Ionospheric HF radars Pasha Ponomarenko. Outline Conventional radars vs ionospheric radars...

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Transcript of Ionospheric HF radars Pasha Ponomarenko. Outline Conventional radars vs ionospheric radars...

  • Ionospheric HF radarsPasha Ponomarenko

  • OutlineConventional radars vs ionospheric radarsCollective scatter processesAspect angle effectsHF propagation featuresSuperDARN

  • RadarsRAdio Detection And RangingRemote sensing tool based on EM wave emission and its reflection/scatter from a targetMain target parameters:range time of flightdirection antenna directivityvelocity Doppler shift

  • GroundNormal radarstargetThe target is usually smaller than the spatial pulse length.

  • Ionospherewith irregularitiesGround~300 kmIonospheric radarsThe scattering volume is larger than the spatial pulse length.

  • Collective scatter theory /2irregularitiesConstructive interference(Bragg condition)Spatial array with l = /2

  • Ionospheric turbulenceContinuous spatial spectrum of irregularities

  • Bragg scatter still works!/2Constructive interference condition(Bragg condition)

  • Anisotropic turbulenceE and F region irregularities are aligned with the background magnetic field

  • Dipole antenna with l >>

  • Aspect conditionsphase front

  • HF PropagationRadarHF: fN ~ f010-20 MHz

  • SuperDARNSuper Dual Auroral Radar Network

  • Dual Radar Network

  • Things to remeber:Backscatter signals are produced by plasma structures with Bragg scale sizes, l = /2Most of the backscatter power comes form areas where the radio wave propagates orthogonally to the geomagnetic field, k B0HF signals are capable of over-the-horizon propagation due to consecutive reflections from the ionosphere and the ground

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