Prosjekt- og MSc-oppgåver - Rom

Interesserte studentar må ta kontakt med personen som er oppførd som rettleiar for å diskutera oppgåva.

Frist for val av oppgåve med start hausten 2008: 15. juni 2008

Ønskje om prosjektoppgåve må sendast til rettleiar innan fristen.

Kontaktperson: Geir.antonsen@matnat.uit.no


Imaging of the nightside proton aurora:

Supervisor: Torsten Aslaksen

The visual aurora is the signature of electric currents that couple the ionosphere with the magnetosphere. The charge carriers are mostly electrons and protons. However, most of the visual emissions is due to electron precipitation. The proton aurora is much harder to detect,
but is nevertheless important to observe in order to get a complete picture of the current systems associated with the aurora. Observations of the proton aurora require very high sensitive video imagers set up together with other video imagers for electron aurora
to discriminate between electron and proton aurora. Image processing will also be required to extract the weak proton aurora.


Processing of TACO data:

Supervisor: Torsten Aslaksen

The TACO platform generates a huge amount of data on the aurora. Questions like aurora arc alignment as a function of solar angle and seasonal variations and statistical occurences of diffuse and pulsating aurora are typical questions that could find their answers in the TACO dataset.


Current free double layers in Njord

Supervisor: Åshild Fredriksen

This is an experimental master project at Aurolab
Double layers in plasmas are nonlinear potential structures which can accelerate plasma particles to large velocities. Such double layers are known from satellite data to exist in the high-altitude ionosphere and they have been proposed to be a source of currents parallel to the magnetic field. In the plasma device Njord they are known to form spontaneously under certain conditions. This is the same type of double layers which is presently being investigated at Australian National University as a source of thrust in a new type of plasma thruster. This project will focus on mapping its geometry and spatial behavior in Njord, and the formation of ion beams emanating from the double layer under various conditions.


Lysende sjikt rundt positivt ladete elektroder i plasma.

Veileder: Åshild Fredriksen

Dette er en eksperimentell masteroppgave ved Aurolab
I laboratorium dannes plasma ved å varme opp en gass ved lavt trykk slik at elektroner rives løs fra atomer eller molekyler i bakgrunnsgassen og danner et plasma med en ioniseringsgrad (antall ioner i forhold til nøytrale) på 1-10%.
Dersom en i et slikt plasma forspenner en skive eller kule av passende størrelse med en tilstrekkelig stor positiv spenning, vil elektroner som akselereres inn mot skiva, delvis ioniseres og delvis eksitere nøytralgassen rundt elektroden, slik at det oppstår et lysende sjikt rundt elektroden. Oppgaven består i å undersøke formasjon av såkalte ’fire balls’ , eller lysende sjikt, rundt en positivt ladet elektrode i et plasma med magnetfelt.

Fig.1

En ‘ildkule’ med en magnet plassert i nærheten (til venstre, utenfor bildet)observert i et eksperiment i Innsbruck oktober 2007.



En gruppe i Innsbruck ledet av Prof. Roman Schrittwieser, har studert denne typen fenomen i umagnetiserte plasma i en tiårs-periode, men bare begrensede studier er hittil gjort på ’fire balls’ i magnetiserte plasma. Ved Aurolab finnes to plasmamaskiner, begge med magnetiserte plasma, og vi har dermed spesielle forutsetninger for å studere fenomenet under slike betingelser. Vi har også en studentutvekslings-avtale med Universitetet i Innsbruck, slik at studenter på dette prosjektet vil ha anledning til å dra dit på lengre eller kortere opphold for å lære mer om denne typen fenomener.
Prosjektet vil kunne deles inn i et prosjekt på 10 + 30 studiepoeng, der et mindre prosjekt på høsten vil gi studenten innføring i å operere plasmamaskinen, danne ’fire balls’ og inspisere dem visuelt, samt bli kjent med litteraturen på området.
Master-oppgaven i vårsemesteret vil fokusere på å undersøke ved hjelp av elektrostatiske prober hvordan fenomenet avhenger av endringer i plasmaparametre, som for eksempel gasstrykk og magnetfelt. Potensial-profiler foran elektroden vil være av spesiell interesse.


