Viser treff 210-229 av 942

    • Dust Trajectory Calculations in the Inner Heliosphere and Circumstellar Debris Disks 

      Mann, Ingrid; Stamm, Johann Immanuel; Czechowski, Andrzej; Baumann, Carsten; Myrvang, Margaretha; Li, Aigen (Conference object; Konferansebidrag, 2018)
    • Dust trajectory simulations around Sun, Vega, and Fomalhaut 

      Stamm, Johann Immanuel; Czechowski, Andrzej; Mann, Ingrid; Baumann, Carsten; Myrvang, Margaretha (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-20)
      <p><i>Context - </i>Vega and Fomalhaut display a thermal emission brightness that can possibly arise from hot dust near the stars, an inner extension of their planetary debris disks. There was brought up an idea that nm-sized dust particles are kept in the vicinity of the stars by electromagnetic forces. This resembles the trapping that model calculations show in the corotating magnetic field in the ...
    • Dynamic rayed aurora and enhanced ion-acoustic radar echoes 

      Blixt, Erik Mårten; Ivchenko, N.; Hagfors, T.; Grydeland, Tom; Trondsen, T.S.; La Hoz, Cesar; Lanchester, B.S.; Løvhaug, Unni Pia (Journal article; Tidsskriftartikkel; Peer reviewed, 2005-01-31)
      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 ...
    • Dynamics of Dust Particles near Sun, Vega and Fomalhaut 

      Stamm, Johann Immanuel; Baumann, Carsten; Czechowski, Andrzej; Mann, Ingrid; Myrvang, Margaretha (Conference object; Konferansebidrag, 2018)
    • Dynamics of nanodust in the vicinity of a stellar corona: Effect of plasma corotation 

      Czechowski, Andrzej; Mann, Ingrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-24)
      Context - In the vicinity of the Sun or other stars, the motion of the coronal and stellar wind plasma must include some amount of corotation, which could affect the dynamics of charged dust particles. In the case of the Sun, this region is now investigated in situ by the Parker Solar Probe. Charged dust particles coming from the vicinity of the Sun can also reach, and possibly be detected by, ...
    • Dynamics of nanodust particles emitted from elongated initial orbits 

      Czechowski, Andrzej; Mann, Ingrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2018)
      <p><i>Context</i>: Because of high charge-to-mass ratio, the nanodust dynamics near the Sun is determined by interplay between the gravity and the electromagnetic forces. Depending on the point where it was created, a nanodust particle can either be trapped in a non-Keplerian orbit, or escape away from the Sun, reaching large velocity. The main source of nanodust is collisional fragmentation of ...
    • Dynamics of the Terra Nova Bay Polynya: The potential of multi-sensor satellite observations 

      Hollands, Thomas; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-10)
      Research on processes leading to formation, maintenance, and disappearance of polynyas in the Polar Regions benefits significantly from the use of different types of remote sensing data. The Sentinels of the European Space Agency (ESA), together with other satellite missions, provide a variety of data from different parts of the electromagnetic spectrum, at different spatial scales, and with ...
    • E-pile model of self-organized criticality 

      Rasmussen, Jens Juul; Milovanov, Alexander V.; Rypdal, Kristoffer (Working paper; Arbeidsnotat, 2007-11-28)
      The concept of percolation is combined with a self-consistent treatment of the interaction between the dynamics on a lattice and the external drive. Such a treatment can provide a mechanism by which the system evolves to criticality without fine tuning, thus offering a route to self-organized criticality (SOC) which in many cases is more natural than the weak random drive combined with ...
    • Eastward-expanding auroral surges observed in the post-midnight sector during a multiple-onset substorm 

      Tanaka, Yoshimasa; Ogawa, Yasunobu; Kadokura, Akira; Partamies, Noora; Whiter, Daniel; Enell, Carl-Fredrik; Brändström, Urban; Sergienko, Tima; Gustavsson, Björn Johan; Kozlovsky, Alexander; Miyaoka, Hiroshi; Yoshikawa, Akimasa (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-09)
      We present three eastward-expanding auroral surge (EEAS) events that were observed intermittently at intervals of about 15 min in the post-midnight sector (01:55–02:40 MLT) by all-sky imagers and magnetometers in northern Europe. It was deduced that each surge occurred just after each onset of a multiple-onset substorm, which was small-scale and did not clearly expand westward, because they were ...
    • Eddy Detection in the Marginal Ice Zone with Sentinel-1 Data Using YOLOv5 

      Khachatrian, Eduard; Sandalyuk, Nikita V.; Lozou, Pigi (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-24)
      The automatic detection and analysis of ocean eddies in the marginal ice zone via remote sensing is a very challenging task but of critical importance for scientific applications and anthropogenic activities. Therefore, as one of the first steps toward the automation of the eddy detection process, we investigated the potential of applying YOLOv5, a deep convolutional neural network architecture, to ...
    • Effect of caffeine and other xanthines on liver sinusoidal endothelial cell ultrastructure 

