Blar i forfatter "Rietveld, Michael T."

Viser treff 1-20 av 22

    • The behavior of electron density and temperature during ionospheric heating near the fifth electron gyrofrequency 

      Wu, Jun; Wu, Jian; Rietveld, Michael T.; Häggström, I.; Zhao, Haisheng; Xu, Zhengwen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-27)
      The experimental phenomena involving the changes in electron temperature and electron density as a function of pump frequency during an ionospheric heating campaign at European Incoherent Scatter near Tromsø, Norway, are reported. When the pump frequency is slightly above the fifth electron gyrofrequency, the UHF radar observation shows some apparent enhancements over a wide altitude range in radar ...

    • A case study of a sporadic sodium layer observed by the ALOMAR Weber Na lidar 

      Rietveld, Michael T.; Nesse, H.; Heinrich, D.; Williams, B.; Hoppe, Ulf-Peter; Stadsnes, J.; Singer, W.; Blum, U.; Sandanger, M. I.; Trondsen, E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2008-05-28)
      Several possible mechanisms for the production of sporadic sodium layers have been discussed in the literature, but none of them seem to explain all the accumulated observations. The hypotheses range from direct meteoric input, to energetic electron bombardment on meteoric smoke particles, to ion neutralization, to temperature dependent chemistry. The varied instrumentation located on Andøya ...

    • Comparison of high latitude electron density profiles obtained with the GPS radio occultation technique and EISCAT measurements. 

      Stolle, C.; Rietveld, Michael T.; Jakowski, N.; Schlegel, K: (Journal article; Peer reviewed; Tidsskriftartikkel, 2004)
      To obtain a comprehensive view on high latitude processes by applying different observation techniques, the SIRCUS campaign was initiated in 2001/2002. This paper compares electron density profiles derived from CHAMP radio occultation data and those measured with the EISCAT facility. Since ionospheric profiling with the help of space-based received GPS is a relatively new technique, validations with ...

    • Comparison of the orientation of small-scale electron density irregularities and F region plasma flow direction. 

      Rietveld, Michael T.; Tereshchenko, E.D.; Brekke, Asgeir; Khudukon, B.Z.; Kozlova, M.O.; Evstafiev, O.V.; Nygren, T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2000)
      Results are shown from an experimental campaign where satellite scintillation was observed at three sites at high latitudes and, simultaneously, the F region plasma flow was measured by the nearby EISCAT incoherent scatter radar. The anisotropy parameters of field-aligned irregularities are determined from amplitude scintillation using a method based on the variance of the relative logarithmic ...

    • Conditions for Topside Ion Line Enhancements 

      Rexer, Theresa; Leyser, Thomas; Gustavsson, Björn Johan; Rietveld, Michael T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-17)
      Enhanced ion line spectra as a response to magnetic field-aligned high frequency (HF) pumping of the overdense polar ionosphere with left-handed circular polarization, can be observed at the top and bottomside F-region ionosphere under certain conditions. The European Incoherent Scatter (EISCAT) UHF radar was directed in magnetic zenith on October 18th and 19th, 2017 while stepping the pump ...

    • Controlled beat-wave Brillouin scattering in the ionosphere 

      Eliasson, Bengt; Senior, A.; Rietveld, Michael T.; Phelps, A.D.R.; Cairns, R.A.; Ronald, K.; Speirs, D.C.; Trines, R.M.G.M.; McCrea, Ian; Bamford, R.; Mendonça, J.T.; Bingham, R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-27)
      Stimulated Brillouin scattering experiments in the ionospheric plasma using a single electromagnetic pump wave have previously been observed to generate an electromagnetic sideband wave, emitted by the plasma, together with an ion- acoustic wave. Here we report results of a controlled, pump and probe beat-wave driven Brillouin scattering experiment, in which an ion-acoustic wave generated by the ...

    • Directional features of the downshifted peak observed in HF-induced stimulated electromagnetic emission spectra obtained using an interferometer. 

