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21.
The RHESSI Spectrometer 总被引:2,自引:0,他引:2
Smith D.M. Lin R.P. Turin P. Curtis D.W. Primbsch J.H. Campbell R.D. Abiad R. Schroeder P. Cork C.P. Hull E.L. Landis D.A. Madden N.W. Malone D. Pehl R.H. Raudorf T. Sangsingkeow P. Boyle R. Banks I.S. Shirey K. Schwartz Richard 《Solar physics》2002,210(1-2):33-60
RHESSI observes solar photons over three orders of magnitude in energy (3 keV to 17 MeV) with a single instrument: a set of
nine cryogenically cooled coaxial germanium detectors. With their extremely high energy resolution, RHESSI can resolve the
line shape of every known solar gamma-ray line except the neutron capture line at 2.223 MeV. High resolution also allows clean
separation of thermal and non-thermal hard X-rays and the accurate measurement of even extremely steep power-law spectra.
Detector segmentation, fast signal processing, and two sets of movable attenuators allow RHESSI to make high-quality spectra
and images of flares across seven orders of magnitude in intensity. Here we describe the configuration and operation of the
RHESSI spectrometer, show early results on in-flight performance, and discuss the principles of spectroscopic data analysis
used by the RHESSI software. 相似文献
22.
Alex Schwartz 《The Professional geographer》1987,39(2):166-172
An increasing number of studies of business start-ups, closings, and relocations rely on a single data base, DUNS Market Identifiers. This data file to U.S. business establishments provides researchers with essential information about individual firms and establishments. It also exhibits serveral idiosyncracies and requires careful consideration of the meaning of such basic terms as “location”and “firm.”Drawing from a recent survey of 500 New Jersey firms. I consider some of the methodological amd conceptual issues Dun and Bradstreet data pose for industrial location analysts. The Dun and Bradstreet listings exaggerate the exaggerate the incidence and magnitude of establishment openings and closing. 相似文献
23.
Krucker Säm Christe Steven Lin R.P. Hurford Gordon J. Schwartz Richard A. 《Solar physics》2002,210(1-2):445-456
The excellent sensitivity, spectral and spatial resolution, and energy coverage down to 3 keV provided by the Reuven Ramaty
High-Energy Solar Spectroscopic Imager mission (RHESSI) allows for the first time the detailed study of the locations and
the spectra of solar microflares down to 3 keV. During a one-hour quiet interval (GOES soft X-ray level around B6) on 2 May,
1:40–2:40 UT, at least 7 microflares occurred with the largest peaking at A6 GOES level. The microflares are found to come
from 4 different active regions including one behind the west limb. At 7′′ resolution, some events show elongated sources,
while others are unresolved point sources. In the impulsive phase of the microflares, the spectra can generally be fitted
better with a thermal model plus power law above ∼ 6–7 keV than with a thermal only. The decay phase sometimes can be fitted
with a thermal only, but in some events, power-law emission is detected late in the event indicating particle acceleration
after the thermal peak of the event. The behind-the-limb microflare shows thermal emissions only, suggesting that the non-thermal
power law emission originates lower, in footpoints that are occulted. The power-law fits extend to below 7 keV with exponents
between −5 and −8, and imply a total non-thermal electron energy content between 1026–1027 erg. Except for the fact that the power-law indices are steeper than what is generally found in regular flares, the investigated
microflares show characteristics similar to large flares. Since the total energy in non-thermal electrons is very sensitive
to the value of the power law and the energy cutoff, these observations will give us better estimates of the total energy
input into the corona. (Note that color versions of figures are on the accompanying CD-ROM.)
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022404512780 相似文献
24.