      Mao, Hong; Szafranska, Karolina; Kruse, Larissa Dorothea; Holte, Christopher Florian; Wolfson, Deanna; Ahluwalia, Balpreet Singh; Whitchurch, Cynthia B.; Cole, Louise; Lockwood, Glen P.; Diekmann, Robin; Le Couteur, David; Cogger, Victoria C.; McCourt, Peter Anthony (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-17)
      Xanthines such as caffeine and theobromine are among the most consumed psychoactive stimulants in the world, either as natural components of cofee, tea and chocolate, or as added ingredients. The present study assessed if xanthines affect liver sinusoidal endothelial cells (LSEC). Cultured primary rat LSEC were challenged with xanthines at concentrations typically obtained from normal consumption of ...
    • Effect of dynamical friction on interchange motion of plasma filaments 

      Kube, Ralph; Garcia, Odd Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
    • The effect of electron bite-outs on artificial electron heating and the PMSE overshoot. 

      Belova, E.; Kassa, M.; Havnes, O. (Journal article; Peer reviewed; Tidsskriftartikkel, 2005-12-23)
      We have considered the effect that a local reduction in the electron density (an electron bite-out), caused by electron absorption on to dust particles, can have on the artificial electron heating in the height region between 80 to 90 km, where noctilucent clouds (NLC) and the radar phenomenon PMSE (Polar Mesospheric Summer Echoes) are observed. With an electron density profile without ...
    • Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines. 

      Guio, Patrick; Lilensten, J. (Journal article; Tidsskriftartikkel, 1999)
      In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geom- etry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage ...
    • The effect of vertical mixing on the horizontal drift of oil spills 

      Röhrs, Johannes; Dagestad, Knut-Frode; Asbjørnsen, Helene; Nordam, Tor; Skancke, Jørgen; Jones, Cathleen; Brekke, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-21)
      Vertical and horizontal transport mechanisms for marine oil spills are investigated using numerical model simulations. To realistically resolve the 3-D development of a spill on the ocean surface and in the water column, recently published parameterizations for the vertical mixing of oil spills are implemented in the open-source trajectory framework OpenDrift (https://doi.org/10.5281/zenodo.1300358, ...
    • Effect of Wind Direction and Incidence Angle on Polarimetric SAR Observations of Slicked and Unslicked Sea Surfaces 

      Skrunes, Stine; Brekke, Camilla; Jones, Cathleen Elaine; Espeseth, Martine; Holt, Benjamin (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-12)
      The objective of this paper is to investigate the dependency of oil spill observations in polarimetric SAR data on imaging geometry, i.e., on incidence angle and look direction relative to the wind. The study is based on quad-polarization data acquired by the Uninhabited Aerial Vehicle Synthetic Aperture Radar over experimental oil slicks under relatively high winds of 10–12 m/s over an 8-hour period. ...
    • Effect on the longitudinal coherence properties of a pseudothermal light source as a function of source size and temporal coherence 

      Ahmad, Azeem; Mahanty, Tanmoy; Dubey, Vishesh; Butola, Ankit; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-01)
      In the present Letter, a synthesized pseudothermal light source having high temporal coherence (TC) and low spatial coherence (SC) properties is used. The longitudinal coherence (LC) properties of the spatially extended monochromatic light source are systematically studied. The pseudothermal light source is generated from two different monochromatic laser sources: He–Ne (at 632 nm) and DPSS (at 532 ...
    • Effects of Ocean Acidification and Warming on Sperm Activity and Early Life Stages of the Mediterranean Mussel (Mytilus galloprovincialis) 

      Vihtakari, Mikko; Hendriks, Iris E.; Holding, Johnna; Renaud, Paul E.; Duarte, Carlos M.; Havenhand, Jon N. (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Larval stages are among those most vulnerable to ocean acidification (OA). Projected atmospheric CO2 levels for the end of this century may lead to negative impacts on communities dominated by calcifying taxa with planktonic life stages. We exposed Mediterranean mussel (Mytilus galloprovincialis) sperm and early life stages to pHT levels of 8.0 (current pH) and 7.6 (2100 level) by manipulating pCO2 ...
    • Effects of particle precipitation on the polar mesospheric summer echoes observed by EISCAT VHF 224 MHz radar 

      Viswanathan, Lakshmi Narayanan; Häggström, Ingemar; Mann, Ingrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-23)
      We present the results from investigation of spectra of polar mesospheric summer echoes (PMSE) observed with EISCAT VHF 224 MHz radar during energetic particle precipitation events in the summer of 2019. We used the sudden enhancements in electron densities derived from the VHF observations above 90 km as indicators of particle precipitation. We find that the altitude extent of the PMSE increased ...
    • Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone 

      Edvardsen, Inge; Johnsen, Magnar Gullikstad; Løvhaug, Unni Pia (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-02)
      The geomagnetic field often experiences large fluctuations, especially at high latitudes in the auroral zones. We have found, using simulations, that there are significant differences in the substorm signature, in certain coordinate systems, as a function of longitude. This is confirmed by the analysis of real, measured data from comparable locations. Large geomagnetic fluctuations pose ...