      Rietveld, Michael T.; Tereshchenko, E.D.; Belyey, Vasyl; Yurik, R.Yu; Brekke, Asgeir; Khudukon, B.Z.; Isham, B.; Hagfors, T.; Grill, M. (Journal article; Peer reviewed; Tidsskriftartikkel, 2006-08-09)
      A high frequency (HF) ionospheric modification experiment was carried out between 25 September and 8 October 2004, using the EISCAT HF transmitter located near Tromsø, Norway. During this experiment the spectra of the stimulated HF sideband waves (stimulated electromagnetic emission or SEE) induced by the HF pump were observed using an interferometer consisting of three spaced receiving antennas ...

    • The electron energy distribution during HF pumping, a picture painted with all colors. 

      Rietveld, Michael T.; Gustavsson, B.; Sergienko, T.; Grydeland, Tom; La Hoz, Cesar; Kosch, M.J.; Brändström, B.U.E.; Leyser, T.B.; Isham, B.; Gallop, P.; Aso, T.; Ejiri, M.; Steen, A.; Kaila, K.; Jussila, J.; Holma, H. (Journal article; Peer reviewed; Tidsskriftartikkel, 2005-07-28)
      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 ...

    • ELF wave generation in the ionosphere using pulse modulated HF heating. Initial tests of a technique for increasing ELF wave generation efficiency. 

      Barr, R.; Rietveld, Michael T.; Stubbe, P. (Journal article; Peer reviewed; Tidsskriftartikkel, 1999)
      This paper describes the results of a preliminary study to determine the effective heating and cooling time constants of ionospheric currents in a simulated modulated HF heating, `beam painting' configuration. It has been found that even and odd harmonics of the fundamental ELF wave used to amplitude modulate the HF heater are sourced from different regions of the ionosphere which support significantly ...

    • GLONASS Observation of Artificial Field-Aligned Plasma Irregularities Near Magnetic Zenith During EISCAT HF Experiment 

      Sato, Hiroatsu; Rietveld, Michael T.; Jakowski, Norbert (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-19)
      We report on simultaneous observation of artificial plasma density irregularities near the magnetic zenith (MZ) by incoherent scatter radar and GNSS satellite in the high latitude. During an EISCAT (European Incoherent Scatter Scientific Association) HF heating experiment, a GLONASS satellite signal intersected the disturbed ionospheric volume along the local magnetic field lines. The satellite ...

    • History of the Tromsø ionosphere heating facility 

      Rietveld, Michael T.; Stubbe, Peter (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-22)
      We present the historical background of the construction of a major ionospheric heating facility, “Heating”, near Tromsø, Norway, in the 1970s by the Max Planck Institute for Aeronomy; we also detail the facility’s subsequent operational history to the present. Heating was built next to the European Incoherent Scatter Scientific Association (EISCAT) incoherent scatter (IS) radar facility and in a ...

    • Infrasound - the cause of strong Polar Mesosphere Winter Echoes? 

      Rietveld, Michael T.; Kirkwood, S.; Chilson, P.; Belova, E.; Häggström, I.; Singer, W.; Dalin, P. (Journal article; Peer reviewed; Tidsskriftartikkel, 2006-03-23)
      The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin layers of strongly enhanced radar echoes from the mesosphere (Polar Mesosphere Winter Echoes - PMWE) during a solar proton event in November 2004. Using the interferometric capabilities of ESRAD it was found that the scatterers responsible for PMWE show very high horizontal travel speeds, up to 500 ms-1 or more, and ...

    • An interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra. 

      Rietveld, Michael T.; Isham, B.; Hagfors, T.; Belyey, Vasyl; La Hoz, Cesar; Khudukon, B.; Brekke, Asgeir; Yurik, R.Yu; Tereshchenko, E.D.; Grill, M.; Heinselman, C. (Journal article; Peer reviewed; Tidsskriftartikkel, 2005-01-31)
      When the Earth's ionosphere is irradiated by a radiofrequency (RF) electromagnetic wave of sufficiently high power density and tuned to match a natural E- or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed ...

    • Irregular structures of the F layer at high latitudes during ionospheric heating. 

      Tereshchenko, E.D.; Rietveld, Michael T.; Brekke, Asgeir; Kozlova, M.O.; Evstafiev, O.V.; Khudukon, B.Z.; Nygren, T. (Journal article; Peer reviewed; Tidsskriftartikkel, 2000)
      Results on heating the ionospheric F region above Tromsø, Norway are presented. The ionosphere was monitored by satellite tomography and amplitude scintillation methods as well as the EISCAT incoherent scatter radar. No effect of heating was observed in the daytime. In the evening and in the pre-midnight sector, noticeable tilts of the F region were observed during heating periods. The tilts overlapped ...

