ULF waves in the Io torus: ULYSSES observations - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Geophysical Research Space Physics Année : 1993

ULF waves in the Io torus: ULYSSES observations

Résumé

Throughout the Io torus, Ulysses has observed intense ultralow frequency (ULF) wave activity in both electric and magnetic components. Such ULF waves have been previously suggested as the source of ion precipitation leading to Jovian aurorae. The peaks of the wave spectra are closely related to the ion cyclotron frequencies, which is evidence of the waves being ion cyclotron waves (ICWs). Analysis of the dispersion relation using a multicomponent density model shows that at high latitudes (approximately 30 deg), peak frequencies of the waves fall into L mode branches of guided or unguided ICWs. Near the equator, in addition to the ICWs below fcO(2+), there are strong signals at approximately 10 Hz which require an unexpectedly large energetic ion temperature anistropy to be explained by the excitation of either convective or nonconvective ion cyclotron instabilities. Their generation mechanism remains open for the future study. Evaluation of the Poynting vector and the dispersion relation analysis suggest that the waves near the equator had a small wave angle relative to the magnetic field, while those observed at high latitudes were more oblique. The polarization of the waves below fcH(+) is more random than that of the whistler mode waves, but left-hand-polarized components of the waves can still be seen. The intensity of the ICWs both near the equator and at high latitudes are strong enough to meet the requirement for producing strong pitch angle scattering of energetic ions.
Fichier principal
Vignette du fichier
ark _67375_WNG-H4K10NZG-9.pdf (1.09 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

hal-00408544 , version 1 (03-02-2021)

Identifiants

Citer

Naiguo Lin, P. J. Kellogg, R. J. Macdowell, Y. Mei, N. Cornilleau-Wehrlin, et al.. ULF waves in the Io torus: ULYSSES observations. Journal of Geophysical Research Space Physics, 1993, 98 (A12), pp.21151-21162. ⟨10.1029/93JA02593⟩. ⟨hal-00408544⟩
72 Consultations
49 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More