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Browsing Fakultet for naturvitenskap og teknologi by Title
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Godtliebsen, Fred; Holmström, L.; Miettinen, A.; Erästö, P.; Divine, Dmitry V; Koc, Nalan (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: In this paper, we study how sea surface temperature variations in the North Atlantic and the Norwegian Sea are correlated with the climate in the Northern Hemisphere in late Holocene. The analysis is performed by testing statistical hypotheses through novel scale space methodologies. In late Holocene, the proposed techniques reveal that the climate development in the subpolar North Atlantic has been incoherent with the development in the Norwegian Sea and the Northern Hemisphere. A prominent discrepancy between the three analyzed series is identified for the periods associated with the Medieval Warm Period and the Little Ice Age. A divergence between the oceanic series and the global Northern Hemisphere temperature estimate detected in the twentieth century is in line with the inferred imprint of recent climate change which suggests accentuated warming, in particular over continental regions. Overall, the results obtained by scale space analysis underscore the significance of the northern North Atlantic in shaping the climate globally, mainly through changes in the strength and structure of the Atlantic meridional overturning circulation. URI: http://hdl.handle.net/10037/4569 File(s) in this item: 1
article.pdf (371.3Kb) -
Rüther, Denise Christina (Doctoral thesis; Doktorgradsavhandling, 01-Mar-2012)[+][-]
Abstract: The scope of this PhD thesis is twofold: Firstly, processes, patterns and timing of the last deglaciation in the Barents Sea are reconstructed and secondly, depositional conditions on the Barents shelf during Holocene are elucidated. This cumulative PhD thesis encompasses an introductory part and five papers - three as first-author and two as co-author. Three papers are focused on the most prominent geomorphological freature of the western Barents shelf, 850 km long cross-shelf trough Bjørnøyrenna (The Bear Island Trough). One detailed study examines processes and timing of the first step of glacial retreat in outer Bjørnøyrenna and establishes a minimum age of 17 cal ka for initial deglaciation. A second study focuses on a grounding line system in uppermost Bjørnøyrenna, witnessing a surge-type readvance towards the final collapse of the marine-based Barents Sea Ice Sheet. A third study focuses on contrasting ice stream flow regimes and processes observed from glacial maximum over initial deglaciation towards final deglaciation. Two additional studies are located in the relatively small formerly glaciated trough Kveithola, north-west of Bjørnøya (Bear Island). The first focuses on the most recent deglaciation history and establishes an indirect deglaciation age for Spitsbergenbanken 14.2-13.9 cal ka ago. The other reconstructs the complex glacial retreat through Kveithola and associated processes based on geophysical data. As a whole, this PhD thesis improves existing chronology during deglaciation and Holocene for the Barents Sea, advances existing depositional models of ice-marginal and deglacial processes as well as it adds to established conceptional models of glacial retreat. While presented Holocene data is less conclusive, it might create the awareness that the large Storegga tsunami at 8.2 cal ka may have had an erosional impact on shelf sediments and thereby motivate further research. Description: The papers of this thesis are not available in Munin:
1. Rüther, D. C., Mattingsdal, R., Andreassen, K., Forwick, M. and Husum, K.: 'Seismic architecture and sedimentology of a major grounding zone system deposited by the Bjørnøyrenna Ice Stream during Late Weichselian deglaciation', Quaternary Science Reviews (2011) vol.30:2776-2792. Available at http://dx.doi.org/10.1016/j.quascirev.2011.06.011
2. Rüther, D. C., Bjarnadóttir, L. R. Junttila, J., Husum, K., Rasmussen, T., Lucchi, R. G. and Andreassen, K.: 'Pattern and timing of the north-western Barents Sea Ice Sheet deglaciation and indications of episodic Holocene deposition' (accepted paper in Boreas).
3. Bjarnadóttir, L. R., Rüther, D. C., Winsborrow, M. C. M. and Andreassen, K.: 'Grounding line dynamics during the last deglaciation of Kveithola, W Barents Sea, as revealed by seabed geomorphology and shallow seismic stratigraphy' (submitted manuscript to Boreas).
4. Andreassen, K., Winsborrow, M. C. M., Bjarnadóttir, L. R. and Rüther, D. C.: 'Landform assemblage from the collapse of a marine-based ice stream' (submitted manuscript to Geology).
