Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer   总被引：1，自引：0，他引：1  

J. C. Raymond  J. L. Kohl  G. Noci  E. Antonucci  G. Tondello  M. C. E. Huber  L. D. Gardner  P. Nicolosi  S. Fineschi  M. Romoli  D. Spadaro  O. H. W. Siegmund  C. Benna  A. Ciaravella  S. Cranmer  S. Giordano  M. Karovska  R. Martin  J. Michels  A. Modigliani  G. Naletto  A. Panasyuk  C. Pernechele  G. Poletto  Peter L. Smith  R. M. Suleiman  L. Strachan 《Solar physics》1997,175(2):645-665

The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers the 940–1350 Å range as well as the 470–630 Å range in second order. It has detected coronal emission lines of H, N, O, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance scattering of emission lines from the solar disk dominates the intensities of a few lines, but electron collisional excitation produces most of the lines observed. Resonance, intercombination and forbidden lines are seen, and their relative line intensities are diagnostics for the ionization state and elemental abundances of the coronal gas. The elemental composition of the solar corona and solar wind vary, with the abundance of each element related to the ionization potential of its neutral atom (First Ionization Potential–FIP). It is often difficult to obtain absolute abundances, rather than abundances relative to O or Si. In this paper, we study the ionization state of the gas in two coronal streamers, and we determine the absolute abundances of oxygen and other elements in the streamers. The ionization state is close to that of a log T = 6.2 plasma. The abundances vary among, and even within, streamers. The helium abundance is lower than photospheric, and the FIP effect is present. In the core of a quiescent equatorial streamer, oxygen and other high-FIP elements are depleted by an order of magnitude compared with photospheric abundances, while they are depleted by only a factor of 3 along the edges of the streamer. The abundances along the edges of the streamer (‘legs’) resemble elemental abundances measured in the slow solar wind, supporting the identification of streamers as the source of that wind component.  相似文献   

Imaging and mechanical property measurements of kerogen via nanoindentation     

Jonathan C. Zeszotarski  Richard P. Vinci  Raymond Michels 《Geochimica et cosmochimica acta》2004,68(20):4113-4119

Most analyses of kerogens rely on samples that have been isolated by dissolving the rock matrix. The properties of the kerogen before and after such isolation may be different and all sample orientation information is lost. We report a method of measuring kerogen mechanical properties in the rock matrix without isolation. An atomic force microscope (AFM) based nanoindenter is used to measure the hardness and reduced modulus of the kerogen within Woodford shale. The same instrument also provides useful images of polished rock sections on a submicrometer scale. Measurements were carried out both parallel and perpendicular to the bedding plane.  相似文献   

Depositional regimes in the Norwegian-Greenland Sea: the last two glacial to interglacial transitions     

R. Henrich  T. Wagner  P. Goldschmidt  K. Michels 《International Journal of Earth Sciences》1995,84(1):28-48

Various models of surface and deep-water circulation in the Norwegian-Greenland Sea (NGS) have been proposed for the last two glacial to interglacial transitions. Although much progress has been made in understanding the sedimentary response to climatic and oceanographic changes, conflicting interpretations have been developed. To clarify some of these discrepancies and to test or modify the existing circulation concepts, a multiparameter approach is applied, combining sedimentological, micropaleontological, organic-geochemical and isotopic methods. On the basis of indicative properties a combined litho- and organofacies concept is developed and calibrated with modern depositional settings beneath different surface water masses. Sedimentary regimes are then derived for glacial and deglacial settings.Atlantic water intrusions in the NGS reveal complex and highly dynamic patterns for the last two glacial and interglacial periods, with repetitive inflows during Isotope Stage 6 and a high variability in Isotope Stage 5. Specific facies patterns show maximum extensions of Atlantic Water intrusions during the climatic highstands 5.5.1, 5.3 and 5.1 and narrowest intrusions in the cool phases 5.4 and most pronounced in 5.2. In contrast, different glacio-marine depositional regimes depict variable sea ice coverage and supply of ice-rafted debris. Most conspicuous are short-term depositional events marked by diamictons, which are related to the high instabilities of continental ice sheets. Some of the diamictons seem to occur contemporaneously with Heinrich layers H1 and H2. The probable temporal and obvious phenomenological concidence of Heinrich layers and NGS diamictons suggests a common trigger mechanism which caused an almost simultaneous disintegration of huge continental ice masses along the shelves of North America and the eastern margin of the NGS.A previous estuarine circulation model claims regional upwelling along the eastern margin of the NGS for specific periods of the last deglaciation. The organic character of sediments covering the same time intervals show a clear predominance of reworked fossil organic matter and thus does not support the estuarine model.  相似文献   

Eit and LASCO Observations of the Initiation of a Coronal Mass Ejection   总被引：2，自引：0，他引：2  

