jovian anomalous continuum radiation

Jovian Anomalous Continuum Radiation

Sheng-Yi Ye1, D. A. Gurnett1, J. D. Menietti1, W. S. Kurth1, G. Fischer2

1The University of Iowa2Austrian Academy of Sciences

Cassini RPWS

HOM

JAC

nKOM

DAM

Persistent observation of JAC by Cassini after Jupiter flyby

Jupiter flyby

Cassini trajectory in Jupiter Solar ecliptic frame

2001

2004

Detection of JAC before SOI

JAC wave power falls off as a function of 1/r

Modulation of Jovian Anomalous Continuum

Jupiter flyby

Comparison with bKOM and HOM

The modulation power of JAC is much higher than the other radio emissions.

The duration JAC is observed (2+ years) is much longer than that of bKOM and HOM (several months).

JAC is mostly observed after Jupiter flyby, whereas bKOM and HOM are observed both before and after the flyby.

Jupiter flyby

JAC

bKOM

HOM

Kaiser et al. [2004]. Cassini was at 18.6 LT, 5.6 AU from Jupiter. Ulysses was at 8.8 LT, 2.4 AU from Jupiter.

Simultaneous observations of Jovian Anomalous Continuum

Hospodarsky et al. [2004].

Simultaneous observations by Cassini and Galileo

Solar wind

Solar wind

Hospodarsky et al. [2004].

Solar wind

Magnetosphere

Total apparent polarization degree = 0.JAC is unpolarized

QP bursts are highly circularly polarized. Opposite to the circular polarization sense of DAM.

Magnetosheath waveguide for JAC

Frequency change of JAC reflects change of fpSW at Jupiter

Conclusions

Jovian anomalous continuum near 10 kHz was consistently detected by Cassini RPWS after the Jupiter flyby for more than two years.

Wave power versus radial distance analyses revealed a 1/r dependence which is consistent with a linear source rather than a point source.

The rotational modulation analyses show that Jovian anomalous continuum is modulated like a clock at the system III period of Jupiter.

A leaky wave guide mechanism is proposed, where QP bursts wave energy is channeled down the magnetotail of Jupiter and reradiated by the magnetosheath.

The polarization characteristics of Jovian anomalous continuum are consistent with the leaky wave guide model, where the magnetosheath depolarizes the L-O mode waves through multiple reflections.

The frequency of the Jovian anomalous continuum is controlled by solar wind plasma density. So the observation of the Jovian anomalous continuum can be used as a remote diagnosis of the solar wind condition at Jupiter.