Vibrational temperature and excess vibrational energy of molecular nitrogen in the ground state derived from N₂⁺ emission bands in aurora     

V.A. Vlaskov  K. Henriksen 《Planetary and Space Science》1985,33(2):141-145

A method to estimate the vibrational distribution for N₂ in the ground state by using the intensities of allowed transitions, excited by direct particle impact, is developed. The method is tested on a rather limited amount of data, but the results seem to be reasonable and indicate that 10% of the particle energy is stored as vibrational energy by N₂ molecules, and that the vibrational temperature is increased more than 1000K relative to the kinetic temperature on the dayside.  相似文献   

BiL(E) and the Hubble sequence: A new theory of galaxies     

R. N. Henriksen  M. Reinhardt 《Astrophysics and Space Science》1977,49(1):3-39

We show that magnetic fields can be important in the formation and evolution of galaxies and that they might be indeed the missing parameters to explain the Hubble sequence. We use the self-consistent theory of spiral magneto-hydrodynamic flow developed by Henriksen and co-workers over the last few years. Section 2 is a short outline of this theory, where we introduce and justify the simplifying assumptions and list the relevant physical relations.Section 3 deals mainly with the formation of galactic nuclei and proto-galaxies. We envisage the following scenario: The first objects to form after recombination in a canonical hot big-bang universe with turbulence and magnetic fields have masses of order 10⁹ M . In a violent burst of activity—possible mechanisms are discussed—they ionize the surrounding medium, raising the Jeans mass to a galactic scale, and becoming the condensation seeds of galaxies. The subsequent evolution of these nuclei, including recurrent activity, is discussed in some detail.The remaining sections—in principle independent from Section 3—deal with galactic morphology as the result of the collapse of a hot, spherical, rotating proto-galaxy endowed with a regular magnetic field. The main parameter determining the morphological type is the anglei between the magnetic field and the angular momentum. Smalli give rise to Sc galaxies, largei to ellipticals (Section 4), and intermediate values to the rest of the Hubble sequence. Subtypes are produced by variation of the strength of the magnetic field in comparison to the angular momentum. Thus relatively strong fields will produce triaxial ellipticals, barred spirals and irregulars.Some of the observationally testable predictions of our theory concern: the energetics, duration and frequency of nuclear activity, the absence of dwarf spiral galaxies, rigidly rotating nuclear regions in galaxies, the mass and structure of galactic halos, leading and trailing spiral arms and their pitch angle, the bulge-to-disc ratio, the frequency distribution of morphological types, and the warping of galactic discs. Moreover some seemingly pathological galaxies like NGC 2685 and 4314 find a simple explanation.On leave of absence from Astronomisches Institut der Ruhr-Universität Bochum, F.R.G.  相似文献   

Dynamic Holocene glacial history of St. Jonsfjorden,Svalbard     

Wesley R. Farnsworth  Ólafur Ingólfsson  Riko Noormets  Lis Allaart  Helena Alexanderson  Mona Henriksen  Anders Schomacker 《Boreas: An International Journal of Quaternary Research》2017,46(3):585-603

Evidence of a dynamic Holocene glacial history is preserved in the terrestrial and marine archives of St. Jonsfjorden, a small fjord‐system on the west coast of Spitsbergen, Svalbard. High‐resolution, remotely sensed imagery from marine and terrestrial environments was used to construct geomorphological maps that highlight an intricate glacial history of the entire fjord‐system. The geomorphology and stratigraphy indicate an early Holocene local glacier advance constrained to the Lateglacial–early Holocene transition. Identification and ¹⁴C dating of the thermophilous bivalve mollusc Modiolus modiolus to 10.0±0.12 cal. ka BP suggest a rapid northward migration of the species shortly after deglaciation. Further evidence enhances the understanding of the onset and subsequent climax of the Neoglacial‐Little Ice Age in inner St. Jonsfjorden. The present‐day terminus of Osbornebreen, the dominating glacier system in St. Jonsfjorden, is located over 8.5 km up‐fjord from its Neoglacial maximum extent. Cross‐cutting relationships suggest subsequent advances of all the smaller glaciers in the area following the break‐up of Osbornebreen. Glacial deposits, landforms and their cross‐cutting relationships observed in both terrestrial and marine settings imply a complex and highly dynamic environment through the later part of the Holocene.  相似文献   

The Ardón L6 ordinary chondrite: A long‐hidden Spanish meteorite fall     

Josep M. Trigo‐Rodríguez  Jordi Llorca  Mona Weyrauch  Addi Bischoff  Carles E. Moyano‐Cambero  Klaus Keil  Matthias Laubenstein  Andreas Pack  José María Madiedo  Jacinto Alonso‐Azcárate  My Riebe  Rainer Wieler  Uli Ott  Mar Tapia  Narcís Mestres 《Meteoritics & planetary science》2014,49(8):1475-1484