K. P. Dere  G. E. Brueckner  R. A. Howard  M. J. Koomen  C. M. Korendyke  R. W. Kreplin  D. J. Michels  J. D. Moses  N. E. Moulton  D. G. Socker  O. C. St. Cyr  J. P. Delaboudinière  G. E. Artzner  J. Brunaud  A. H. Gabriel  J. F. Hochedez  F. Millier  X. Y. Song  J. P. Chauvineau  J. P. Marioge  J. M. Defise  C. Jamar  P. Rochus  R. C. Catura  J. R. Lemen  J. B. Gurman  W. Neupert  F. Clette  P. Cugnon  E. L. Van Dessel  P. L. Lamy  A. Llebaria  R. Schwenn  G. M. Simnett 《Solar physics》1997,175(2):601-612

We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 100 km s^-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200–400 km s^-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 10⁴ km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb.  相似文献   

Recognition of contour-current influence in mixed contourite-turbidite sequences of the western Weddell Sea,Antarctica     

Michels  Klaus H.  Rogenhagen  Johannes  Kuhn  Gerhard 《Marine Geophysical Researches》2001,22(5-6):465-485

Sedimentary processes and structures across the continental rise in the western Weddell Sea have been investigated using sediment acoustic and multichannel seismic data, integrated with multibeam depth sounding and core investigations. The results show that a network of channels with associated along-channel ridges covers the upper continental slope. The seismic profiles reveal that the channels initially developed as erosive turbidite channels with associated levees on their northern side due to Coriolis force. Later they were partly or fully infilled, probably as a result of decreasing turbidite activity. Now the larger ones exist as erosive turbidite channels of reduced size, whereas the smaller ones are non-erosive channels, their shape being maintained by contour current activity. Drift bodies only developed where slumps caused a distinctive break in slope inclination on the upper continental rise, which served to initiate the growth of a drift body fed by contour currents or by the combined action of turbidites and contourites. The history of sedimentation can be reconstructed tentatively by correlation of seismo-stratigraphic units with the stages of evolution of the drifts on the western side of the Antarctic Peninsula. Three stages can be distinguished in the western Weddell Sea after a pre-drift stage, which is delimited by an erosional unconformity at the top: (1) a growth stage, dominated by turbidites, with occasional occurrence of slumps during its initial phase; (2) during a maintenance stage turbiditiy-current intensity (and presumably sedimentation rate also) decreased, probably as a result of the ice masses retreating from the shelf edge, and sedimentation became increasingly dominated by contour current activity; and (3) a phase of sheeted-sequence formation. A southward decrease in sediment thickness shows that the Larsen Ice Shelf plays an important role in sediment delivery to the western Weddell Sea. This study shows that the western Weddell Sea has some characteristics in common with the southern as well as the northwestern Weddell Sea: contour currents off the Larsen Ice Shelf have been present for a long time, probably since the late Miocene, but during times of high sediment input from the shelves as a result of advancing ice masses a channel-levee system developed and dominated over the contour-current transport of sediment. At times of relatively low sediment input the contour-current transport dominated, leading to the formation of drift deposits on the upper continental rise. Seaward of areas without shelf ice masses the continental rise mainly shows a rough topography with small channels and underdeveloped levees. The results demonstrate that sediment supply is an important, maybe the controlling factor of drift development on the Antarctic continental rise.  相似文献   

Characteristics of flares producing metric type II bursts and coronal mass ejections     

S. Kahler  N. R. Sheeley Jr.  R. A. Howard  M. J. Koomen  D. J. Michels 《Solar physics》1984,93(1):133-141

We attempt to study the origin of coronal shocks by comparing several flare characteristics for two groups of flares: those with associated metric type II bursts and coronal mass ejections (CMEs) and those with associated metric type II bursts but no CMEs. CMEs accompany about 60% of all flares with type II bursts for solar longitudes greater than 30°, where CMEs are well observed with the NRL Solwind coronagraph. H flare areas, 1–8 Å X-ray fluxes, and impulsive 3 cm fluxes are all statistically smaller for events with no CMEs than for events with CMEs. It appears that both compact and large mass ejection flares are associated with type II bursts. The events with no CMEs imply that at least many type II shocks are not piston-driven, but the large number of events of both groups with small 3 cm bursts does not support the usual assumption that type II shocks are produced by large energy releases in flare impulsive phases. The poor correlation between 3 cm burst fluxes and the occurrence of type II bursts may be due to large variations in the coronal Alfvén velocity.Sachs/Freeman Associates, Inc., Bowie, MD 20715, U.S.A.  相似文献   

Fossil Fuel Saving through a Direct Solar Energy Water Heating System     

Ademar Michels  Flávio Dias Mayer  Roger Gallon  Ronaldo Hoffmann  Seimur Tiago Serafini 《洁净——土壤、空气、水》2008,36(9):743-747

