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Heavy Molecular and Metallic Ions in the Magnetosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-11-04)Observations and present knowledge of heavy ions with mass ≥ 27 in the magnetosphere are reviewed. There are four ultimate sources of these heavy ions: the solar wind (mainly high charge-state atomic ions), the ionosphere (mainly molecular ions), the atmospheric metal layers that originate ultimately from ablation of meteoroids and possibly space debris (low charge-state metallic ions and metal-rich ... -
The Growth and Decay of Intense GNSS Amplitude and Phase Scintillation During Non‐Storm Conditions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-11-30)A multi‐instrument study is conducted at the dayside polar ionosphere to investigate the spatio‐ temporal evolution of scintillation in Global Navigation Satellite System (GNSS) signals during non‐storm conditions. Bursts of intense amplitude and phase scintillation started to occur at ∼9 MLT and persisted for more than 1 hour implying the simultaneous existence of Fresnel and large‐scale sized ... -
Leveraging Network Science for the Exploration of Deep Learning Latent Representations
(Mastergradsoppgave; Master thesis, 2023-12-15)Deep Neural networks has pushed the boundary for what is achievable in the field of machine learning. At its core the Neural network maps data from an input space, to a highly abstract latent space. The representations of these latent mappings are critical for the neural networks ability to perform the task it is given. However critical, our knowledge on these abstract representations in the latent ... -
Impact of varying solar angles on Arctic iceberg area retrieval from Sentinel-2 near-infrared data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-11-18)Icebergs are part of the glacial mass balance and they interact with the ocean and with sea ice. Optical satellite remote sensing is often used to retrieve the above-waterline area of icebergs. However, varying solar angles introduce an error to the iceberg area retrieval that had not been quantified. Herein, we approximate the iceberg area error for top-of-atmosphere Sentinel-2 near-infrared data ... -
Baffin Bay Ice Export and Production From Sentinel-1, the RADARSAT Constellation Mission, and CryoSat-2: 2016–2022
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-11-13)Baffin Bay is located between Greenland and several islands of the Canadian Arctic, providing a conduit for the downstream transport of ice and freshwater to the North Atlantic via Davis Strait. Using satellite observations from Sentinel‐1, the RADARSAT Constellation Mission, and CryoSat‐2, we estimated the sea ice export through Davis Strait and winter ice production in Baffin Bay from 2016 to ... -
fair-calibrate v1.4.1: calibration, constraining, and validation of the FaIR simple climate model for reliable future climate projections
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-12-03)Simple climate models (also known as emulators) have re-emerged as critical tools for the analysis of climate policy. Emulators are efficient and highly parameterised, where the parameters are tunable to produce a diversity of global mean surface temperature (GMST) response pathways to a given emission scenario. Only a small fraction of possible parameter combinations will produce historically ... -
Studentaktiv læring med store studentgrupper: flervalgsoppgaver i sentrum
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-02-16)To viktige prinsipper for å øke studentenes læring i undervisning er aktiv deltagelse og formativ vurdering. Innføring av disse prinsippene i undervisning med store studentgrupper kan imidlertid by på utfordringer, særlig i nettbasert undervisning. En mulig løsning kan være bruk av flervalgsoppgaver som diagnostisk testing med innsamling av svarene og påfølgende formativ vurdering – en undervisningsform ... -
Bringing it all together: Science priorities for improved understanding of Earth system change and to support international climate policy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-18)We review how the international modelling community, encompassing integrated assessment models, global and regional Earth system and climate models, and impact models, has worked together over the past few decades to advance understanding of Earth system change and its impacts on society and the environment and thereby support international climate policy. We go on to recommend a number of priority ... -
Sea ice mass balance during the MOSAiC drift experiment: Results from manual ice and snow thickness gauges
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-07-09)Precise measurements of Arctic sea ice mass balance are necessary to understand the rapidly changing sea ice cover and its representation in climate models. During the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, we made repeat point measurements of snow and ice thickness on primarily level first- and second-year ice (FYI, SYI) using ablation stakes and ... -
Point-cloud clustering and tracking algorithm for radar interferometry
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-22)In data mining, density-based clustering, which entails classifying datapoints according to their distributions in some space, is an essential method to extract information from large datasets. With the advent of software-based radio, ionospheric radars are capable of producing unprecedentedly large datasets of plasma turbulence backscatter observations, and new automatic techniques are needed to ... -
Polar mesospheric summer echo (PMSE) multilayer properties during the solar maximum and solar minimum
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-11-11)Polar mesospheric summer echoes (PMSEs) are radar echoes that are measured in the upper atmosphere during the summer months and that can occur in several layers. In this study, we aimed to investigate the relationship between PMSE layers ranging from 80 to 90 km altitude and the solar cycle. We investigated 230 h of observations from the EISCAT very high frequency (VHF) radar located near Tromsø, ... -
Deriving the Ionospheric Electric Field From the Bulk Motion of Radar Aurora in the E-Region
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-28)In the auroral E‐region strong electric fields can create an environment characterized by fast plasma drifts. These fields lead to strong Hall currents which trigger small‐scale plasma instabilities that evolve into turbulence. Radio waves transmitted by radars are scattered off of this turbulence, giving rise to the ‘radar aurora’. However, the Doppler shift from the scattered signal does not ... -
Co-located OLCI optical imagery and SAR altimetry from Sentinel-3 for enhanced Arctic spring sea ice surface classification
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-07-10)The Sentinel-3A and Sentinel-3B satellites, launched in February 2016 and April 2018 respectively, build on the legacy of CryoSat-2 by providing high-resolution Ku-band radar altimetry data over the polar regions up to 81° North. The combination of synthetic aperture radar (SAR) mode altimetry (SRAL instrument) from Sentinel-3A and Sentinel-3B, and the Ocean and Land Colour Instrument (OLCI) imaging ... -
Cross-modality sub-image retrieval using contrastive multimodal image representations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-08-13)In tissue characterization and cancer diagnostics, multimodal imaging has emerged as a powerful technique. Thanks to computational advances, large datasets can be exploited to discover patterns in pathologies and improve diagnosis. However, this requires efficient and scalable image retrieval methods. Cross-modality image retrieval is particularly challenging, since images of similar (or even the ... -
Overview of the First Pathloss Radio Map Prediction Challenge
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-06-26)Pathloss quantifies the reduction in power density of a signal radiated from a transmitter. The attenuation is due to large-scale effects such as free-space propagation loss and interactions (e.g., penetration, reflection, and diffraction) of the signal with objects such as buildings, vehicles, trees, and pedestrians in the propagation environment. Many current or planned wireless communications ... -
Automated Sentinel-1 ice type mapping and in-situ validation during the CIRFA-22 cruise
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-05-13)We present a fully-automated workflow to map sea ice types from Sentinel-1 data and transfer the results in near real-time to the research vessel Kronprins Haakon (KPH) in order to support tactical navigation and decision-making during a research cruise conducted towards Belgica Bank in April and May 2022. We used overlapping SAR and optical imagery to train a pixel-wise classifier for the required ... -
A three-point velocity estimation method for two-dimensional coarse-grained imaging data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-09-04)Time delay and velocity estimation methods have been widely studied subjects in the context of signal processing, with applications in many different fields of physics. The velocity of waves or coherent fluctuation structures is commonly estimated as the distance between two measurement points divided by the time lag that maximizes the cross correlation function between the measured signals, but ... -
Waves and Instabilities in Saturn's Magnetosheath: 1 Mirror Mode Waves and Their Impact on Magnetopause Reconnection
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-03) -
Waves and Instabilities in Saturn’s magnetosheath: 2 Dispersion relation analysis
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-03) -
Multi-Instrument and SAMI3-TIDAS Data Assimilation Analysis of Three-Dimensional Ionospheric Electron Density Variations During the April 2024 Total Solar Eclipse
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-08-31)This paper conducts a multi-instrument and data assimilation analysis of the three-dimensional ionospheric electron density responses to the total solar eclipse on 08 April 2024. The altitude-resolved electron density variations over the continental US and adjacent regions are analyzed using the Millstone Hill incoherent scatter radar data, ionosonde observations, Swarm in situ measurements, and a ...
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