Radar Imaging: Optimum location of a 6th antenna for the EISCAT Svalbard Radar (ESR)

Supervisor: Cæsar La Hoz

Radar imaging is an active imaging technique that employs a radar to illuminate a scattering medium (like a camera flash). The scattered signals are collected back by a set of carefully spaced antennas (like a camera lens, as if it were). The outputs of the antenna receivers are processed properly (like the camera CCD+processor) to construct an image of the scattering medium. This constitutes an active synthetic imaging array with its own illuminator. The ESR has presently 5 antennas, the two large ones (32 and 42 m in diameter) that can be employed to illuminate the atmosphere/ionosphere, and to receive as well, and 3 small antennas only for reception. This constitutes a 5-antenna imaging interferometer with 10 baselines (5x(5-1)/2=10 different pairs of antennas). The positions of the antennas are carefully computed in order to optimize the filling of a space created by the geometrical arrangement resulting from all different pairs of antennas, called baselines. A particular function defined in this space, namely the cross-correlations between the signals stemming from all baselines is called the Visibility Function. The image of the scattering medium (called the Brightness Distribution) is obtained by a 2-dimensional Fourier transform of the visibility function (ideally; in practice this produces sub-optimum results; there are better inversion algorithms). This project is aimed at finding the optimum position of a 6th antenna to the ESR. The student will first get acquainted with the basic principles of interferometric imaging. Then alternatives of optimum localizations of the 6th antenna will be calculated. The main criterion is that the baseline space --- the sapace where the visibility function is defined --- shall be maximally covered by the available number of baselines, in this case 6x(6-1)/2=30 baseline points. The ideal distribution of baseline points is a 2-dimensional evenly spaced grid, which is not attainable in practice.


The Doppler shift of Plasma Lines in Radar Incoherent Scattering

Supervisor: Cæsar La Hoz

The spectrum of Radar Incoherent Scattering (the technique used by EISCAT to investigate the ionosphere) has two spectral lines, one at low frequency due to ion dynamics called the ion line and another at high frequency due to electron dynamics called the plasma line. These are waves created spontaneously in all plasmas due to intrinsic thermal fluctuations. In a homogeneous, isotropic and stationary plasma (all the velocity distributions will be Maxwellian) these waves are likewise and random. The plasma line then shows an upshifted line with positive Doppler due to waves propagating towards the radar and a downshifted line with negative Doppler due to waves traveling away from the radar. If the plasma does not have a bulk or drift motion, i.e. is not moving as a whole, the two plasma line center frequencies will be symmetric with respect to zero frequency. If the plasma has a drift, the two plasma lines will shift together up or down in frequency depending on the direction of the plasma motion with respect to the radar line of sight. This can be ascertained from a measurement of the plasma line spectrum by calculating the difference of the plasma line center frequencies. However, due to inhomogeneity of the ionospheric plasma, the plasma line center frequencies are not symmetric because the temperature gradient modifies the plasma center frequency in the same way as a Doppler shift does. In order to measure the Doppler shift, it is necessary to know the contribution to the asymmetry by the heat flow (in the plasma kinetic equations the temperature gradient manifests as heat flow). This project is divided into two steps. First, a literature search will reveal previous EISCAT experiments that produced the spectra of both plasma lines. Second, once a set of suitable measurements have been identified and the data acquired, the Doppler shifts of both, the plasma lines and the ion lines, will be calculated. The theory of inhomogeneous plasma is not well developed; the contribution of heat flow to the center plasma frequency is not well understood, principally owing to the difficulty in modeling the velocity distributions of the non-homogeneous ionosphere. For these reasons, and at this stage, only a tentative assessment will be done regarding the contribution of heat flow to the plasma line center frequency. This type of study has a very interesting and useful application, namely that it allows the measurement of field aligned currents from the ground, if the heat flow term is dealt with satisfactorily, that is. Only satellites with in-situ instruments are able to do this kind of measurement. Field aligned currents occur at high latitudes and are associated with auroral phenomena.


Statistics of plasma temperature in the ionosphere using the EISCAT database

Supervisor: Cæsar La Hoz

The EISCAT radars in the mainland (Tromsø, Kiruna, Sodankylä) have been in operation two solar cycles, and the Svalbard radar one solar cycle. Thus, it becomes now possible to make statistical studies of the behaviour of the ionosphere above Scandinavia and above Svalbard over solar cycle scales. The entire EISCAT database has been recently transformed to a suitable and accessible format with accompanying tools by Vasyl Belyey. In this project a study of the statistical properties of the electron and ion temperature will be carried out by calculating histograms with different binnings under different conditions, e.g. seasonal, yearly, daily, geomagnetic, etc., conditions. An assessment will be done regarding the trends revealed by the histograms or other suitable statistical functions/parameters. The tools provided are written in the Python programming language. However, as the format is uniform and independent of the type of experiment or original format of the data, other access tools could be created in other programming languages.