排序方式： 共有19条查询结果，搜索用时 125 毫秒
1.
On 11 September 1973 a peculiar prominence was observed. The prominence displayed strong ( 50km s–1) systematic motions toward and away from the observer. The unusual spectrographic appearance of the prominence might have been due to downflowing material lifted into the corona during an earlier coronal transient.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
2.
The origin of the material which is ejected during a white light coronal transient has not been determined heretofore. Study of a disturbance on 26 and 27 August 1973, during which a slowly ascending prominence and a more rapid accompanying coronal transient were simultaneously observed, helps to resolve this question. Prominence images obtained in Hα 6563 Å and in He II 304 Å are nearly identical. The mass ejection transient observed in white light (3700–7000 Å) appeared to be a loop about 1 R⊙ higher than the top of the ascending prominence; it accelerated away from the prominence below it. These observations imply: (1) the bulk of the ejected material did not originate in the ascending prominence; (2) therefore, most of the material must have come from the low corona above the prominence, (and was at coronal temperatures during its outward passage); and (3) the total event - ascending prominence accompanied by coronal mass ejection - was far larger, more energetic, and longer lasting than would be inferred from the prominence observations alone. The transient of 26–27 August was slow and of atypical shape compared to other mass ejection transients, but we believe that these three conclusions apply to most, if not all, of the more than 60 loop-shaped coronal transients observed by the High Altitude Observatory's coronagraph during the nine-month flight of Skylab. 相似文献
3.
V. J. Pizzo S. M. Hill C. C. Balch D. A. Biesecker P. Bornmann E. Hildner R. N. Grubb E. G. Chipman J. M. Davis K. S. Wallace K. Russell S. A. Cauffman T. T. Saha G. D. Berthiume 《Solar physics》2005,226(2):283-315
The Solar X-ray Imager (SXI) was launched on 23 July 2001 on NOAAs GOES-12 satellite and completed post-launch testing on 20 December 2001. It was brought into operations on 21 January 2003. This paper documents SXI performance and calibrations prior to an instrument degradation that occurred on 5 November 2003 and thus covers more than 420000 soft X-ray images of the Sun. This paper details component-level as well as full-system calibrations characterizing the spatial and spectral performance of the instrument, including the grazing-incidence mirror, filters, and the properties of the MCP-intensified CCD detector system. Routine image corrections are also described. These include background (dark current) subtraction, flat-fielding, off-band light-leak correction, and image pointing and timing considerations. In addition, a signal-to-noise analysis is presented. The information contained in this study is intended to enable researchers to conduct quantitative analysis of GOES-12 SXI images. 相似文献
4.
J. T. Gosling E. Hildner R. M. Macqueen R. H. Munro A. I. Poland C. L. Ross 《Solar physics》1975,40(2):439-448
Numerous mass ejections from the Sun have been detected with orbiting coronagraphs. Here for the first time we document and discuss the direct association of a coronagraph observed mass ejection, which followed a 2B flare, with a large interplanetary shock wave disturbance observed at 1 AU. Estimates of the mass (2.4 × 1016 g) and energy content (1.1 × 1032 erg) of the coronal disturbance are in reasonably good agreement with estimates of the mass and energy content of the solar wind disturbance at 1 AU. The energy estimates as well as the transit time of the disturbance are also in good agreement with numerical models of shock wave propagation in the solar wind. 相似文献
5.
An eruptive prominence and coronal transient of 19 December, 1973 comprised one of the best-observed coronal mass ejection events during the skylab period (May, 1973–January, 1974). EUV observations show that the pre-eruptive quiescent prominence was (at 8000 K) not appreciably hotter than other quiescent prominences, but EUV radiation from it and its prominence-corona interface was unusually faint. The prominence material was distributed in helical threads which decreased in pitch angle during the early phases of eruption. No region of the prominence was markedly different from any other just prior to and during the eruption. For the first time, the temperature and density of rising prominence material were determined at great heights in the corona. At 3R
, the prominence material was still confined in threads whose temperature and total hydrogen density were 2 × 104 K and 1.5 × 109 cm–3, respectively. Shortly after this observation ( 7hr after the start of the eruption), the prominence material expanded dramatically. A small portion (1%) of the prominence material was observed draining downward near the solar surface late in the event, and we infer that only a small fraction (10%) of the pre-eruptive prominence mass was expelled from the Sun. The remainder of the prominence apparently lay outside the instruments' fields of view. The bulk of the material expelled did not originate in the prominence. Both coronal and prominence material accelerated outward during the period of observations. A pre-existing streamer was disrupted by the outflowing material.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
6.
The large loop or blob-like transient events viewed in the white-light corona are rimmed by broad regions where the density is slightly enhanced above the pre-transient corona. Every one of the Skylab events studied for which sufficiently good Skylab coronagraph coverage is available shows this effect. The upper boundaries of these forerunners blend gradually into the background corona 1 to 2R
above the transients' leading edges. In any single event, the coronal mass enhancement represented by the forerunner comprises up to 25% of the total excess mass present in the coronagraph's field of view and includes a much larger volume of the corona than previously attributed to the underlying transient. We have not yet seen a forerunner without an accompanying transient. Clearly, forerunners must be reckoned with in any proposed models of discrete outward coronal mass motions, because they indicate the presence of disturbed corona far ahead of the denser portions of the event.Skylab Solar Workshop Postdoctoral Appointee 1975–78. The Skylab Solar Workshops are sponsored by NASA and NSF and managed by the High Altitude Observatory.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
7.
