Flux, power, energy and polarization of Jovian S-bursts

The bandwidth, flux density, power, energy, and polarization of Jovian S-bursts are statistically analyzed from high-resolution dynamic spectral observations performed in Nançay using an acousto-optical spectrograph. Average values and ranges of variation are derived. The Io-Jupiter-observer configuration of our observations corresponds to S-bursts with dominant right-hand elliptical polarization. We obtain a bandwidth of 0.5–9 MHz, an average flux density of 4×10−20 W m−2 Hz−1 (normalized at 1 AU), and an average radiated power of ≈109 W. Instantaneous values cover up to 5 orders of magnitude around these averages. The S-burst flux densities are found to follow a power-law distribution, with an average index −2, subjected to abrupt variations at a timescale of minutes. The measured circular polarization ratio is V=−0.56, consistent with earlier measurements. Spectral variations of this polarization ratio are suggested by the observations, whose interpretation in terms of radio beaming angle is also consistent with earlier studies. The “density” of S-burst occurrence in the time–frequency plane is found to be ∼0.3. Finally, S- and L-burst energetics are compared, and variations of S-bursts physical properties as a function of Ioʹs longitude are searched for.