5. Rüther, D. C., Andreassen, K. and Winsborrow, M. C. M.: 'Changing ice stream flow regimes during the last deglaciation of Bjørnøyrenna, western Barents Sea' (manuscript)URI: http://hdl.handle.net/10037/3876 File(s) in this item: 1
thesis.pdf (786.4Kb) -
Lorentzen, Dag Arne; Lunde, June; Ogawa, Y; Gustavsson, B; Ogawa, Yasunobu; Løvhaug, U.P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
Abstract: In this paper we present Naturally Enhanced Ion Acoustic Lines (NEIALs) observed with the EISCAT Svalbard Radar (ESR). For the first time, long sequences of NEIALs are recorded, with more than 50 events within an hour, ranging from 6.4 to 140 s in duration. The events took place from ~08:45 to 10:00 UT, 22 January 2004. We combine ESR data with observations of optical aurora by a meridian scanning photometer at wavelengths 557.7, 630.0, 427.8, and 844.6 nm, as well as records from a magnetometer and an imaging riometer. The large numbers of observed NEIALs together with these additional observations, enable us to characterise the particle precipitation during the NEIAL events. We find that the intensities in all optical lines studied must be above a certain level for the NEIALs to appear. We also find that the soft particle precipitation is associated with the down-shifted shoulder in the incoherent scatter spectrum, and that harder precipitation may play a role in the enhancement of the up-shifted shoulder. The minimum energy flux during NEIAL events found in this study was ~3.5 mW/m2 and minimum characteristic energy around 50 eV. URI: http://hdl.handle.net/10037/3126 File(s) in this item: 1
article.pdf (7.856Mb) -
Lunde, June; Løvhaug, Unni Pia; Gustavsson, Björn Johan (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)[+][-]
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Lunde, June (Doctoral thesis; Doktorgradsavhandling, 26-Nov-2009)[+][-]
Abstract: The motivation behind this thesis has been to study particle precipitation from the Sun into the Earth’s upper atmosphere and its effects on selected ionospheric phenomena. Particles from the solar wind can enter the Earth's magnetosphere through magnetic merging, either at the sub-solar point, or at higher latitudes, depending on the configuration of the interplanetary magnetic field. This interaction can be studied from the ground at Svalbard, due to its fortuitous location beneath the magnetospheric cusp region on the dayside, and its location inside the polar cap during night-time. It has been studied how these precipitating particles act on the aurora and ion-acoustic waves in the ionized part of the atmosphere. The studies have been conducted using various methods, including extracting data from databases, running different experiments and building new instrumentation. The latter was a radiation detector for measuring Bremsstrahlung X-rays. The main instrument used for this study has been the EISCAT (European Incoherent SCATtering) radar located at Svalbard, together with an assortment of other ground based instruments such as photometers, riometers and magnetometers. In addition, particle instruments onboard satellites have been used as well as an X-ray instrument mounted on a balloon launched from Longyearbyen. Primarily, it is the effect of particle precipitation on large ion-acoustic waves that has been studied. These waves can be observed by advanced radar facilities, both from Svalbard and Tromsø (EISCAT) in the form of spectra known as natural enhanced ion acoustic lines (NEIALs). It has been found that the most energetic particle precipitation causes ion-acoustic waves which mainly propagate downward, while the less energetic part of the particle precipitation is related to ion-acoustic waves which propagate upward. In this project, large ion-acoustic waves have been discovered during night-time at very high latitudes where they were not expected to occur. Previously, these phenomena have only been observed during daytime at Svalbard. Furthermore, in this work, the infrared atomic oxygen emission line (844.6 nm) has been introduced as a new possible method to detect NEIALs in optical data. Particle precipitation sometimes cause flickering aurora, hence intensity variation and the apparent motion of flickering spots in the aurora have been studied. Finally, precipitating particles typically consists of electrons and ions, and in this study, an example is given on of how the merging of the Earth’s and Sun’s magnetic fields guide the precipitation. Description: Papers 2 and 4 are not available in Munin:
2. T. Grydeland, B. Gustavsson, L. Baddeley, J. Lunde, and E. M. Blixt: 'Conditional integration of Incoherent Scattering in relation to flickering aurora', Journal of Geophysical Research (2008), vol.113, A08305, 8pp. Available at http://dx.doi.org/doi:10.1029/2008JA013039
