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Radio Waves

Radio Waves. Main task Investigate radio emissions of magnetospheric and atmospheric processes with ground- and space-based radio antennas including calibration of the antenna systems Main research topics

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Radio Waves

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  1. Radio Waves Main task • Investigate radio emissions of magnetospheric and atmospheric processes with ground- and space-based radio antennas including calibration of the antenna systems Main research topics • Calibration of antennas on spacecraft by numerical simulations, rheometry, anechoic chamber measurements, and in-flight • Radiophysics of magnetized planets and the Sun: Solar radio emissions, Auroral kilometric radiation (AKR) at Earth, Jovian hectometric (HOM) and decametric (DAM) emission, Saturn kilometric radiation (SKR) and narrowband emissions • Radio emissions from lightning on planets with focus on Saturn Refereed publications (since Jan 2013) • Total: 12 (first author: 2) Educational activities (since Jan 2013) • 1 completed master thesis • 1 ongoing doctoral thesis IWF/ÖAW

  2. Who are we? Lead: Georg Fischer • Staff: M. Boudjada, M. Kapper (50%), J. Pagaran, M. Panchenko, (M. Sampl left, H.O. Rucker retired) • Students: PhD: C. Weber;Master: G. Rief (thesis completed) Cooperation within IWF • Exoplanetary radio emissions (Lammer et al., Khodachenko et al.) • Auroral and magnetospheric processes(Nakamura et al.) • Instrument developers (Steller et al.), Solar Orbiter RPW Key external collaboration USA: Dept. of Physics & Astronomy/Univ. of Iowa, Caltech Pasadena, Hampton Univ., NASA-GSFC; France: LESIA Meudon, LATMOS CNRS Guyancourt; Germany: Univ. Dresden, Astrophysical Inst. Potsdam; Ukraine: Inst. for Radio Astronomy; Russia: Inst. of Applied Physics/RAS; Sweden: Swedish Inst. of Space Physics IWF/ÖAW

  3. Anechoic Chamber Measurements • Solar Orbiter hardware model 1:50 for anechoic chamber measurements of RPW antenna system • Measurements of antenna pattern from 8-20 MHz (400-1000 MHz in chamber) and antenna S-parameters • Construction of a corresponding pre-amplifier for model • Numerical computer simulations with FEKO to gain surface currents on patch model, calculate antenna parameters (effective lengths, impedances), modeling of antenna heating circuit& influence of radii, comparison with anechoic chamber results • Solar Orbiter launch planned for Jan 2017 IWF/ÖAW

  4. In-flight Calibration of STEREO/WAVES • Effective length vectors were determined using the terrestrial AKR observed in early stage of STEREO mission during roll maneuvers • Least squares method combined with a genetic algorithm was applied to fit the best physical model to the observations • Accurate results confirm the results of rheometry(experimental method with model in electrolytic tank) and numerical wire-grid simulation • Our effective length vectors are recommended as a basis for future evaluation of SWAVES data (direction-finding & polarization) STEREO configuration (upper left), dynamic spectra of AKR recorded by STEREO-B during roll maneuvers (lower left) and modeled signals (red lines) compared to observations (right) [Panchenko et al., 2014] IWF/ÖAW

  5. Jovian Radio Emissions • Periodic bursts of non-Io DAM: • Period ~10.07 h (~1.5% longer than Jupiter System III rotation) • Correlation with solar wind • Possible origin: interchange instability in the Io plasma torus triggered by solar wind pulses • Investigation of Io plasma torus: • Occultation of hectometric emission • Radio remote sensing of Io plasma ribbon & estimation of electron density • Study of local time dependence STEREO Waves and Cassini RPWS spectra of Jovian periodic bursts [Panchenko et al., 2013] IWF/ÖAW

  6. Ground-Based Radio Observations • Detection of periodic Jovian bursts from the ground • Simultaneous long lasting observations using STEREO/WAVES and the ground-based radio telescope URAN-2 (Poltava, Ukraine) • Non-Io DAM periodic bursts observed up to 25 MHz with resolution of fine structures • Bursts observed with LH & RH circular polarization components from both hemispheres • Detection of Saturn lightning from the ground • First ground-based detection of Saturn lightning with UTR-2 radio telescope (ON-OFF beams) • Good agreement with Cassini/RPWS lightning observations despite radio interferences • High temporal resolution observations indicate similar structures of Saturn lightning to terrestrial intracloud lightning [Konovalenko et al., 2013] IWF/ÖAW

  7. Evolution of the Great White Spot • GWS (Great White Spot) is a large scale disturbance in Saturn’s atmosphere (a giant thunderstorm, where we detect lightning radio emissions with the Cassini RPWS instrument) • Lightning flashes detected from 5 Dec. 2010 to 28 Aug. 2011 • Five GWS events in history: 1876, 1903, 1933, 1960, 1990 • GWS consists of head (~10,000 km in latitude, lightning activity with rate ~10 s-1), and tail (300,000 km around Saturn) • Head spawned anticyclonic vortices and flashes were optically observed in blue light on dayside (in cyclonic gaps) • Large anticyclonic vortex (AV) collided with head in mid-June 2011 leading to decrease in flash rate and final demise • Total lightning power: 1013 W, Storm total power: 1017 W [Dyudina et al., 2013] IWF/ÖAW

  8. Future Plans: 2015-2018 • Antenna calibration • Antenna optimization studies for RPWI of JUICE • Solar Orbiter antenna calibration with rheometry • Solar & planetary radio emissions • Stereoscopic space- and ground-based observations of Jovian DAM and Solar radio emissions (Stereo WAVES, Juno, Solar Orbiter) • Ground-based radio observations (UTR-2, NenuFAR, LOFAR) with search for exoplanetary radio emissions • Long-term behavior of Saturn kilometric radiation and narrowband radio emissions (Cassini RPWS) • Lightning radio emissions • Continued analysis of Saturn lightning • Radio Wave Group has Co-I ships of Cassini/RPWS, Stereo WAVES, Solar Orbiter RPW and JUICE RPWI (data access) IWF/ÖAW

  9. Thank you IWF/ÖAW

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