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Stellar CCD Photometry in the Auroral Zone
(Master thesis; Mastergradsoppgave, 2000-12)Observing pulsating stars in the auroral zone, seemed for many years to be an impossible task. Due to the aurora, the sky is bright and rapidly changing. Precise photometry could only be performed on stars down to 7 th. magnitude.<p> <p>A new instrument for continuous photometry, with the use of CCD technology, and windowed readout, is developed by the Astrophysics group at the University of ... -
An Investigation of Turbulence and Intermittency in the High-Latitude Ionosphere: A Multi Case Study
(Master thesis; Mastergradsoppgave, 2024-06-03)High-latitude electron density irregularities can affect technology such as the Global Navigation Satellite Services (GNSS) by degrading radio signals. These irregularities are not fully understood. In this work we investigate turbulence and intermittency in varying regions of the high- latitude ionosphere using the structure function, empirical flatness and probability density function. Our ... -
Seasonal and interannual variability in hydrography and currents along the Nansen Legacy transect across the Barents Sea
(Master thesis; Mastergradsoppgave, 2023-12-20)The Barents Sea is an Arctic shelf sea that is an important site forwater mass formation and transformation. It is characterized by interactions between Atlanticand Arctic-originWaters, and by strong seasonality in terms of alternating atmospheric and sea-ice conditions throughout the year. How these aspects impact the seasonal evolution of the water column properties is yet to be fully ... -
Leveraging tensor kernels to reduce objective function mismatch in deep clustering
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-29)Objective Function Mismatch (OFM) occurs when the optimization of one objective has a negative impact on the optimization of another objective. In this work we study OFM in deep clustering, and find that the popular autoencoder-based approach to deep clustering can lead to both reduced clustering performance, and a significant amount of OFM between the reconstruction and clustering objectives. To ... -
Extent, duration and timing of the sea ice cover in Hornsund, Svalbard in 2014–2023
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-02-27)The Sentinel-1A/B synthetic aperture radar (SAR) imagery archive between 14 October 2014 and 29 June 2023 was used in combination with a segmentation algorithm to create a series of binary ice/open-water maps of Hornsund fjord, Svalbard, at 50 m resolution for nine seasons (2014/15 to 2022/23). The near-daily (1.57 d mean temporal resolution) maps were used to calculate sea ice coverage for the ... -
Offshore Wind Prediction with Graph Neural Networks
(Mastergradsoppgave; Master thesis, 2024-06-14)Offshore wind energy, especially in regions like the Norwegian Arctic, is a promising source of renewable energy. Graph Neural Networks (GNNs) have shown potential in modeling complex systems like weather, making them suitable for improving wind resource assessments. This thesis investigates the use of GNNs for predicting offshore wind patterns, utilizing high-resolution Synthetic Aperture Radar ... -
Recent Changes in Mid-latitude Wave Propagation
(Mastergradsoppgave; Master thesis, 2024-06-12)In recent years climate change in the polar areas has attracted a lot of attention. Not only for its consequences in polar areas, but also for its possible effects on lower latitudes. A reduced temperature gradient between the polar areas is expected to weaken the mid-latitude jet stream. This weaker jet stream is hypothesised to lead to a reduction in the propagation velocity of atmospheric Rossby ... -
Wind resource assessment using LiDAR
(Mastergradsoppgave; Master thesis, 2024-06-07)This thesis presents a comprehensive wind resource assessment for the expansion of the Fakken wind park in Norway, leveraging Light Detection and Ranging (LiDAR) technology. The measurement campaign conducted from December 2022 to June 2023, aims to detail LiDAR measurement methodologies, analyze collected data, and estimate wind energy production. -
Dual Radar Detections of Meteors Using Calibrated EISCAT UHF Data
(Mastergradsoppgave; Master thesis, 2024-06-03)The atmosphere of Earth experiences a continuous entry of particles of various sizes originating from several sources. Meteoroids, which are called meteors when entering the atmosphere, are particles that can be measured by radars through scattering off the meteor head plasma which forms around the meteor. These measurements can give information on the processes the meteor undergoes as it travels ... -
Investigation into the photon interaction of small mesospheric dust and its impact on the ionospheric charge balance
(Mastergradsoppgave; Master thesis, 2024-05-31)This thesis investigates the charging mechanisms of nano-sized meteoric smoke particles (MSP) in the mesosphere, with a particular focus on the photoionization and photodetachment processes on MSP assuming different materials. The study begins with three theoretical chapters that lay the ground- work for understanding relevant topics like the atmospheric region in question, MSP, the solar ... -
Pulsating Aurora: Optical observations and modelling of the time-variation of ionospheric response to precipitation of pitch-angle-scattered electrons from the magnetosphere