4. B. Gustavsson, J. Lunde, and E. M. Blixt: 'Optical observations of flickering aurora and its spatio-temporal characteristics', Journal of Geophysical Research (2008), vol.113, A12317, 8pp. Available at http://dx.doi.org/10.1029/2008JA013515URI: http://hdl.handle.net/10037/4221 File(s) in this item: 4
paper_1.pdf (2.832Mb)paper_3.pdf (14.41Mb)paper_5.pdf (7.665Mb)thesis.pdf (7.645Mb) -
Asplin, Jo; Johansen, Dag (Research report; Forskningsrapport, Jun-1995)[+][-]
Abstract: Volume rendering is a useful but cpu-intensive method for visualizing large scalar fields. The time to render a single image may be reduced by parallel processing. This paper reports on performance experiments with the StormView volume renderer, which is parallelized on a set of 57 MIPS / 17 MFLOPS workstations connected by a 10 Mbps Ethernet. For certain user patterns, we show that our parallelization exhibits substantial speedups. We compare the performance of a dynamic and a static load balancing algorithm. URI: http://hdl.handle.net/10037/384 File(s) in this item: 1
report.pdf (383.3Kb) -
Kvalnes, Aage; Renesse, Robbert van; Johansen, Dag (Research report; Forskningsrapport, 10-Jan-2003)[+][-]
Abstract: Vortex is a new multiprocessor operating system kernel intended for emerging Internet service applications. The architecture is based on SEDA's staged computational model. Vortex provides mechanisms for performance isolation and dynamic adaptation. Performance results validate that the resource control mechanisms of Vortex are effective, and that Vortex significantly outperforms Linux on single-threaded web servers. The paper concludes with a description of how we plan to support a highly scalable event stream filtering service. URI: http://hdl.handle.net/10037/399 File(s) in this item: 1
report.pdf (174.8Kb) -
Brodal, Eivind; Melandsø, Frank; Jacobsen, Svein Ketil (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: New designs of high-resolution ultrasonic imaging systems that operate in the 30–100MHz region, for example, those based on linear transducer systems, are currently being investigated for medical purposes. Acoustic waves with frequencies in this range can detect microscopic structures in human tissue but will typically only penetrate a few mm because of large attenuation. However, this is sufficient for a diagnostic ultrasound scan of human skin. The signal-to-noise ratio and the focusing properties of the scanner are critical factors in dermatology, which are determined by the transducer design. A linear pulsed PVDF transducer array with a center frequency around 45MHz is studied by applying numerical simulations, based on the finite element method (FEM), of this electromechanical system. Tx-beamforming properties of linear arrays with one, three, five, and seven active elements are investigated at different depths. The image quality obtained from synthetic Rx-beamforming, using responses from five electrodes, is estimated from reconstructed images of 25–100 μm thick objects. The axial and lateral resolutions of these images are found to be similar with the Tx-beamforming resolution parameters estimated from the time-derivative of the pressure beams. URI: http://hdl.handle.net/10037/3941 File(s) in this item: 1
article.pdf (4.220Mb) -
Nozawa, S.; Hall, Chris; Meek, C.E.; Manson, A.H.; Luo, Yi (Journal article; Peer reviewed, 2003)[+][-]
Abstract: It is possible for medium-frequency (MF) radar systems to estimate kinetic energy dissipation rates by measuring signal fading times. Here, we present approximately 5 years of such results from Tromsø (69° N, 19° E) and in particular, investigate the periodicities present at different altitudes in the regime 80 to 100 km. We detect the known annual variation in the mesosphere and the semiannual variation on the lower thermosphere. In addition, other features are observed including terannual and ~ 27-day components in the lower thermosphere. URI: http://hdl.handle.net/10037/577 File(s) in this item: 1
article.pdf (691.3Kb) -
Dillema, Feike W.; Stabell-Kulø, Tage (Research report; Forskningsrapport, May-2002)[+][-]
Abstract: Pesto aims at providing highly available and secure storage for longlived data to mobile users roaming into untrusted environments. Security in Pesto encompasses the following three aspects: availability, safety, and privacy. A mechanism supporting one aspect may adversely affect another. For example, replication may increase availability but complicates supporting confidentiality, and simply encrypting data for confidentiality may defeat the whole purpose of replication. We show that an integral approach to these aspects leads to considerable savings in overall system complexity, and thus to a more secure system. In Pesto, users may specify different levels of trust in different parts of the infrastructure. In particular, a user may trust a node to merely store (encrypted) data, and/or to distribute replicas to other nodes on his behalf, and/or he may trust a node to enforce access control on his behalf to his (plaintext) content. This report gives an overview of the main security mechanisms that makes this separation of concerns possible. We present its novel encryption framework and its trust management and discuss how it can be used to build distributed infrastructures with advanced security and safety properties. URI: http://hdl.handle.net/10037/364 File(s) in this item: 1
