IWF/ÖAW

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

1. Calibration of antennas on spacecraft by numerical simulations, rheometry, anechoic chamber measurements, and in-flight

2. 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

3. 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

Radio Waves

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IWF/ÖAW

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

Who are we?

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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

In-flight Calibration of STEREO/WAVES

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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

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

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Jovian Radio Emissions

STEREO Waves and Cassini RPWS spectra of Jovian periodic bursts [Panchenko et al.,

2013]

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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]

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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

Future Plans: 2015-2018

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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

Thank you

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