(Mastergradsoppgave; Master thesis, 2024-01-29)This thesis explores the mechanisms governing pulsating auroras by combining observational analysis with theoretical simulations using the AURORA model. The AURORA model simulates electron transport and ionospheric responses, playing a key role in replicating the abrupt onset precipitation of electrons from source altitudes at 3RE, 4.4RE, 6.1RE, and 7.6RE. Eight events of pulsating aurora were ... -
The Role of Clouds in Arctic Climate
(Mastergradsoppgave; Master thesis, 2024-05-14)Anthropogenic climate change is causing the Arctic to warm faster than any other region on Earth, a phenomenon also known as Arctic amplification. The warming and its consequences induce, amongst other things, a change in clouds, impacting their role in the Arctic climate by introducing a feedback. Clouds play an important role in the global radiation budget. They cool the surface by reflecting ... -
Towards seamless environmental prediction–development of Pan-Eurasian EXperiment (PEEX) modelling platform
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-09)The Pan-Eurasian Experiment Modelling Platform (PEEX-MP) is one of the key blocks of the PEEX Research Programme. The PEEX MP has more than 30 models and is directed towards seamless environmental prediction. The main focus area is the Arctic-boreal regions and China. The models used in PEEX-MP cover several main components of the Earth’s system, such as the atmosphere, hydrosphere, pedosphere and ... -
The basics of optical alignment
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-26)Precise optical alignment is critical for high-quality microscopy imaging, especially in custom-built systems. This guide details essential alignment steps, from beam path setup to lens collimation and centering, introduces key tools like pinholes and shearing interferometers, and advocates for a modular construction approach. This article aims to empower microscopy enthusiasts with practical alignment ... -
Impact ionization double peaks analyzed in high temporal resolution on Solar Orbiter
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-05-29)Solar Orbiter is equipped with electrical antennas performing fast measurements of the surrounding electric field. The antennas register high-velocity dust impacts through the electrical signatures of impact ionization. Although the basic principle of the detection has been known for decades, the understanding of the underlying process is not complete, due to the unique mechanical and electrical ... -
Kelvin-Helmholtz versus Gradient drift instability: which one "wins" in the high latitude ionosphere?
(Mastergradsoppgave; Master thesis, 2024-01-14)The high latitude ionosphere is highly irregular, which is caused by plasma patches, flow shears and electron precipitation. These causes are not well understood, but it is thought to be three sources to these irregularities: density gradients, arcs/flow channels and electron precipitation. It is speculated that there are two main mechanisms for the formation of these irregularities. These mechanisms ... -
Cross-population evaluation of cervical cancer risk prediction algorithms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-24)Background - Cervical cancer is a preventable disease, despite being one of the most common types of female cancers worldwide. Integrating existing programs for cervical cancer screening with personalized risk prediction algorithms can improve population-level cancer prevention by enabling more targeted screening and contrive preventive healthcare innovations. While algorithms developed for cervical ... -
Analysis of time series of polarimetric sea ice signatures observed in fast ice it the Belgica Bank area
(Journal article; Tidsskriftartikkel, 2023-10-20)The CIRFA-Cruise 2022 with <i>RV Kronprins Haakon</i> to the north-eastern coast of Greenland in the period April 22nd to May 9th 2022 was organised to perform measurements and make observations which allow for validation of sea ice remote sensing information and forecast products resulting from work in the Centre for Integrated Remote Sensing and Forecasting for Arctic Operations(CIRFA), a Centre ... -
Distinguishing Mineral Oil Slicks from Low Wind Areas using Rapid Repeat Synthetic Aperture Radar Imagery
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-18)A method for differentiating marine oil slicks from radar-dark, low wind areas in open water using rapid repeat SAR imagery is reported. The study uses data acquired by the airborne UAVSAR L-band SAR instrument, imaging the Coal Oil Point seep field near Santa Barbara, California. Time-series of images from three different days are analyzed, all containing both verified oil slicks and low wind zones. ... -
Correlation between Wettability and Dissolution of Calcite in Ion-Free Water
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-13)Calcite, a prevalent mineral in the earth’s crust, plays a pivotal role in various geological and industrial processes, including carbon sequestration, water treatment, and enhanced oil recovery. Understanding how wettability (a crucial surface property influenced by the interaction between calcite and surrounding fluids) affects calcite’s dissolution is essential for optimizing these processes. We ...
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