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

3. Why does Jupiter have a magnetic field?  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 Physical Background  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?

4.  74 MHz observations made September 19 th and 20 th, 1998  330 MHz observations made September 15 th, 16 th, 19 th, and 20 th, 1998  Observations made with VLA in its B-configuration (74 MHz resolution ~ 2.3 arcmin, 330 MHz resolution ~ 17 arcsec) Frequency [MHz] S [Jy] Sept. 15 th Sept. 16thSept. 19thSept. 20thAverage 74N/A 4.96 ±0.304.71 ±0.304.84 ±0.16 3305.15 ±0.065.27 ±0.065.12 ±0.065.02 ±0.065.13 ±0.05 Jupiter’s nonthermal flux densities scaled to 4.04 AU Low-Frequency Observations

5.  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 Full Radio Spectrum

6. Model Fits  Radial (L) dependence governed by diffusion theory, of which the controllable parameters are the diffusion coefficient D 0, and the loss term,  0.  JUST the energy dependence of j(E, ,L)

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