report.pdf (135.8Kb) -
Priyatkina, Nadezda (Master thesis; Mastergradsoppgave, 31-Jan-2013)[+][-]
Abstract: The studied mafic-ultramafic rock association occurs within Archean tonalitic gneisses and metasupracrustal suites of the Astridal belt belonging to the West Troms Basement Complex in the northwestern part of the Senja Island. The rock association appears in lens-shaped bodies, up to 200 m long, which are oriented conformal to the major metamorphic fabric of the host rock. The rock association is made up by interlayered units of green spinel-bearing olivine orthopyroxene-hornblendite, hornblende peridotite, olivine hornblendite, hornblendite and amphibolite (metagabbroic rock). Microscope studies and whole rock geochemical data indicate that the ultramafic rocks represent a single magmatic series of mafic and ultramafic olivine-amphibole cumulates, which have been significantly affected by metamorphism. Igneous mineral and whole rock trace element data indicate MORB affinity of the cumulates and suggest their emplacement in oceanic rift or rifted continental margin setting. The studied cumulates may represent a crustal remnant of the Paleoproterozic Svecofennian ocean. The rocks were metamorphosed together with the supracrustal suites of the Astridal belt during the major Svecofennian event about 1.74 Ga ago as indicated by a U-Pb age of metamorphic zircons from the metagabbroic rock belonging to the studied suite. URI: http://hdl.handle.net/10037/4843 File(s) in this item: 1
thesis.pdf (13.80Mb) -
Gjerløw, Eirik (Master thesis; Mastergradsoppgave, 15-Nov-2008)[+][-]
Abstract: Formålet med denne oppgaven er å gjøre petrologiske og petrografiske undersøkelser av en mafisk linse på Sandøya i vest-Troms for å rekonstruere metamorfe trykk og temperaturforhold, samt å gjøre dateringer for å utrede alderen på metamorfosen(e). Linsa ligge blottlagt ved havet ved Mjølvika på Sandøya. Kjernen er tilnærmet udeformert og består av en en massiv granatførende bergart med en grønn grunnmasse. Graden av deformasjon og hydrering tiltar mot marginene mot de båndede gneisene som omgir linsa. Den mafiske linsa er også kuttet av en liten felsisk gang, dateringer av denne gangen vil kunne gi minimumsalder på den mafiske linsa. Resultatene er basert på dateringer og metamorf utvikling Aldre på 1776,6 ± 1,1 Ma, 1774,4 ± 1,7, 1777 ± 12 Ma tolkes til å representere granulittfacies metamorfose og intrusjon av den kuttende felsiske gangen og det antaes at denne gangen er dannet ved partiell oppsmelting av omkringliggende bergarter. Ut fra strukturer og mineralkjemiske analyser tolkes det til at det er minst 5 forskjellige faser av metamorfose: Stadium 1 er høytrykks granulittfacies med trykk og temperaturforhold på 715-922 ºC og 1,1-1,43 Gpa. Stadium 2 er granulittfacies med trykk og temperaturverdier på 710-715 ºC og 0,51-0,92 GPa. Stadium 3 er grønnskiferfacies. Stadium 4 er amfibolittfacies med trykk og temperaturverdier på 595-660 ºC og 0,17-0,62 Gpa. Stadium 5 er grønnskiferfacies. URI: http://hdl.handle.net/10037/1657 File(s) in this item: 1
thesis.pdf (20.95Mb) -
Grydeland, Tom; Sullivan, J.M.; Ivchenko, N.; Blixt, Erik Mårten; Lockwood, M.; Lanchester, B.S. (Journal article; Peer reviewed, 20-Sep-2006)[+][-]
Abstract: The link between natural ion-line enhancements in radar spectra and auroral activity has been the subject of recent studies but conclusions have been limited by the spatial and temporal resolution previously available. The next challenge is to use shorter sub-second integration times in combination with interferometric programmes to resolve spatial structure within the main radar beam, and so relate enhanced filaments to individual auroral rays. This paper presents initial studies of a technique, using optical and spectral satellite signatures, to calibrate the received phase of a signal with the position of the scattering source along the interferometric baseline of the EISCAT Svalbard Radar. It is shown that a consistent relationship can be found only if the satellite passage through the phase fringes is adjusted from the passage predicted by optical tracking. This required adjustment is interpreted as being due to the vector between the theoretical focusing points of the two antennae, i.e. the true radar baseline, differing from the baseline obtained by survey between the antenna foot points. A method to obtain a measurement of the true interferometric baseline using multiple satellite passes is outlined. URI: http://hdl.handle.net/10037/549 File(s) in this item: 1