The global warming and energy crisis is motivating the search for sustainable power sources. The objective of this work is to analyze the economic return and quantify the reduction in the emission of pollutants, when low‐cost solar collectors are used as a partial substitute for a boiler that uses fuel oil as the energy source, in order to heat water for the swimming pools of the Physical Education Center, Federal University of Santa Maria. The collectors are made from PVC and other easily acquired materials. The estimations for energy saving are based on a collecting area of 182 m². From knowledge of the collectors' efficiency, the mathematical demonstration shows a fuel oil saving of 13,174 kg, representing 24% of the total amount consumed per annum. The investment required for the construction and installation of the collectors is US$ 6,445 and the estimated useful live is five years. The internal rate of return is 30%. The emission of pollutants is reduced by a considerable amount of 41,213 kg CO₂ equivalent/year. The use of direct sun energy as an alternative power source represents a significant economic interest as well as contributing to the mitigation of greenhouse gases.  相似文献   

First View of the Extended Green-Line Emission Corona At Solar Activity Minimum Using the Lasco-C1 Coronagraph on Soho     

R. Schwenn  B. Inhester  S. P. Plunkett  A. Epple  B. Podlipnik  D. K. Bedford  C. J. Eyles  G. M. Simnett  S. J. Tappin  M. V. Bout  P. L. Lamy  A. Llebaria  G. E. Brueckner  K. P. Dere  R. A. Howard  M. J. Koomen  C. M. Korendyke  D. J. Michels  J. D. Moses  N. E. Moulton  S. E. Paswaters  D. G. Socker  O. C. St. Cyr  D. Wang 《Solar physics》1997,175(2):667-684

The newly developed C1 coronagraph as part of the Large-Angle Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft has been operating since January 29, 1996. We present observations obtained in the first three months of operation. The green-line emission corona can be made visible throughout the instrument's full field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured from Sun center). Quantitative evaluations based on calibrations cannot yet be performed, but some basic signatures show up even now: (1) There are often bright and apparently closed loop systems centered at latitudes of 30° to 45° in both hemispheres. Their helmet-like extensions are bent towards the equatorial plane. Farther out, they merge into one large equatorial ‘streamer sheet’ clearly discernible out to 32 R⊙. (2) At mid latitudes a more diffuse pattern is usually visible, well separated from the high-latitude loops and with very pronounced variability. (3) All high-latitude structures remain stable on time scales of several days, and no signature of transient disruption of high-latitude streamers was observed in these early data. (4) Within the first 4 months of observation, only one single ‘fast’ feature was observed moving outward at a speed of 70 km s^-1 close to the equator. Faster events may have escaped attention because of data gaps. (5) The centers of high-latitude loops are usually found at the positions of magnetic neutral lines in photospheric magnetograms. The large-scale streamer structure follows the magnetic pattern fairly precisely. Based on our observations we conclude that the shape and stability of the heliospheric current sheet at solar activity minimum are probably due to high-latitude streamers rather than to the near-equatorial activity belt. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004948913883  相似文献   

Äber Trockenrisse,Regentropfen und ähnliche Bildung unter Wasser     

F. Michels 《International Journal of Earth Sciences》1933,24(3-4):272-272

Ohne Zusammenfassung  相似文献   

First Results from the Soho Ultraviolet Coronagraph Spectrometer     

J. L. Kohl  G. Noci  E. Antonucci  G. Tondello  M. C. E. Huber  L. D. Gardner  P. Nicolosi  L. Strachan  S. Fineschi  J. C. Raymond  M. Romoli  D. Spadaro  A. Panasyuk  O. H. W. Siegmund  C. Benna  A. Ciaravella  S. R. Cranmer  S. Giordano  M. Karovska  R. Martin  J. Michels  A. Modigliani  G. Naletto  C. Pernechele  G. Poletto  P. L. Smith 《Solar physics》1997,175(2):613-644

The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R⊙ from Sun center. Initial observations of polar coronal holes and equatorial streamers are described. The observations include measurements of spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å, Mgx 625 Å, Fexii 1242 Å and several others. Intensities for Mgx 610 Å, Sixii 499 Å, and 520 Å, Sx 1196 Å, and 22 others have been observed. Preliminary results for derived H⁰, O⁵⁺, Mg₉₊, and Fe¹¹⁺ velocity distributions and initial indications of outflow velocities for O⁵⁺ are described. In streamers, the H⁰ velocity distribution along the line of sight (specified by the value at e^-1, along the line of sight) decreases from a maximum value of about 180 km s^-1 at 2 R⊙ to about 140 km s^-1 at 8 R⊙. The value for O⁵⁺ increases with height reaching a value of 150 km s^-1 at 4.7 R⊙. In polar coronal holes, the O⁵⁺ velocity at e^-1 is about equal to that of H⁰ at 1.7 R⊙ and significantly larger at 2.1 R⊙. The O⁵⁺ in both streamers and coronal holes were found to have anisotropic velocity distributions with the smaller values in the radial direction.  相似文献