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Low-Frequency VLA Observations of Jupiter

Low-Frequency VLA Observations of Jupiter. Imke de Pater, University of California – Berkeley Brian J. Butler, National Radio Astronomy Observatory Icarus 163 (2003) 428-433. Presented by Carl Gross TERPS Conference College Park, MD December 7, 2003. Jupiter’s Radio Spectrum.

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Low-Frequency VLA Observations of Jupiter

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  1. Low-Frequency VLA Observations of Jupiter Imke de Pater, University of California – Berkeley Brian J. Butler, National Radio Astronomy Observatory Icarus 163 (2003) 428-433 Presented by Carl Gross TERPS Conference College Park, MD December 7, 2003

  2. Jupiter’s Radio Spectrum • Below ~40 MHz: Decametric emission • Between 50 – 5000 MHz: Synchrotron emission • Above ~15000 MHz: Thermal emission

  3. Physical Background Why does Jupiter have a magnetic field? • High pressure ionizes hydrogen, forming a layer of plasma • Electrons are free to move freely through the plasma, like a metal, making it liquid ‘metallic’ hydrogen • These electrons move with Jupiter’s rotation, setting up a current, resulting in a magnetic field Synchro-what radiation? • Charged particles from the solar wind get trapped and accelerated along magnetic field lines, emitting synchrotron radiation • Recent observations and computer simulations show that Jupiter’s synchrotron emission can depend on solar activity, resulting in a time-varying radio spectrum • As a result, an accurate spectrum can only be obtained with simultaneous observations

  4. Low-Frequency Observations • 74 MHz observations made September 19th and 20th, 1998 • 330 MHz observations made September 15th, 16th, 19th, and 20th, 1998 • Observations made with VLA in its B-configuration (74 MHz resolution ~ 2.3 arcmin, 330 MHz resolution ~ 17 arcsec) Jupiter’s nonthermal flux densities scaled to 4.04 AU

  5. Full Radio Spectrum • In an effort to generate and accurate radio spectrum, throughout September 1998, 11 additional flux densities were measured for Jupiter, using 10 different telescopes • Frequencies range from 74 MHz – 8 GHz

  6. Model Fits • JUST the energy dependence of j(E,a,L) • Radial (L) dependence governed by diffusion theory, of which the controllable parameters are the diffusion coefficient D0, and the loss term, t0.

  7. Bibliography de Pater, I., Butler, B.J., 2003. Low-frequency VLA observations of Jupiter. Icarus 163, 428-433 de Pater, I., Bulter, B.J., Green, D.A., Strom, R., Millan, R., Klein, M.J., Bird, M.K., Funke, O., Neidhofer, J., Maddalena, R., Sault, R.J., Kesteven, M., Smits, D.P., Hunstead, R., 2003. Jupiter’s radio spectrum from 74 MHz up to 8 GHz. Icarus 163, 434-448

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