    • Modification of the high-latitude ionospheric F region by high-power HF radio waves at frequencies near the fifth and sixth electron gyroharmonics 

      Borisova, Tatiana D.; Blagoveshchenskaya, Nataly F.; Kalishin, Aleksei S.; Rietveld, Michael T.; Yeoman, Timothy Kenneth; Hägström, I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-01)
      We study the modification effects of the high-latitude ionospheric F region induced by a highpower O-mode HF radio wave injected towards the magnetic zenith, at frequencies near the fifth and sixth electron gyroharmonics using the EISCAT/Heating facility. Multi-instrument diagnostics with the EISCAT incoherent scatter radar (930 MHz) at Tromsø, Norway, the CUTLASS coherent radar at Hankasalmi, ...

    • Modulation of polar mesospheric summer echoes (PMSEs) with high-frequency heating during low solar illumination 

      Gunnarsdottir, Tinna; Mann, Ingrid; Poggenpohl, Arne Hendrik; Mahmoudian, Alireza; Dalin, Peter; Rietveld, Michael T.; Haeggstroem, Ingemar (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-14)
      Polar mesospheric summer echo (PMSE) formation is linked to charged dust/ice particles in the mesosphere. We investigate the modulation of PMSEs with radio waves based on measurements with EISCAT VHF radar and EISCAT heating facility during low solar illumination. The measurements were made in August 2018 and 2020 around 20:02 UT. Heating was operated in cycles with intervals of 48 s on and 168 ...

    • Multi-frequency HF radar measurements of artificial F-region field-aligned irregularities. 

      Senior, A.; Rietveld, Michael T.; Borisov, N.D.; Kosch, M.J.; Yeoman, T.K.; Honary, F. (Journal article; Tidsskriftartikkel; Peer reviewed, 2004-11-03)
      We present radar backscatter power measurements using the CUTLASS HF radar at Hankasalmi, Finland from F-region field-aligned irregularities induced by HF radio pumping with the EISCAT Heating facility. A novel radar operating mode is used in which the radar frequency is rapidly swept through a number of bands, making use of the varying ionospheric refraction to probe different heights within the ...

    • On mechanisms for high-frequency pump-enhanced optical emissions at 557.7 and 630.0gnm from atomic oxygen in the high-latitude F-region ionosphere 

      Leyser, Thomas B.; Sergienko, Tima; Brändström, Urban; Gustavsson, Björn Johan; Rietveld, Michael T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-13)
      The EISCAT (European Incoherent Scatter Scientific Association) Heating facility was used to transmit powerful high-frequency (HF) electromagnetic waves into the Fregion ionosphere to enhance optical emissions at 557.7 and 630.0 nm from atomic oxygen. The emissions were imaged by several stations of ALIS (Auroral Large Imaging System) in northern Sweden, and the EISCAT UHF incoherent scatter radar ...

    • Probing of medium-scale traveling ionospheric disturbances using HF-induced scatter targets 

      Blagoveshchenskaya, N. F.; Rietveld, Michael T.; Borisova, T. D.; Kornienko, V. A.; Moskvin, I. V.; Frolov, V. L.; Uryadov, V. P.; Kagan, L. M.; Yampolski, Yu. M.; Galushko, V. L.; Koloskov, A. V.; Kasheev, S. B.; Zalizovski, A. V.; Vertogradov, G. G.; Vertogradov, V. G.; Kelley, M. C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2006-09-20)
      Experimental results from the Tromsø and Sura heating experiments at high and mid-latitudes are examined. It is shown that the combination of HF-induced target and bi-static HF Doppler radio scatter observations is a profitable method for probing medium-scale traveling ionospheric disturbances (TIDs) at high and mid-latitudes. HF ionospheric modification experiments provide a way of producing ...

    • The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes 

      Rietveld, Michael T.; Tereshcenko, E.D.; Khudukon, B.Z.; Brekke, Asgeir; Isham, B.; Hagfors, T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2006-11-21)
      Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF) transmitter located near Tromsø (Norway). Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers ...