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Saturn's quasiperiodic magnetohydrodynamic waves
Author(s) -
Yates J. N.,
Southwood D. J.,
Dougherty M. K.,
Sulaiman A. H.,
Masters A.,
Cowley S. W. H.,
Kivelson M. G.,
Chen C. H. K.,
Provan G.,
Mitchell D. G.,
Hospodarsky G. B.,
Achilleos N.,
Sorba A. M.,
Coates A. J.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl071069
Subject(s) - physics , saturn , quasiperiodic function , magnetosphere , geophysics , amplitude , magnetohydrodynamic drive , magnetic field , oscillation (cell signaling) , astrophysics , magnetohydrodynamics , condensed matter physics , quantum mechanics , planet , biology , genetics
Quasiperiodic ∼1 h fluctuations have been recently reported by numerous instruments on board the Cassini spacecraft. The interpretation of the sources of these fluctuations has remained elusive to date. Here we provide an explanation for the origin of these fluctuations using magnetometer observations. We find that magnetic field fluctuations at high northern latitudes are Alfvénic, with small amplitudes (∼0.4nT), and are concentrated in wave packets similar to those observed in Kleindienst et al. (2009). The wave packets recur periodically at the northern magnetic oscillation period. We use a magnetospheric box model to provide an interpretation of the wave periods. Our model results suggest that the observed magnetic fluctuations are second harmonic Alfvén waves standing between the northern and southern ionospheres in Saturn's outer magnetosphere.