Magnetic fluctuations in the Jupiter dusk magnetosheath: cassini observations

Abstract

Magnetic field fluctuations in the Jupiter dusk magnetosheath during the Cassini crossing in 2000-2001 are studied in this work. The properties of the turbulence in this magnetosheath interval are compared with those observed during a background solar wind interval using wavelet, Fourier, kurtosis and multifractal techniques. It was found that the variance of the magnetic field is much higher in the magnetosheath than in the solar wind by factors of 6 to 36 times. The kurtosis parameter was enhanced and larger than 3.0 for the BT and BN components in the magnetosheath, contrasted to the solar wind, which showed a sub-Gaussian behaviour. The multifractal spectrum showed a quasi Gaussian behaviour for the solar wind magnetic field and the occurrence of tails in the magnetic field distributions for the magnetosheath interval. The wavelet analysis showed that there are comparable periods of about 5 to 15 h in the magnetosheath and in the solar wind but these periods are intermittent or present local occurrences in the magnetosheath while they are more continuously observed in the solar wind. Finally, the Fourier power spectrum results showed higher spectral power for the magnetosheath magnetic field components, a power break at 3 mHz for the magnetosheath and solar wind data, with higher power indices in the high frequency portion of the spectra for the magnetosheath (absolute spectral indices varying from 2.3 to 2.7 at high frequencies) than for the solar wind (power index about 2.1). These results show quantitatively that the plasma turbulence is higher in the jovian magnetosheath than in the background upstream solar wind, due to the fact that as the continuous solar wind is compressed and heated at the bow shock, it becomes disrupted and turbulent.