Imaging Jupiter's radiation belts with HBA

Sebastien Hess
LOFAR Transients Key Project Meeting, Meudon, December 2011

Transcript

1. On-going work on imaging planetary radio emissions Sébastien Hess1, Cyril Tasse2, Julien Girard2, Philippe Zarka2 1 LATMOS, University Versailles St-Quentin, IPSL/CNRS, France 2 LESIA, Observatoire de Paris, CNRS, France
2. Summary of the planetary emissions Although most of planets emit, Jupiter is the only visible from the ground. Exception : Lightning related emissions (But we won't image lightnings on Saturn)
3. Principal target for imaging : Jupiter Huge magnetosphere Emissions everywhere, but observable ones are close to the planet. But LOFAR on the moon would observe larger part of the magnetosphere.
4. Two main targets for imaging at Jupiter : Auroral emissions @ the local electron cyclotron frequency (below 40MHz) Radiation belts, synchrotron emissions, dominant above 50 MHz
5. Two main targets for imaging at Jupiter : Auroral emissions @ the local electron cyclotron frequency (below 40MHz) Radiation belts, synchrotron emissions, dominant above 50 MHz First target for several reasons : Higher frequencies (HBA) Wider target (easier to resolve) No time evolution other than due to planetary rotation
6. Previous images by VLA ` Detection only (no image) 1.4 GHz /20 cm 333 MHz / 90 cm 74 MHz 6 cm [Bolton et al., 2002]
7. Why should we image them with LOFAR (Other than to test the imaging routines) Emission frequency related to electron energy : Image at different frequencies = Distribution of electrons of different energies. Knowing the distribution of electrons with different energies needed to understand the origin and transport of the electrons in the Jovian radiation belts. [Cassini obs. @ 2 cm]
8. On-going work.... Observations made with LOFAR on Nov, 10th, 2011. 18:24 to Nov,11th. 4:24 20 core stations + 9 remote stations Field + calibration beams. Calibration beam gives flux and timer calibration No ionosphere calibration yet. (temporary to have something to show) Improvement expected with better calibrations. f=127 MHz
9. On-going work.... Comparison with VLA f=127 MHz Observations made with LOFAR on Nov, 10th, 2011, 18:24 to Nov,11th, 4:24 20 core stations + 9 remote stations Field + calibration beams. Calibration beam gives flux and timer calibration No ionosphere calibration yet. (temporary to have something to show) Improvement expected with better calibration. (PS : blurry but already the lowest frequency resolved image of the Jovian radiation belts)
10. Future Jupiter rotates in 9h 55 min : possible to sample a large range on longitude in one observation using tomographic methods  3D reconstruction 3D model of the radiation belt over a large (and continuous) ranges of enregies [de Pater et al, 2005]
11. Future Jupiter rotates in 9h 55 min : possible to sample a large range on longitude in one observation using tomographic methods  3D reconstruction 3D model of the radiation belt over a large (and continuous) ranges of enregies Prolongate the work to LBA frequencies. Do some science with it. Image auroral emissions [de Pater et al, 2005]