We report and describe an L6 ordinary chondrite fall that occurred in Ardón, León province, Spain (longitude 5.5605°W, latitude 42.4364°N) on July 9th, 1931. The 5.5 g single stone was kept hidden for 83 yr by Rosa González Pérez, at the time an 11 yr old who had observed the fall and had recovered the meteorite. According to various newspaper reports, the event was widely observed in Northern Spain. Ardón is a very well‐preserved, fresh, strongly metamorphosed (petrologic type 6), and weakly shocked (S3) ordinary chondrite with well‐equilibrated and recrystallized minerals. The mineral compositions (olivine Fa_23.7±0.3, low‐Ca pyroxene Fs_20.4±0.2Wo_1.5±0.2, plagioclase An_10.3±0.5Ab_84.3±1.2), magnetic susceptibility (log χ = 4.95 ± 0.05 × 10^?9 m³ kg^?1), bulk density (3.49 ± 0.05 g   cm^?3), grain density (3.58 ± 0.05 g   cm^?3), and porosity (2.5 vol%) are typical for L6 chondrites. Short‐lived radionuclides confirm that the meteorite constitutes a recent fall. The ²¹Ne and ³⁸Ar cosmic ray exposure ages are both about 20–30 Ma, similar to values for many other L chondrites. The cosmogenic ²²Ne/²¹Ne ratio indicates that preatmospheric Ardón was a relatively large body. The fact that the meteorite was hidden in private hands for 83 yr makes one wonder if other meteorite falls may have experienced the same fate, thus possibly explaining the anomalously low number of falls reported in continental Spain in the 20th century.  相似文献   

LINKING AMERICAN EMPIRE WITH THE AGS     

Mona Domosh 《Geographical review》2012,102(4):545-547

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Assessing groundwater vulnerability using GIS-based DRASTIC model for Ahmedabad district,India     

Mona Khakhar  Jayesh P. Ruparelia  Anjana Vyas 《Environmental Earth Sciences》2017,76(12):440

The present research aims to derive the intrinsic vulnerability of groundwater against contamination using the GIS platform. The study applies DRASTIC model for Ahmedabad district in Gujarat, India. The model uses parameters like depth, recharge, aquifer, soil, topography, vadose zone and hydraulic conductivity, which depict the hydrogeology of the area. The research demonstrates that northern part of district with 46.4% of area is under low vulnerability, the central and southern parts with 48.4% of the area are under moderate vulnerability, while 5.2% of area in the south-east of district is under high vulnerability. It is observed from the study that lower vulnerability in northern part may be mostly due to the greater depth of vadose zone, deeper water tables and alluvial aquifer system with minor clay lenses. The moderate and high vulnerability in central and southern parts of study area may be due to lesser depth to water tables, smaller vadose zone depths, unconfined to semi-confined alluvial aquifer system and greater amount of recharge due to irrigation practices. Further, the map removal and single-parameter sensitivity analysis indicate that groundwater vulnerability index has higher influence of vadose zone, recharge, depth and aquifer parameters for the given study area. The research also contributes to validating the existence of higher concentrations of contaminants/indicators like electrical conductivity, chloride, total dissolved solids, sulphate, nitrate, calcium, sodium and magnesium with respect to groundwater vulnerability status in the study area. The contaminants/indicators exceeding the prescribed limits for drinking water as per Indian Standard 10500 (1991) were mostly found in areas under moderate and high vulnerability. Finally, the research successfully delineates the groundwater vulnerability in the region which can aid land-use policies and norms for activities related to recharge and seepage with respect to existing status of groundwater vulnerability and its quality.  相似文献   

Distribution of gamma-ray bursts in halo neutron star-comet models     

M. G. Higgins  R. N. Henriksen 《Astrophysics and Space Science》1995,231(1-2):419-422

The motions of comets and neutron stars have been integrated over five billion years in the Galactic potential to determine a gamma-ray burst distribution, presuming that bursts are the result of interactions between these two families of objects. The comets originate in two distinct populations - one from ejection by stars in the Galactic disk, and the other from ejection by stars in globular clusters. No choice of the free parameters resulted in agreement with both the isotropy data and the log(N >F)-log(F) data.  相似文献   

Ground-based observations of O₂ (b¹Σ⁺_g−X³Σ⁻_g) atmospheric bands in high latitude auroras     

K. Henriksen  G.G. Sivjee  C.S. Deehr  H.K. Myrabø 《Planetary and Space Science》1985,33(1):119-125

Analysis of observed spectrograms is based on comparison with synthetic spectra. The O₂(b¹Σ⁺_g?X³Σ^?_g Atm. (1,1) band in high latitude auroras observed from the ground is found to be the strongest in the Δv = 0 sequence. It is enhanced with altitude relative to the N₂ 1P(2, 0)and N⁺₂ M(2,0) bands, but the O₂ Atm. (2, 2) band has an unexpected low intensity. The range of rotational temperatures of the O₂ Atm. bands varies from approx. 200 to above 500 K which indicates that the altitude of the centroid of the emission region varies from about 100 km to the F-region. The highest temperature is found in the midday aurora associated with the magnetospheric cusp. Conspicuous relative variations between the intensities of N₂ and O₂ spectra are documented, but a satisfactory explanation of the variety is not given. Deviations of the observed O₂ Atm. band intensities from the vibrational intensity distribution predicted by Franck-Condor factors indicate that the excitation of the O₂ Atm. bands in aurora is not mainly due to particle impact on O₂, and the contribution due to energy transfer from hot O(¹D) atoms has to be found in future research.  相似文献   

Advection-Dispersion Analysis of Solute Transport in Undisturbed Soil Monoliths     

Karsten Høgh Jensen  Georgia Destouni  Mona Sassner 《Ground water》1996,34(6):1090-1097

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Laboratory studies on the removal of phosphates from sewage by the coagulation process (Part 2)     

Arne Henriksen 《Aquatic Sciences - Research Across Boundaries》1963,25(2):380-396

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