximum mean diameter of ≈30, 22, and 17 m could be launched to escape velocity in the ejecta cloud. In addition, we have calculated the internal energy of ejecta versus ejecta velocity. The internal energy of fragments having velocities exceeding the escape velocity of the moon (～2.4 km/sec) will exceed the energy required for incipient melting for solid silicates and thus, the fragments ejected from Mars and the Earth would be melted. 相似文献
13.
A large filament was observed during a multi-wavelength coordinated campaign on June 19, 1998 in the Hα line with the Swedish Vacuum Solar Telescope (SVST) at La Palma, in the coronal lines Fe ix/x 171 Å and Fe xi 195 Å with the Transition Region and Coronal Explorer (TRACE) and in EUV lines with the SOHO/CDS spectrometer and the hydrogen Lyman series with the SOHO/SUMER spectrometer. Because of its high-latitude location, it is possible to disentangle the physical properties of the Hα filament and the filament channel seen in EUV lines. TRACE images point out a dark region fitting the Hα fine-structure threads and a dark corridor (filament channel), well extended south of the magnetic inversion line. A similar pattern is observed in the CDS EUV-line images. The opacity of the hydrogen and helium resonance continua at 171 Å is almost two orders of magnitude lower than that at the Hi head (912 Å) and thus similar to the opacity of the Hα line. Since we do not see the filament channel in Hα, this would imply that it should also be invisible in TRACE lines. Thus, the diffuse dark corridor is interpreted as due to the coronal ‘volume blocking’ by a cool plasma which extends to large altitudes. Such extensions were also confirmed by computing the heights from the projection geometry and by simulations of the CDS and TRACE line intensities using the spectroscopic model of EUV filaments (Heinzel, Anzer, and Schmieder, 2003). Finally, our NLTE analysis of selected hydrogen Lyman lines observed by SUMER also leads to a conclusion that the dark filament channel is due to a presence of relatively cool plasma having low densities and being distributed at altitudes reaching the Hα filament. 相似文献
14.
Observations using a narrow band Hα filter still remain one of the best ways to investigate the fine structures and internal dynamics of solar filaments. Hα observations, however, have been usually carried out with the peak response of the filter fixed at a single wavelength, usually at the centerline, in which the investigation is limited to the Hα morphology and its time evolution. In this paper, we demonstrate that the Hα spectroscopy that takes Hα images successively at several wavelengths is a useful tool in the study of solar filaments on the solar disk. Our observation of a filament was carried out on August 3, 2004 at Big Bear Solar Observatory using the 10-inch refractor. The Lyot Hα filter was successively tuned to five wavelengths: ?0.6, ?0.3, 0.0, +0.3, and +0.6 Å from the Hα line center. Each set of wavelength scan took 15 s. After several steps of data reduction, we have constructed a five-wavelength spectral profile of intensity contrast at every spatial point. The contrast profile at each spatial point inside the filament was reasonably well fit by the cloud model as far as the contrast is high enough, and allowed us to construct the maps of τ0, v, Δ λD and S in the filament. We also found that the line center method that is often used, always yields line-of-sight velocities that are systematically lower than the cloud model fit. Our result suggests that taking Hα images at several wavelengths using a tunable filter provides an effective way of deriving physically meaningful parameters of solar filaments. Particularly constructing the time sequence of v maps appears to be a useful tool for the study of internal dynamics, like counterstreaming, in filaments. 相似文献
15.
