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- Backrud, Marie, et al.
(author)
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Interferometric Identification of Ion Acoustic Broadband Waves in the Auroral Region : CLUSTER Observations
- 2005
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 32:21
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Journal article (peer-reviewed)abstract
- [1] We determine the phase velocity and k vector for parallel and oblique broadband extremely low frequency, ELF, waves on nightside auroral magnetic field lines at altitudes around 4.6 RE. We use internal burst mode data from the EFW electric field and wave instrument onboard the Cluster spacecraft to retrieve phase differences between the four probes of the instrument. The retrieved characteristic phase velocity is of the order of the ion acoustic speed and larger than the thermal velocity of the protons. The typical wavelength obtained from interferometry is around the proton gyro radius and always larger than the Debye length. We find that in regions with essentially no suprathermal electrons above a few tens of eV the observed broadband waves above the proton gyro frequency are consistent with upgoing ion acoustic and oblique ion acoustic waves.
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- Pellinen-Wannberg, Asta, 1953-, et al.
(author)
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The forthcoming EISCAT_3D as an extra-terrestrial matter monitor
- 2016
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In: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 123, s. 33-40
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Journal article (peer-reviewed)abstract
- It is important to monitor the extra-terrestrial dust flux in the Earth’s environment and into the atmosphere. Meteoroids threaten the infrastructure in space as hypervelocity hits by micron-sized granules continuously degrade the solar panels and other satellite surfaces. Through their orbital elements meteoroids can be associated to the interplanetary dust cloud, comets, asteroids or the interstellar space. The ablation products of meteoroids participate in many physical and chemical processes at dierent layers inthe atmosphere, many of them occurring in the polar regions.High-power large-aperture (HPLA) radars, such as the tristatic EISCAT UHF together with the EISCAT VHF, have been versatile instruments for studying many properties of the meteoroid population, even though they were not initially designed for this purpose. The future EISCAT_3D will comprise a phased-array transmitter and several phased-array receivers distributed in Northern Scandinavia. These will work at 233 MHz centre frequency with power up to 10 MW and run advanced signal processing systems. The facility will in many aspects be superior to its predecessors as the first radar to combine volumetric-, aperture synthesis- and multistatic imaging as well as adaptive experiments. The technical design goals of the radar respond to the scientific requests from the user community. The VHF frequency and the volumetric imaging capacity will increase the collecting volume compared to the earlier UHF, the high transmitter power will increase the sensitivity of the radar, and the interferometry will improve the spatial resolution of the orbit estimates. The facility will be able to observe and define orbits to about 10% of the meteors from the established mass flux distribution that are large or fast enough to produce an ionization mantle around the impacting meteoroid within the collecting volume. The estimated annual mean of about 190 000 orbits per day with EISCAT_3D gives many orders of magnitude higher detected orbit rates than the earlier tristatic UHF radar.
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- Tjulin, Anders
(author)
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Using simple-pole distribution functions for calculations in kinetic theory of waves in a plasma
- 1999
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In: Journal of Technical Physics. - : Warszawa; Institute of Fundamental Technological Research. ; , s. 25-28
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Conference paper (peer-reviewed)abstract
- If simple-pole distribution functions are introduced, it is possible to calculate dispersion relations in many plasmas in a rather simple way, using the residue theorem of complex analysis to evaluate integrals. The simple-pole distribution functions are
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