This paper examines the heating of asteroidal parent bodies by electrical induction during early solar evolution and prior to positioning of the sun onto the main sequence. Under the conditions assumed, which include a high initial solar spin rate, interplanetary electric fields of order 1 V/m would have existed in frames of reference comoving with the planets, leading to electrical heating from joule losses in the asteroidal interiors. The mechanism additionally requires the high plasma efflux characteristic of T Tauri objects and the presence of a circumstellar obscuration of the type commonly associated with early stellar objects. The proper combination of circumstellar obscuration, solar spin, solar wind flow, and starting planetary temperatures is shown to lead to asteroidal heating competitive with that found for a class of fossil radioactive species. The time dependence of the solar spin and plasma flow are shaped so as to be consistent with current views on the evolution to T Tauri objects and of the spin down of stars. Calculations also include cases of joint heating by fossil radionuclides and electrical induction, and show a complicated relationship due to the intrinsic nonlinearity of the electrical heating mechanism. Implications regarding the pre-main sequence dynamics of the sun are contained in the hypothesis of electrical heating if the contribution from radionuclides and gravitational accretion can be shown to be insufficient to account for the heating episode. Finally, some consequences of the mechanism applied to planets in the presence of an intense solar wind are considered. 相似文献
25.
Jessica R. Rodysill James M. Russell Satria Bijaksana Erik T. Brown La Ode Safiuddin Hilde Eggermont 《Journal of Paleolimnology》2012,47(1):125-139
Variations in the location and strength of convection in the Western Pacific Warm Pool (WPWP) have a profound impact on the
distribution and amount of global rainfall. Much of the variability in WPWP convection is attributed to variations in the
El Ni?o-Southern Oscillation, for which the long-term trends and forcing mechanisms remain poorly understood. Despite the
importance of WPWP convection to global climate change, we have very few paleohydrological reconstructions from the region.
Here we present a new paleolimnologic and paleohydrologic record spanning the past 1,400 years using a multi-proxy dataset
from Lake Logung, located in East Java, Indonesia that provides insights into centennial-scale trends in warm pool hydrology.
Organic matter δ13C data indicate that East Java became wetter over the last millennium until ca. 1800 Common Era (CE), consistent with evidence
for the southward migration of the Intertropical Convergence Zone (ITCZ) during this time. Superimposed on this long-term
trend are four decade- to century-scale droughts, inferred from organic matter δ13C and calcite abundance data. They are centered at 1030, 1550, 1830, and 1996 CE. The three more recent droughts correlate
with hydrologic anomalies documented in other proxy records from the WPWP region on both sides of the equator, and the two
most recent droughts correlate in time with historically documented periods of multiple, intense El Ni?o events. Thus, our
record provides strong evidence that century-scale hydrologic variability in this region relates to changes in the Walker
Circulation. Human activity within the lake catchment is apparent since 1860 CE. 相似文献
26.
C. Sigismondi D. W. Dunham K. Guhl S. Andersson H. Bode O. Canales P. Colona O. Farago M. Fernández-Ocaña A. Gabel M. Haupt C. Herold R. Nugent P. Oliva M. Patel C. Perello W. Rothe J. Rovira T. Schaefer C. Schnabel D. Schwartz A. Selva W. Strickling A. Tegtmeier C. Tegtmeier B. Thome W. H. Warren 《Solar physics》2009,258(2):191-202
In the annular or total eclipses of 3 October 2005, 29 March 2006, 22 September 2006, and 1 August 2008, observational campaigns
were organized to record the phenomenon of Baily’s beads. These campaigns were internationally coordinated through the International
Occultation Timing Association (IOTA) at both its American and European sections. From the stations in the northern and southern
zones of grazing eclipse, the eclipses have been recorded on video. Afterward, as many beads as possible have been identified
by analyzing the video data of each observing station. The atlas presented in this paper includes 598 data points, obtained
by 23 observers operating at 28 different observing stations. The atlas lists the geographic positions of the observing stations
and the observed time instants of disappearance or reappearance of beads, identified by an angle measured relative to the
Moon’s axis of rotation. The atlas will serve as a basis for determining the solar diameter.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
27.
