Christer van der - PowerPoint Presentation

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Christer van der Meeren1, Kjellmar Oksavik1,2, Dag Lorentzen2,3, Jøran Moen4,2, Vincenzo Romano51 Birkeland Centre for Space Science, Department of Physics and Technology, University of Bergen, Norway.2 University Centre in Svalbard, Longyearbyen, Norway.2 Birkeland Centre for Space Science, University Centre in Svalbard, Longyearbyen, Norway.4 Department of Physics, University of Oslo, Norway5 Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy

GPS scintillation and irregularities at the front of a tongue of ionization in the

nightside

polar ionosphere over SvalbardSlide2

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionMotivationScintillations in polar cap well correlated with patch activityWhat about continuous TOIs?[Gondarenko and Guzdar, 2004]Slide3

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionBackgroundPlasma irregularities of scale sizes 10m–1km cause scintillations on GPS signalsAmplitude scintillations: 10–100m-scale irregularities, S4 indexPhase scintillations: 100m–1km-scale irregularities, usually σϕ indexSlide4

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionMethodologyCase study of scintillation on the leading edge of a TOI over Svalbardon 31 Oct 20113 GPS receivers (NovAtel GSV4004B GISTM) (2 in NYA, 1 in LYR)EISCAT Svalbard Radar630.0nm ASI at NYASuperDARN Hankasalmi radarSlide5

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionTOI across polar capSlide6

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionTOI across polar capSlide7

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionTOI airglow over SvalbardSlide8

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionGeomagnetic overviewSlide9

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionGPS IPP locationsSlide10

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionGPS parametersSlide11

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionDiscussion – the problems of σϕ[Forte and Radicella, 2002; Béniguel et al., 2004;Forte, 2005; Beach, 2006; Mushini et al., 2012]Phase scintillation does not necessarilyimply irregularitiesMay instead be «false» scintillationsfrom the gradient itselfPoor data detrendingσϕ index sensitive to low-frequency phase variationsGradient = low-frequency phase variation0.1 Hz too low at high latitudes (gradientscorrespond to phase variations > 0.1 Hz)No scintillation after the gradientGradient drift instability (GDI) stable on leading edgesIrregularities would most likely develop from inside the structuretoward the frontUncertain – vorticities, rotations making the front unstable to the GDINo scintillation!Slide12

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionSD Hankasalmi backscatterSlide13

GPS scintillation at TOI frontBackground Methodology Results Discussion ConclusionCase study of GPS scintillation at TOI front on 31 October 2011Notable phase scintillation at the leading gradient, no significant amplitude scintillationIncreases in the σϕ index are most likely due to TEC gradient and poor data detrendingNo evidence in favour of structuring (significant enough to cause GPS scintillation) on the TOI front, or inside the high-density region immediately behind the gradientConclusion