Now showing items 1-10 of 429
A Possible Explanation of Interhemispheric Asymmetry of Equatorial Plasma Bubbles in Airglow Images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-28)
Equatorial plasma bubbles resulting from equatorial spread urn:x-wiley:jgra:media:jgra55597:jgra55597-math-0002 are well known to be aligned along the Earth's geomagnetic fields. During the geomagnetic storm on 17 March 2015, all‐sky airglow observations from Tirunelveli (8.7°N, 77.8°E, 1.7°N dip latitude) showed an apparent interhemispheric asymmetry in the tilt of the equatorial plasma bubbles. ...
Joint optimization of an autoencoder for clustering and embedding
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-21)
Deep embedded clustering has become a dominating approach to unsupervised categorization of objects with deep neural networks. The optimization of the most popular methods alternates between the training of a deep autoencoder and a k-means clustering of the autoencoder’s embedding. The diachronic setting, however, prevents the former to beneft from valuable information acquired by the latter. In ...
Estimating Radiative Forcing With a Nonconstant Feedback Parameter and Linear Response
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-06)
A new algorithm is proposed for estimating time-evolving global forcing in climate models. The method is a further development of the work of Forster et al. (2013), <a href=https://doi.org/10.1002/jgrd.50174>https://doi.org/10.1002/jgrd.50174</a>, taking into account the non-constancy of the global feedbacks. We assume that the non-constancy of this global feedback can be explained as a time-scale ...
Measuring Wind Speed Using the Internal Stabilization System of a Quadrotor Drone
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-16)
This article proposes a method of measuring wind speed using the data logged by the autopilot of a quadrotor drone. Theoretical equations from works on quadrotor control are utilized and supplemented to form the theoretical framework. Static thrust tests provide the necessary parameters for calculating wind estimates. Flight tests were conducted at a test site with laminar wind conditions with the ...
Shearlets as feature extractor for semantic edge detection: The model-based and data-driven realm: Shearlets for Semantic Edge Detection
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-25)
Semantic edge detection has recently gained a lot of attention as an image-processing task, mainly because of its wide range of real-world applications. This is based on the fact that edges in images contain most of the semantic information. Semantic edge detection involves two tasks, namely pure edge detection and edge classification. Those are in fact fundamentally distinct in terms of the level ...
Arctic Field Summer Schools: training and awareness in the Arctic
(Conference object; Konferansebidrag, 2020-01)
A series of three summer schools engaged nearly fifty graduate students in exploring science questions related to current Arctic challenges, and brought together leading Arctic researchers from the partner institutions. Each partner organised a Field School and each had their own unique styles and emphasis. This collaboration aimed to deepen the Arctic knowledge of the young generation, and to create ...
First observations of the McMurdo-South Pole oblique ionospheric HF channel
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-09)
We present the first observations from a new low-cost oblique ionosonde located in Antarctica. The transmitter is located at McMurdo Station, Ross Island, and the receiver at Amundsen–Scott Station, South Pole. The system was demonstrated successfully in March 2019, with the experiment yielding over 30 000 ionospheric echoes over a 2-week period. These data indicate the presence of a stable E layer ...
Electron heating by HF pumping of high-latitude ionospheric F-region plasma near magnetic zenith
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-06)
High-frequency electromagnetic pumping of ionospheric F-region plasma at high and mid latitudes gives the strongest plasma response in magnetic zenith, antiparallel to the geomagnetic field in the Northern Hemisphere. This has been observed in optical emissions from the pumped plasma turbulence, electron temperature enhancements, filamentary magnetic field-aligned plasma density irregularities, and ...
Radar imaging with EISCAT 3D
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-04)
A new incoherent scatter radar called EISCAT 3D is being constructed in northern Scandinavia. It will have the capability to produce volumetric images of ionospheric plasma parameters using aperture synthesis radar imaging. This study uses the current design of EISCAT 3D to explore the theoretical radar imaging performance when imaging electron density in the E region and compares numerical techniques ...
Malin letar oljespill i ishavet
(Chronicle; Kronikk, 2020-03-13)