A study is undertaken into parameters of the polar auroral and geomagnetic pulsations in the frequency range 1– 4 mHz (Pc5/Pi3) during quiet geomagnetic intervals preceding auroral substorms and non-substorm background variations. Special attention is paid to substorms that occur under parameters of the interplanetary magnetic field (IMF) conditions typical for undisturbed days (“non-triggered ...

Retrievals of sea ice drift from synthetic aperture radar (SAR) images at high spatial resolution are valuable for understanding kinematic behavior and deformation processes of the ice at different spatial scales. Ice deformation causes temporal changes in patterns observed in sequences of SAR images; which makes it difficult to retrieve ice displacement with algorithms based on correlation and ...

This paper shows initial results from estimating Doppler radial surface velocities (RVLs) over Arctic sea ice using the Sentinel-1A (S1A) satellite. Our study presents the first quantitative comparison between ice drift derived from the Doppler shifts and drift derived using time-series methods over comparable time scales. We compare the Doppler-derived ice velocities with global positioning system ...

Equivalent Number of Looks (ENL) is an important parameter in statistical modelling of multi-look Polarimetric SAR (PolSAR) data. In some automated applications of PolSAR images, it is necessary to estimate the ENL in an unsupervised way without any manual intervention. The existing unsupervised estimation of ENL can not obtain accurate estimates for the images with high heterogeneity. To address ...

A resonance probe for measuring the dielectric properties of snow in terms of the resonance frequency is described and tested. The dielectric properties of snow are closely related to the density and the water content in snow. Having a probe capable of measuring the dielectric properties is therefore a useful tool for anyone working with quantitative descriptions of snow properties. In situ measurements ...

In the inductively coupled plasma of the Njord helicon device we have, for the same parameters as for which an ion beam exists, measured a downstream population of high-energy electrons emerging from the source. Separated measurements of energetic tail electrons was carried out by Retarding Field Energy Analyzer (RFEA) with a grounded entrance grid, operated in an electron collection mode. In a ...

A recurrent neural network (RNN) is a universal approximator of dynamical systems, whose performance often depends on sensitive hyperparameters. Tuning them properly may be difficult and, typically, based on a trial-and-error approach. In this work, we adopt a graph-based framework to interpret and characterize internal dynamics of a class of RNNs called echo state networks (ESNs). We design principled ...

In this study we present a method to estimate neutral thermospheric densities using ISR-observations following a sequence of high-frequency radio wave ionospheric heating modi cations in the vicinity of the ionosphere peak density altitude (hmF2), and the results from two different days of observations with low geomagnetic activity levels (AP<4) that are compared to the MSIS model. Slight ...

Optical tree delineation algorithms have previously been used for satellite data. In this thesis, they are adapted for use from an Unmanned Aerial Vehicle (UAV). An evaluation of three algorithms (Valley Following, Region Growing and Marker Controlled Watershed) as well as different pre-filtering was done to find the best algorithm and filter combination for a species independent delineation. The ...