article.pdf (800.0Kb) -
Brekke, Asgeir; Blagoveshchenskaya, N. F.; Carlson, H. C.; Kornienko, V. A.; Borisova, T. D.; Rietveld, M. T.; Yeoman, T. K. (Journal article; Tidsskriftartikkel; Peer reviewed, 08-Jan-2009)[+][-]
Abstract: Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency was just below the third electron gyro harmonic frequency, while both the HF pump beam and UHF radar beam were directed towards the magnetic zenith (MZ). The HF pump-induced phenomena were diagnosed with several instruments: the bi-static HF radio scatter on the London- Tromsø-St. Petersburg path, the CUTLASS radar in Hankasalmi (Finland), the European Incoherent Scatter (EISCAT) UHF radar at Tromsø and the Tromsø ionosonde (dynasonde). The results show thermal electron excitation of the HF-induced striations seen simultaneously from HF bi-static scatter and CUTLASS radar observations, accompanied by increases of electron temperature when the heater frequency was near and then above the critical frequency of the F2 layer by up to 0.4 MHz. An increase of the electron density up to 25% accompanied by strong HF-induced electron heating was observed, only when the heater frequency was near the critical frequency and just below the third electron gyro harmonic frequency. It is concluded that the combined effect of upper hybrid resonance and gyro resonance at the same altitude gives rise to strong electron heating, the excitation ofstriations, HF ray trapping and extension of HF waves to altitudes where they can excite Langmuir turbulence and fluxes of electrons accelerated to energies that produce ionization. Description: This is the publisher’s version/PDF (published in Annales Geophysicae, an open access journal of the European Geosciences Union) URI: http://hdl.handle.net/10037/2384 File(s) in this item: 1
angeo-27-131-2009.pdf (1.432Mb) -
von Garnier, Christophe; Stunitz, Holger; Decker, Michael; Battegay, Edouard; Zeller, Andreas (Journal article; Tidsskriftartikkel, 2008)[+][-]
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Janocko, Michal (Master thesis; Mastergradsoppgave, 22-Feb-2008)[+][-]
Abstract: The pinch-out geometry of large sandbodies, such as fluvial or turbiditic palaeochannel margins and deltaic sand wedges, is of a crucial importance to the evaluation of many stratigraphic hydrocarbon traps and can generally be recognized in extensive outcrops or high-resolution seismic sections. Far more difficult to recognize and model are the digitate, feather-edge pinchouts of successions composed of sheet-like sandstone beds, such as turbidite lobes or shore-derived mid-shelf tempestites, where the individual beds may peter out at highly varied basinward distances. Both turbidites and tempestites are expected to pinch out seawards, but their actual thinning rates and pinchout geometries are little-known and unpredictable. Can the lateral variation of sheet-like bed characteristics be empirically defined? In the present pilot study, more than 3750 closely-spaced (2-10 m lateral spacing) measurements of the lateral thickness changes in 146 turbidite and tempestite beds have been collected over lateral outcrop distances of up to 640 m. Turbidites have been measured in the Miocene Marnoso Arenacea Formation of the Northern Apennines, Italy, and the Late Cretaceous Akveren Formation of the Central Pontides, north-central Turkey, with supplementary smaller datasets from the Eocene Kusuri Formation of the Central Pontides and the Miocene Monte Fumaiolo Formation of the Northern Apennines. Tempestites have been measured in the late Miocene Karpuzçay Formation in the Manavgat Basin of Central Taurides, south-western Turkey. The spatial direction of bed thinning relative to the palaeocurrent direction has been taken into account. The datasets show that both turbidites and tempestites have a log-normal thickness frequency distribution, a trend that has been also commonly reported from bed-to-bed thickness measurements of vertical successions. In terms of an exceedence frequency plot with logarithmic scales, the log-normal distribution can be approximated by straight-line segments, which means that the bed thicknesses are self-similar (fractal) within their particular ranges. The statistical method of least-square regression has been used to identify lateral bed-thinning trends, which appear to be consistent for each genetic category of beds, but dependent upon the bed thickness range – as the downflow bed thinning rate apparently changes significantly with the bed thickness. Assuming the bed segments measured in outcrop sections represent downflow-thinning segments of unconfined (non-ponded) basin-plain turbidites and shelf tempestites, their thinning rates can be stacked together according to the local bed-thickness ranges to represent the pinchout geometry of a whole single bed. The stacking of local trends into a laterally continuous bulk