Charles Joseph Byrne 《Earth, Moon, and Planets》2007,101(3-4):153-188
The differences between the surface structure of the near side and the far side of the Moon have been topics of interest ever
since photographs of the far side have been available. One recurrent hypothesis is that a large impact on the near side has
deposited ejecta on the far side, resulting in thicker crust there. Specific proposals were made by P.H. Cadogan for the Gargantuan
Basin and by E.A. Whitaker for the Procellarum Basin. Despite considerable effort, no consensus has been reached on the existence
of these basins. The problem of searching for such a basin is one of finding its signature in a somewhat chaotic field of
basin and crater impacts. The search requires a model of the topographic shape of an impact basin and its ejecta field. Such
a model is described, based on elevation data of lunar basins collected by the Lidar instrument of the Clementine mission
and crustal thickness data derived from tracking Clementine and other spacecraft. The parameters of the model are scaled according
to the principles of dimensional analysis and isostatic compensation in the early Moon. The orbital dynamics of the ejecta
and the curvature of the Moon are also taken into account. Using such a scaled model, a search for the best fit for a large
basin led to identification of a basin whose cavity covers more than half the Moon, including the area of all of the impact
basins visible on the near side. The center of this basin is at 22 degrees east longitude and 8.5 degrees north latitude and
its average radius is approximately 3,160 km. It is a megabasin, a basin that contains other basins (the far side South Pole-Aitken
Basin also qualifies for that designation). It has been called the Near Side Megabasin. Much of the material ejected from
the basin escaped the Moon, but the remainder formed an ejecta blanket that covered all of the far side beyond the basin rim
to a depth of from 6 to 30 km. Isostatic compensation reduced the depth relative to the mean surface to a range of 1–5 km,
but the crustal thickness data reveals the full extent of the original ejecta. The elevation profile of the ejecta deposited
on the far side, together with modification for subsequent impacts by known basins (especially the far side South Pole-Aitken
Basin) matches the available topographic data to a high degree. The standard deviation of the residual elevations (after subtracting
the model from the measured elevations) is about one-half of the standard deviation of the measured elevations. A section
on implications discusses the relations of this giant basin to known variations in the composition, mineralogy, and elevations
of different lunar terranes. 相似文献
16.
Daniel D. DURDA Clark R. CHAPMAN William J. MERLINE Brian L. ENKE 《Meteoritics & planetary science》2012,47(6):1087-1097
Abstract– We present results of a numerical model of the dynamics of ejecta emplacement on asteroid 433 Eros. Ejecta blocks represent the coarsest fraction of Eros’ regolith and are important, readily visible, “tracer particles” for crater ejecta‐blanket units that may be linked back to specific source craters. Model results show that the combination of irregular shape and rapid rotation of an asteroid can result in markedly asymmetric ejecta blankets (and, it follows, ejecta block spatial distribution), with locally very sharp/distinct boundaries. We mapped boulder number densities in NEAR‐Shoemaker MSI images across a portion of a predicted sharp ejecta‐blanket boundary associated with the crater Valentine and confirm a distinct and real ejecta‐blanket boundary, significant at least at the 3‐sigma level. Using our dynamical model, we “back track” the landing trajectories of three ejecta blocks with associated landing tracks in an effort to constrain potential source regions where those blocks were ejected from Eros’ surface in impact events. The observed skip distances of the blocks upon landing on Eros’ surface and the landing speeds and elevation angles derived from our model allow us to estimate the coefficient of restitution, ε, of Eros’ surface for impacts of 10‐m‐scale blocks at approximately 5 m s?1 impact speeds. We find mean values of ε of approximately 0.09–0.18. 相似文献
17.
On 11 January 2002, using the Multi-channel Infrared Solar Spectrograph (MISS) at the Purple Mountain Observatory (PMO), we obtained Hα, Ca ii 8542 Å and He i 10?830 Å spectra and slit-jaw Hα images of a peculiar solar limb event. A close resemblance of its intensity to that of a small flare and the GOES X-ray flux indicates that it was an active prominence. However, its morphological evolution and velocity variation were different from general typical active prominences, such as limb flares, post-flare loops, surges and sprays. It started with the ejection of material from the flare site. In the early phase, the ejecta was as bright as a limb flare and kept rising until reaching the height of (8????10)×104 km at an almost constant velocity of 91.7 km? s ?1 with its lower part always connected to the solar surface. EUV images in 195 Å show similar structure as in the Hα line, indicating the coexistence of plasmas with temperatures differing by more than two orders of magnitude. Later some material started to fall back to another bright area on the solar surface. The falling material did not show the collimated structure of surges or the arc structure of flaring arches. A red-shift velocity of more than 200 km? s ?1 was detected in a bright point close to the outer edge of the closed loop system formed later, which dispersed in a few minutes and became a part of the newly formed large loop. The ejected material did not leave the sun, indicating that the magnetic reconnection was not sufficient to remove the overlying field lines during the process. The spectral line profiles showed large widths and variable velocities, and therefore the line-pair method is not applicable to this event for the estimation of physical parameters. 相似文献
18.
