Measurements of naturally enhanced ion acoustic line (NEIAL) echoes obtained with a five-antenna interferometric imaging radar system are presented. The observations were conducted with the European Incoherent SCATter (EISCAT) radar on Svalbard and the EISCAT Aperture Synthesis Imaging receivers (EASI) installed at the radar site. Four baselines of the interferometer are used in the analysis. Based ...

The generation mechanism for naturally enhanced ion-acoustic echoes is still debated. One important issue is how these enhancements are related to auroral activity. All events of enhanced ion-acoustic echoes observed simultaneously with the EISCAT Svalbard Radar (ESR) and with high-resolution narrow field-of-view auroral imagers have been collected and studied. Characteristic of all the ...

The shape of the electron energy distribution has long been a central question in the field of highfrequency radio-induced optical emission experiments. This report presents estimates of the electron energy distribution function, fe(E), from 0 to 60 eV, based on optical multiwavelength (6300, 5577, 8446, 4278 A° ) data and 930-MHz incoherent scatter radar measurements of ion temperature, electron ...

We present first incoherent scatter radar observations of systematically recurring, high‐frequency (HF)‐enhanced ion line spectra at the topside F‐region ionosphere, during magnetic field aligned HF pumping in an O‐mode polarization. The European Incoherent Scatter UHF radar was directed in magnetic zenith on 9–11 March 2016 while stepping the pump frequency across the double resonance of the fourth ...

We know that the visible Aurora Borealis is structured on many different scales, down to a few tens of metres. By using the EISCAT radars on Svalbard as an interferometer, we have found structures in the radio echoes from the auroral ionosphere on a scale approaching that of the visible aurora, and simultaneously with it, but at far greater ranges. In this thesis we discuss how these radar observations ...

Interferometry applications (e.g., radio astronomy) often wish to optimize the placement of the interferometric elements. One such optimal criterion is a uniform distribution of non-redundant element spacings (in both distance and position angle). While large systems, with many elements, can rely on saturating the sample space, and disregard “wasted” sampling, small arrays with only a few elements ...

In the Arctic, presence of sea ice presents a challenge to safe and sustainable operations. To optimize planning and minimize impact of inadvertent oil spills, oil-in-ice experiments were performed at the HSVA Arctic Environmental Test Basin (AETB) from 14 March to 4 April 2017. Following an under-ice spill and simulated springtime warming, the microscopic movement and distribution of oil in the sea ...

The thesis describes observations of strongly enhanced incoherent scatter plasma lines in the auroral ionosphere which were made with the EISCAT UHF radar in 1985. The linear theory of plasma instabilities is reviewed, and several possible explanations are discussed. The observations were found to be of insufficient resolution to unambiguously resolve which one would be the correct explanation. ...

The real and imaginary parts of baseband signals are obtained from a real narrow–band signal by quadrature mixing, i.e. by mixing with cosine and sine signals at the narrow band’s selected center frequency. We address the consequences of a delay between the outputs of the quadrature mixer, which arise when digital samples of the quadrature baseband signals are not synchronised, i.e. when ...

Arbeidet analyserer tilgjengelig søk og redningskapasitet (SAR), med fokus på søk, med sikte på å avdekke forbedringspunkter. Arbeidet er begrenset til Norges ansvarsområde i henhold til Arktisk råds avtale om søk og redning i Arktis. Redningshelikopter på SAR beredskap består av 2 AS332L1 AWSAR på Svalbard, et Sea King på Banak og et i Bodø. I tillegg har Bristow et EC225 AWSAR helikopter i Hammerfest. ...