trend seems to be justified by the fact that the thinner bed segments are finer-grained and composed of proportionally thinner divisions. The synthetic bulk trend appears to be a concave-upward function that flattens exponentially in the downflow direction. The range-related trend equations allow the pinchout distance of every bed in a turbiditic or tempesitic succession encountered in a well to be predicted and the net spatial pinch-out of a given bed succession to be modelled. However, the trend equations are considered to be tentative, as they require veritication on a wider database. In addition, the statistical analysis revealed occurrence of bed-top undulations in both turbidites and tempestites, which are subtle to gentle and are visually unrecognizable in outcrop sections. Fourier analysis indicates statistically significant, cyclic waveform components in these undulations, with wavelengths of up to 300 m and amplitudes from a few centimetres to 60 cm. The tops of thinner beds have less pronounced and more irregular subtle undulations. The origin of the bed-top undulations is unknown, but there are several wave-like hydrualic phenomena, such as internal waves, to which they may possibly owe their formation. URI: http://hdl.handle.net/10037/1356 File(s) in this item: 2
Janocko_Errata.pdf (126.6Kb)thesis.pdf (26.89Mb) -
Van Eyken, A.P.; Hall, Chris; Svenes, K.R. (Journal article; Peer reviewed, 2000)[+][-]
Abstract: In 1997, reliable operation of the EISCAT Svalbard Radar (ESR) was achieved and a rocket launching facility at Ny Ålesund on Svalbard (79°N, 12°E) (SVALRAK) was established. On 20 November, 1977, the first instrumented payload was launched from SVALRAK. Although the payload configuration had been flown many times previously from Andøya Rocket Range on the Norwegian mainland, this presented an unprecedented in situ determination of positive ion density over Svalbard. Simultaneously, ESR measured similar density profiles but in a higher altitude regime. We have combined the ESR measurements with ionosonde data to establish a calibration and subsequently combined the ground-based and in situ determined profiles to give a composite positive ion density profile from the mesosphere to the thermosphere. URI: http://hdl.handle.net/10037/587 File(s) in this item: 1
article.pdf (484.4Kb) -
Knutsen, Joachim Sveia (Master thesis; Mastergradsoppgave, 02-Jun-2008)[+][-]
Abstract: New to the ESR common programmes is the inclusion of plasma lines along with the standard ion power density spectrum. Using data from the IPY common programme, a programme that has been run all through the International Polar Year, we have gone through large amounts of analysed data trying to find periods in time that fulfils the known criteria for finding Naturally Enhanced Ion Acoustic Lines (NEIALs), i.e. increased electron densities and penetration depth, a high electron temperature (>3000K) that is simultaneously equal to or greater than three times the ion temperature (Te>3Ti) and an increase in ion outflow velocities. Our primary focus has been on the parts of the year where conditions allow simultaneous runs of the Meridian Scanning Photometer (MSP) instrument over Svalbard, i.e. the dark winter months of December, January and February of 2007/2008. We get several results indicating field-aligned currents going both away and towards the radar simultaneously as well as several NEIALs occurring at altitudes that are normally considered to be too low with regards to some of the leading theories on the subject. Where such are observed, NEIALs are presented along with the corresponding plasma lines, as well as MSP plots, magnetometer data and the parameters of the solar wind taken by the ACE satellite to try and find more information regarding NEIALs and the underlying processes that cause them. A brief description of the leading theories regarding NEIALs is also included so we can argue whether or not our observations either strengthens or weakens these theories. URI: http://hdl.handle.net/10037/1766 File(s) in this item: 1
thesis.pdf (4.317Mb) -
Kruglikov, Boris (Chapter; Bokkapittel, 26-Sep-2008)[+][-]
Abstract: In 1896 Tresse gave a complete description of relative differential invariants for the pseudogroup action of point transformations on the 2nd order ODEs. The purpose of this paper is to review, in light of modern geometric approach to PDEs, this classification and also discuss the role of absolute invariants and the equivalence problem. URI: http://hdl.handle.net/10037/2108 File(s) in this item: 1
article.pdf (296.0Kb) -
Hall, Chris; Chshyolkova, Tatyana; Manson, Alan; Meek, Chris; Aso, Takehiko; Avery, S. K.; Hocking, W. K.; Igarashi, K.; Jacobi, C.; Makarov, N.; Mitchell, Nick; Murayama, Y.; Singer, Werner; Thorsen, D.; Tsutsumi, Masaki (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)[+][-]
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