A Monte Carlo code ( artis ) for modelling time-dependent three-dimensional spectral synthesis in chemically inhomogeneous models of Type Ia supernova ejecta is presented. Following the propagation of γ-ray photons, emitted by the radioactive decay of the nucleosynthesis products, energy is deposited in the supernova ejecta and the radiative transfer problem is solved self-consistently, enforcing the constraint of energy conservation in the comoving frame. Assuming a photoionization-dominated plasma, the equations of ionization equilibrium are solved together with the thermal balance equation adopting an approximate treatment of excitation. Since we implement a fully general treatment of line formation, there are no free parameters to adjust. Thus, a direct comparison between synthetic spectra and light curves, calculated from hydrodynamic explosion models, and observations is feasible. The code is applied to the well-known W7 explosion model and the results tested against other studies. Finally, the effect of asymmetric ejecta on broad-band light curves and spectra is illustrated using an elliptical toy model. 相似文献
19.
D. G. KORYCANSKY Catherine S. PLESKO Martin JUTZI Erik ASPHAUG Anthony COLAPRETE 《Meteoritics & planetary science》2009,44(4):603-620
Abstract— We describe the results of a variety of model calculations for predictions of observable results of the LCROSS mission to be launched in 2009. Several models covering different aspects of the event are described along with their results. Our aim is to bracket the range of expected results and produce a useful guide for mission planning. In this paper, we focus on several different questions, which are modeled by different methods. The questions include the size of impact crater, the mass, velocity, and visibility of impact ejecta, and the mass and temperature of the initial vapor plume. The mass and velocity profiles of the ejecta are of primary interest, as the ejecta will be the main target of the S‐S/C observations. In particular, we focus on such quantities as the amount of mass that reaches various heights. A height of 2 km above the target is of special interest, as we expect that the EDUS impact will take place on the floor of a moderate‐sized crater ?30 km in diameter, with a rim height of 1–2 km. The impact ejecta must rise above the crater rim at the target site in order to scatter sunlight and become visible to the detectors aboard the S‐S/C. We start with a brief discussion of crater scaling relationships as applied to the impact of the EDUS second stage and resulting estimated crater diameter and ejecta mass. Next we describe results from the RAGE hydrocode as applied to modeling the short time scale (t 0.1 s) thermal plume that is expected to occur immediately after the impact. We present results from several large‐scale smooth‐particle hydrodynamics (SPH) calculations, along with results from a ZEUS‐MP hydrocode model of the crater formation and ejecta mass‐velocity distribution. We finish with two semi‐analytic models, the first being a Monte Carlo model of the distribution of expected ejecta, based on scaling models using a plausible range of crater and ejecta parameters, and the second being a simple model of observational predictions for the shepherding spacecraft (S‐S/C) that will follow the impact for several minutes until its own impact into the lunar surface. For the initial thermal plume, we predict an initial expansion velocity of ?7 km s?1, and a maximum temperature of ?1200 K. Scaling relations for crater formation and the SPH calculation predict a crater with a diameter of ?15 m, a total ejecta mass of ?106kg, with ?104kg reaching an altitude of 2 km above the target. Both the SPH and ZEUS‐MP calculations predict a maximum ejecta velocity of ?1 km s?1. The semi‐analytic Monte Carlo calculations produce more conservative estimates (by a factor of ?5) for ejecta at 2 km, but with a large dispersion in possible results. 相似文献
20.
Using TRACE EUV 171 Å line, Hα line, Zürich radio, RHESSI, and HXRS observations the 29 September 2002 flare (M2.6), which occurred in AR NOAA 0134, was analyzed. Flaring structures were compared with a potential magnetic field model (field lines and quasi-separatrix layers) made from SOHO/MDI full-disk magnetogram. Series of high-resolution SOHO/MDI magnetograms and TRACE white-light images were used to find changes in the active region at the photosphere during the flare. The flare began with a rising of a small dark loop followed by the flare brightening observed in 171 Å with TRACE and Hα lines. In radio wavelengths, first type III bursts were observed 5 min prior to the start of hard X-ray emission, indicating a pre-flare coronal activity. The main hard X-ray emission peak (at 06:36 UT) was associated with the second type III burst activity and several slowly negatively drifting features, all starting from one point on the radio spectrum (probably a shock propagating through structures with different plasma parameters). After this time a huge loop formed and three minutes later it became visible in absorption both in Hα and 171 Å EUV lines. The phase of huge dark loop formation was characterized by long-lasting, slowly negatively drifting pulsations and drifting continuum. Finally, considering this huge loop as a surge an evolution of the event under study is discussed. 相似文献