Yan-Chun Zhang Caroline P. Slomp Hilde F. Passier 《Geochimica et cosmochimica acta》2009,73(22):6716-6726
This study focuses on denitrification in a sandy aquifer using geochemical analyses of both sediment and groundwater, combined with groundwater age dating (3H/3He). The study sites are located underneath cultivated fields and an adjacent forested area at Oostrum, The Netherlands. Shallow groundwater in the region has high nitrate concentrations (up to 8 mM) due to intense fertilizer application. Nitrate removal from the groundwater below cultivated fields correlates with sulfate production, and the release of dissolved Fe2+ and pyrite-associated trace metals (e.g. As, Ni, Co and Zn). These results, and the presence of pyrite in the sediment matrix within the nitrate removal zone, indicate that denitrification coupled to pyrite oxidation is a major process in the aquifer. Significant nitrate loss coupled to sulfate production is further confirmed by comparing historical estimates of regional sulfate and nitrate loadings to age-dated groundwater sulfate and nitrate concentrations, for the period 1950-2000. However, the observed increases in sulfate concentration are about 50% lower than would be expected from complete oxidation of pyrite to sulfate, possibly due to the accumulation of intermediate oxidation state sulfur compounds, such as elemental sulfur. Pollutant concentrations (NO3, Cl, As, Co and Ni) measured in the groundwater beneath the agricultural areas in 1996 and 2006 show systematic decreases most likely due to declining fertilizer use. 相似文献
28.
Leigh Schwartz 《GeoJournal》2009,74(3):265-274
As geographers begin investigating the imaginative geographies of media spaces, attention is drawn to the landscapes of interactive
media. The virtual environments of video games continue to grow in complexity and use, and questions remain as to the experience
of the users of the designed environments. Focusing specifically on messages and metaphors in written representations, this
paper investigates the changing experience of gamers through time and place by examining the Suikoden fantasy series. Beginning
with the adaptation of the Chinese classic Shui Hu Zhuan into Suikoden in 1996, continuing to the release of Suikoden V 10 years later, the virtual environments of the Suikoden series are embedded with mythological and cultural messages about
Self and Other. This paper utilizes visual and textual analysis to examine these changing representations over time and place
in terms of the experience of these ideological messages by the players of this series. 相似文献
29.
Pierre Lanari Yann Rolland Stéphane Schwartz Olivier Vidal Stéphane Guillot Pierre Tricart Thierry Dumont 《地学学报》2014,26(2):130-138
Pressure–Temperature–time (P–T–t) estimates of the syn‐kinematic strain at the peak‐pressure conditions reached during shallow underthrusting of the Briançonnais Zone in the Alpine subduction zone was made by thermodynamic modelling and 40Ar/39Ar dating in the Plan‐de‐Phasy unit (SE of the Pelvoux Massif, Western Alps). The dated phengite minerals crystallized syn‐kinematically in a shear zone indicating top‐to‐the‐N motion. By combining X‐ray mapping with multi‐equilibrium calculations, we estimate the phengite crystallization conditions at 270 ± 50 °C and 8.1 ± 2 kbar at an age of 45.9 ± 1.1 Ma. Combining this P–T–t estimate with data from the literature allows us to constrain the timing and geometry of Alpine continental subduction. We propose that the Briançonnais units were scalped on top of the slab during ongoing continental subduction and exhumed continuously until collision. 相似文献
30.
Determining concentration fields of tracer plumes for layered porous media in flow-tank experiments 总被引:1,自引:0,他引:1
In the laboratory, computer-assisted image analysis provides an accurate and efficient way to monitor tracer experiments.
This paper describes the determination of detailed temporal concentration distributions of tracers in a flow-tank experiment
by analyzing photographs of plumes of Rhodamine dye through the glass wall of the tank. The methodology developed for this
purpose consists of four steps: (1) digitally scanning black and white negatives obtained from photographs of the flow–tank
experiment; (2) calibrating and normalizing each digitized image to a standard optical-density scale by determining the relation
between the optical density and pixel value for each image; (3) constructing standard curves relating the concentration in
an optical density from five experimental runs with predetermined concentrations (2–97 mg/L); and (4) converting the optical
density to concentration. The spatial distribution of concentration for two photographs was determined by applying these calibration
and conversion procedures to all pixels of the digitized images. This approach provides an efficient way to study patterns
of plume evolution and transport mechanisms.
Received, March 1998 Revised, September 1998 Accepted, October 1998 相似文献