An asymmetric, expanding arch, photographed in the inner corona with an X-ray telescope on 13 August, 1973, is identified as the source of the mass ejected in a white light transient in the outer corona. The morphology, angular position, estimated mass and apparent rate of upward acceleration of the lower coronal arch are similar to those of the arch seen passing through the outer corona. The mass of material removed from the lower corona is estimated at 2 × 1015 g, and the upward movement is consistent with a constant acceleration of 12.5 m s–2 between 1.3 and 5 R.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
8.
We model the formation of solar quiescent prominences by solving numerically the non-linear, time-dependent, magnetohydrodynamic equations governing the condensation of the corona. A two-dimensional geometry is used. Gravitational and magnetic fields are included, but thermal conduction is neglected. The coronal fluid is assumed to cool by radiation and to be heated by the dissipation of mechanical energy carried by shock waves. A small, isobaric perturbation of the initial thermal and mechanical equilibrium is introduced and the fluid is allowed to relax. Because the corona with the given energy sources is thermally unstable, cooling and condensation result.When magnetic and gravitational fields are absent, condensation occurs isotropically with a strongly time-dependent growth rate, and achieves a density 18 times the initial density in 3.5 × 104 s. The rapidity of condensation is limited by hydrodynamical considerations, in contrast to the treatment of Raju (1968). When both magnetic and gravitational fields are included, the rate of condensation is inhibited and denser material falls.We conclude that: (1) condensation of coronal material due to thermal instability is possible if thermal conduction is inhibited; (2) hydrodynamical processes determine, in large part, the rate of condensation; (3) condensation can occur on a time scale compatible with the observed times of formation of quiescent prominences.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
9.
R. M. MacQueen A. Csoeke-Poeckh E. Hildner L. House R. Reynolds A. Stanger H. Tepoel W. Wagner 《Solar physics》1980,65(1):91-107
The High Altitude Observatory Coronagraph/Polarimeter, to be flown on the National Aeronautics and Space Administration's Solar Maximum Mission satellite, is designed to produce images of the solar corona in seven wavelength bands in the visible spectral range. The spectral bands have been chosen to specifically exclude or include chromospheric spectral lines, so as to allow discrimination between ejecta at high (coronal) and low (chromospheric) temperatures, respectively. In addition, the instrument features spectral filters designed to permit an accurate color separation of the F and K coronal components, and a narrow band (5.5 Å) filter to observe the radiance and polarization of the Fe xiv 5303 Å line. The effective system resolution is better than 10 arc sec and the instrument images a selected quadrant (or smaller field) on an SEC vidicon detector. The total height range that may be recorded encompasses 1.6 to more than 6.0R
(from Sun center). The instrument is pointed independently of the SMM spacecraft, and its functions are controlled through the use of a program resident within the onboard spacecraft computer. Major experimental goals include: (a) Observation of the role of the corona in the flare process and of the ejecta from the flare site and the overlying corona; (b) the study of the direction of magnetic fields in stable coronal forms, and, perhaps, ejecta; and (c) examination of the evolution of the solar corona near the period of solar maximum activity.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
10.
Elliot Hildner Andreas Klügel Folkmar Hauff 《Contributions to Mineralogy and Petrology》2011,162(4):751-772
The 1995 eruption of Fogo (Cape Verde Islands) differed from previous eruptions by the occurrence of evolved lavas, the SW-orientation
of vents, and pre-eruptive seismicity between Fogo and the adjacent (~20 km) island of Brava. We have conducted a thermobarometric
and chemical study of this eruption in order to reconstruct its magma plumbing system and to test for possible connections
to Brava. The bimodal eruption produced basanites (5.2–6.7 wt% MgO) and phonotephrites (2.4–2.8 wt% MgO) that are related
by fractional crystallization. Clinopyroxene-melt-barometry of phenocrysts yields pressure ranges of 460–680 MPa for the basanites
and 460–520 MPa for the phonotephrites. Microthermometry of CO2-dominated fluid inclusions in olivine and clinopyroxene phenocrysts yields systematically lower pressure ranges of 200–310 MPa
for basanites and 270–470 MPa for phonotephrites. The combined data indicate pre-eruptive storage of the 1995 magmas within
the lithospheric mantle between 16 and 24 km depth. During eruption, the ascending magmas stalled temporarily at 8–11 km depth,
within the lower crust, before they ascended to the surface in a few hours as indicated by zonations of olivine phenocrysts.
Our data provide no evidence for magma storage at shallow levels (<200 MPa) or lateral magma movements beneath the Fogo-Brava
platform. Sr–Nd–Pb isotope ratios of samples from Brava differ significantly from those of the 1995 and older Fogo lavas,
which rules out contamination of the 1995 magmas by Brava material and indicates different mantle sources and magma plumbing
systems for both islands. 相似文献